Harvard University LTER and NIGEC Programs

Abstracts from the 15th Annual Harvard Forest Ecology Symposium 29 March 2004

On the cover: Chronic nitrogen inputs lead to conifer forest decline in the nitrogen saturation experiment, which began 15 years ago at the Harvard Forest. Foliar biomass has been greatly reduced in the pine stand receiving high-N additions (bottom) compared with the control (top). Photographs by D.R. Foster.

LONG TERM ECOLOGICAL RESEARCH AT HARVARD FOREST

March 29, 2004

Audrey Barker Plotkin, Julie S. Pallant and Linda Hampson, Editors

Long Term Ecological Research at Harvard Forest

Background and Framework for Long-Term Research- - - - 1

Design of the Harvard Forest Long Term Ecological Research Program- - 9

Education Integrated with Research ------13

National Institute for Global Environmental Change (NIGEC) - - - 13

Site and Facilities ------14

Literature Cited ------17

Harvard Forest Ecology Symposium

Titles of Abstracts ------20

Contributors ------23

Abstracts ------27

Publications of the Harvard Forest LTER ------136

Acknowledgement of Support ------168

LONG-TERM ECOLOGICAL RESEARCH AT HARVARD FOREST

Background and Framework for Long-Term This long-term approach to ecological Research research was a central driver in the selection of research directions when we teamed together with In 1907 Harvard University acquired colleagues from several Harvard departments, the nearly 3,000 acres of land in the central University of New Hampshire, the Ecosystem Massachusetts town of Petersham to establish the Center at the Marine Biological Laboratory, and Harvard Forest as a center for research and the University of Massachusetts in 1988 to form education in forest ecology, conservation, and the Harvard Forest Long Term Ecological management. In the ensuing century of Research (LTER) program. In particular, we investigations, students, faculty, and visiting applied our understanding of the history of the researchers came to rely heavily on accumulated land, modern forest dynamics, and projections for and continuing historical studies as a complement future changes in the regional and global to intensive field and laboratory work and as a environment to select a suite of important source of insight into important processes that disturbances, stresses, and forest ecosystem have shaped the land, its people, and its biota. By processes to investigate in detail. The broad developing long-term studies of the past and objective of these studies was to develop present, we can uncover events and processes that information and approaches that will answer are infrequent in occurrence, we can examine fundamental ecological questions and to generate physical and biological processes that unfold over data and perspectives that have broad application long periods of time, and we can sift through the to major environmental and conservation issues. many changes and factors that have operated in A sketch of the history of New England's the landscape over time in order to identify those land and people highlights the major changes that that are critical for interpreting modern conditions shape the present landscape and the key objectives and dynamics (Figure 1, Table 1). of our investigations.

Table 1. Design of the Harvard Forest LTER Program Research Approaches 1. Reconstruction of ecosystem dynamics using paleoecology, historical ecology, and modeling to evaluate long- term trends, to study infrequent processes, and to understand the development of modern conditions. 2. Measurement of modern ecosystem structure, composition, processes, and dynamics on permanent plots, through remote sensing, and through eddy flux measurements of atmosphere-biosphere exchanges to define current conditions and rates. 3. Experimental manipulations of ecosystems and controlled environment studies on individual plants and populations to evaluate and compare patterns of response and to collect integrated measurements on multiple processes. 4. Integration through modeling, comparative studies, regular meetings, annual symposia, and synthetic publications. 5. Application to ecological theory, conservation biology, environmental policy, and forest management.

Spatial Scales of Investigation Disturbances, Stresses, and Environmental Processes 1. Site - 1 km - Harvard Forest Investigated 2. Landscape - 10 km - Petersham, MA 1. Climate change 3. Sub-region - 100 km - Central Massachusetts 2. Hurricane and lesser windstorms 4. Region - 1000 km - New England and New 3. Fire York 4. Native and introduced pathogens 5. Land-use: aboriginal, Colonial, and current 6. Changes in atmospheric chemistry and deposition. Education Integrated with Research 1. Summer Research Program for Under-graduates and Graduate Students (15-20 students/yr) 2. Informal Education Program through the Fisher Museum (> 5,000 visitors/yr) 3. Graduate Programs through diverse institutions at the MS and PhD level (5-15/yr) 4. Bullard Fellowship Program for mid-career scientists (4-8/yr) 5. Conferences, Symposia and Workshops (> 1000 participants/yr)

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Figure 1. Spatial scales of investigation in the Harvard Forest LTER program.

2 Overview of Environmental and Forest Dynamics controlling vegetation structure and composition in Central New England (Foster and Boose 1995). Long-term records and The landscape of central New England the ubiquitous presence of mound and pit has been highly dynamic over the past few topography in old forest stands suggest that finer- thousand years as environmental factors that scale disturbances such as gap dynamics, control forest structure, composition and downbursts and tornadoes have contributed more ecosystem processes have changed continuously, local patterning to forests over the ages. The though at variable rates (Figure 2; Foster and relative role of these different types and scales of Zebryk 1993, Fuller et al. 1998). The broad-scale physical disturbance and their spatial distribution physiographic template has been relatively across the landscape and region are largely unaltered since the last glaciation shaped the unknown. gentle hill and valley topography and left a Although infrequent, perhaps occurring as variable thickness of till and stratified deposits rarely as once every thousand years in some some 13,000 years ago. However, climate, on a regions and forest types, or ten times as frequently century to millennial time frame, has undergone in others, fire has played an uncertain and variable continual change in temperature, precipitation and role in New England forests (Fuller et al. 1998, their seasonal distribution. Even over the last Parshall and Foster 2002). The topic of fire century there exist annual variation, short-lived invariably introduces the role of humans, for it is changes, and lengthy trends that are relevant to in the purposeful use of fire that aboriginal people forested ecosystems, and the physical processes may have exerted a widespread, though subtle and biotic constituents that shape them (Aber et impact on natural vegetation. For the New al. 1995). England region the general patterns of aboriginal Reconstruction of forest dynamics suggest activity are well known: a highly variable that natural disturbance processes, ranging from geographic pattern with dense settlements on the frequent small events to infrequent large and coast, coastal islands, and along major river catastrophic impacts have played an important valleys and sharply lower population in upland role in structuring the pattern and processes of areas; a dynamic history of changing cultural natural ecosystems across New England (Foster patterns, seasonal activities and density that varied 1988a). Nearly 5000 years ago a remarkably with climate and major changes in forest abrupt and major decline in hemlock occurred composition that altered the availability of throughout its range in New England and across important food sources such as nut-bearing trees the Northeast, presumably as a consequence of and wildlife; and the late introduction of maize infestation from a novel pathogen. Over the agriculture within the past 1000 years subsequent 1000-year period forest ecosystems (Mulholland 1984, 1988). Much speculation underwent pronounced changes as hemlock exists on how these geographic and temporal gradually recovered, although with considerable patterns of activity interacted with and altered the regional to local variation in the response and natural ecosystem patterns. In particular, the recovery patterns (Fuller et al. 1998). The extent of forest clearance for agriculture and the historical record of major hurricane impacts every role of fire in pre-European times remain a major 75-100 years leads to speculation that infrequent issue. catastrophic disruption by tropical storms may Over the past 350 years since European play an important role in structuring the forest settlement the rate of ecosystem change has vegetation of New England over long time periods accelerated and the landscape of New England has (Figures 3 and 4; Boose et al. 1994, 2001). Given been transformed (Foster et al. 1998, Hall et al. the propensity for such storms to weaken over 2002). Despite a steadily increasing human land and to exhibit relatively constrained patterns population, major cultural and technological shifts of movement across New England, it is quite have led to a region-wide historical pattern of possible that pronounced regional gradients and extensive deforestation through the mid to late specific landscape-scale patterns of historical 19th century followed by broad-scale impact may interact with broad-scale abandonment of agriculture and massive natural environmental and physiographic patterns in reforestation (Figures 5 and 6). Vast areas of New

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Figure 2. The temporal setting for long-term studies in New England in relation to important biotic, cultural, and environmental changes. Biotic (vegetation) change (top) is illustrated by the varying percentages of pollen of major plant taxa from Aino Pond in north central Massachusetts (Fuller et al. 1998). Major cultural changes (middle) highlight the shift from native hunting, gathering, and horticulture to European agriculture and industry. Climate dynamics (bottom) are depicted by the long-term change in Northern Hemisphere temperature over the past 1,000 years, as reconstructed from tree-ring records and other proxies (adapted from Crowley 2000, data archived at the World Data Center for Paleoclimatology, Boulder, Colorado, USA).

4 England that once supported scattered, cut-over comparative impact of these novel stresses with woodlots in a matrix of fields and pastures are historically important disturbance processes is a now covered with aggrading second-growth forest major issue for ecologists and concern for natural that ranges across 65-85% of the uplands. resource managers. Excluding northern Maine, the new forests of the As we seek to understand the current New England states bear much evidence of the structure, composition, and process of forest agricultural past of pasture, cropland, and ecosystems in central New England it is essential woodlot: stonewalls separating contrasting forest that we develop a perspective that incorporates the stands, old cellar holes and collapsed dams, and historically important as well as currently wood trails and dirt road remnants of colonial operative environmental factors that control these transportation networks. As the forest area and ecosystems (Foster et al. 1992, 1996). It is also size have recovered regionally so have the native important to frame questions and approaches that fauna and regional ecosystem processes (Motzkin are regionally and societally relevant and that et al. 1996, 1999, Compton et al. 1998, Compton have general applicability to the understanding of and Boone 2000). In many ways the landscape of terrestrial forest ecosystems. rural New England appears more natural than at any time since the 1700s. The major question that Broad Ecological Questions Concerning New looms is: how has this massive land-use England Forests disturbance altered the natural forest pattern and Our brief historical overview highlights process and what legacies has it left in the new many changes in the physical, biotic, and human forest landscape? environment of New England that have initiated a In recent decades the forests and range of forest dynamics and have set the environment of New England have been exposed vegetation and landscape on a long-term to more novel types of anthropogenic stress. A trajectory. This overview also raises broad series of introduced pathogens - chestnut blight, questions that drive our research as we seek to Dutch elm disease, gypsy moth, beech bark understand, conserve, and manage the modern disease, and hemlock woolly adelgid - has landscape and anticipate future changes. Not selectively weakened, defoliated or decimated surprisingly, these questions address fundamental major tree species across the region (Figure 7; issues relevant to many natural ecosystems Orwig 2002). Industrialization has led to worldwide. pronounced changes in the earth's atmosphere that 1. How does the array of environmental are leading to increased, though geographically factors and disturbance processes interact to variable, deposition of nitrogen (a major limiting shape forest ecosystems over time? The preceding nutrient in most terrestrial ecosystems) and section identified major uncertainties concerning sulphur in forms that acidify precipitation as well the ways in which climate change, natural as the ecosystems that they impact (Figure 8; Aber disturbance, and human activities have operated at et al. 1993, 1997). While photochemical reactions local to regional scales through time. Of specific in the upper atmosphere deplete the tropospheric interest are details of the natural disturbance ozone layer that shields the earth from ultraviolet regimes, especially variations in wind, pathogens, radiation, stagnant circulation patterns during the and fire and the way in which these have summer growing season bring damaging ozone interacted with prehistoric and historical human episodes up the east coast to interior New England activity and environmental change. forests (Goulden et al. 1996; Munger et al. 1996). 2. What are the contrasting effects of Increases in major greenhouse trace gases - CO2, natural, physical disturbance versus novel, CH4, and N2O may be leading to a regional annual anthropogenic stress on the function of forest increase of temperature of 3-4oC within the next ecosystems? Increasingly, forest ecosystems are century. Meanwhile, the increase in CO2 (as well exposed to chemical and climatic stresses that are as N and O3) may be having subtle, though qualitatively different from the types of impacts important, consequences on plant performance that forests have experienced for millennia. and ecosystem processes (Bazzaz and Miao 1993; Recognizing that forest species evolved within a Bazzaz et al. 1996). The interaction and context of natural disturbance and environmental

5 Figure 3. Paths of major hurricanes that have affected New England and the Harvard Forest during the historical period.

Figure 4. Forests damaged by the 1938 Hurricane were also changed by the massive salvage effort that followed. Photograph from the Harvard Forest Archives.

6 Figure 5. Forest cover and population trends for New England.

Figure 6. Change in forest cover in Massachusetts from 1830 to 1999.

7 Figure 7. Hemlock woolly adelgid infestation and the range distribution of hemlock across the eastern United States (USDA 2002).

N Deposition (kg ha-1 yr-1) Figure 8. Geographic pattern of atmospheric 3.0 nitrogen deposition across New England. Concentrations of 5.5 nitrogen are strongly related to westerly air flow from major 8.0 sources of human production of nitrogen elevation which 10. 5 controls precipitation that contains nitrogen compounds (Ollinger et 13.0 al. 1995).

8 change, it is important to assess whether forests Design of the Harvard Forest Long-Term retain the same degree of control over ecosystem Ecological Research Program processes (for example, nutrient cycling, hydrology, and forest growth) under these novel In order to address the broad ecological conditions as they do under historically important questions raised above, our research effort has stresses. Specifically, we are interested in been organized to integrate studies across contrasting the relative effects of physical disciplines, scientific approaches, and a range of disturbance such as hurricane with important new spatial and temporal scales. By augmenting the stresses such as nitrogen additions and rapid lengthy record of ecosystem change that had climate change. developed over nearly a century of study at the 3. What changes in forest patterns and Harvard Forest, we have selected historically processes were generated by the history of important and relevant processes for investigation. intensive land use since European settlement, and We have also expanded existing programs in how persistent are the physical and biological order to make education and public outreach a legacies of this historical disturbance in New major goal of our program. England's reforested landscape? Large areas of We use a suite of scientific approaches in northwestern Europe, Latin America, and eastern order to identify important ecological processes to North America have experienced or are currently create a long-term series of measurements and to undergoing landscape transformations analogous assess ecosystem response and dynamics. to the forest-deforestation-reforestation history of Ecological history provides information New England, and thus lessons from our region on the range of environmental conditions and should have general relevance. Major questions types of natural and human disturbance processes remain concerning the initial effects of colonial that have been historically important in a land-use activity, the ability of forest ecosystems landscape. This information identifies processes to return to predisturbance conditions, and the that are critical to study in order to understand legacy of historical changes on modern forest ecosystem structure and function, and it characteristics. For example, is the history of sites contributes to our understanding of the relative that were in agriculture 150 years ago reflected in role of historical factors versus environmental the modern forest composition, soils and fertility, factors in controlling modern conditions. In or the way that the forest will respond to the next addition, many key ecological processes, such as hurricane or to acid rain? succession, ecosystem development, large 4. What application do answers to these disturbances, species invasion, and ecosystem questions have for environmental policy issues response to environmental change, operate on such as (a) designing effective local and regional decadal to millennia timescales or with such great conservation strategies, (b) anticipating forest temporal variability that they are difficult or ecosystem response to modern stresses and impossible to measure through conventional disturbances, and (c) developing global strategies studies. Historical techniques enable the to mitigate future climate change? As we develop evaluation of such processes and allow these an improved understanding of modern forest observations to be placed within the context of ecosystems and their history of change, we can long-term trends and cycles of environmental bring this information to bear on fundamental change. ecological questions concerning the patterns and Experimental field manipulations allow us processes of natural ecosystem organization and to evaluate infrequent though historically dynamics. We can also assist in the application of important processes as well as to anticipate future this information to education and the management ecosystem response to predicted changes in of our natural environment and resources. climate or chemical stresses. At the Harvard Forest, we have focused large experiments on a subset of important though contrasting disturbances and stresses, including simulation of windthrow from an intense hurricane, timber harvesting, chronic nitrogen amendments to

9 simulate enhanced deposition of nitrogen, soil U.S. Forest Service and in the enhanced warming as a component of climate change, and deposition of nitrogen that is occurring at high alteration of organic matter inputs to soils to elevations in New England and in central Europe; examine basic soil processes linked to carbon and the soil warming experiment has been replicated nitrogen dynamics. In the case of historically in the subarctic region at the Abisko Research important processes such as hurricanes and forest Station in northern Sweden; organic matter logging, results from the experimental manipulation experiments have been undertaken manipulations are compared directly with long- at the University of Wisconsin and other sites term studies of "natural experiments," such as the within the U.S. LTER network; and results from 1938 hurricane or historical logging that occurred the experimental hurricane have been compared throughout central New England. Many of the with those from natural events in many temperate experiments are compared with parallel studies in and tropical forests. In all cases, the integrated different ecosystems. For example, the nitrogen measurements of ecosystem structure and pattern saturation experiment has counterparts at the Bear enable comparison among these important Brooks watershed in Maine maintained by the manipulations.

Table 2. Spatial Scales and Research Approaches of Harvard Forest Studies. REGION SUB-REGION LANDSCAPE SITE Area New England C. Massachusetts Petersham Harvard Forest Size 1000 km 100 km 10 km 1 km Elevation 0 – 1870 m 30 – 610 m 190 – 425 m 280 – 425 m RECONSTRUCTION Paleoecology * * * * Archaeology * * * History * * * * Dendrochronology * * * Hurricane Modeling * * * * Ecosystem Modeling * * * *

MEASUREMENT Vegetation Surveys * * * * Soil Surveys * * Fauna/Flora * * Remote Sensing * * * Atomosphere-Biosphere Exchange *

EXPERIMENTAL MANIPULATION Hurricane Pulldown * Nitrogen Saturation * Soil Warming * Organic Matter * Controlled Environment * Hemlock Removal *

APPLICATION Atmospheric Deposition * * * * Water Management * * * * Forest Management * * * * Land Protection * * * Land Use Planning * * * Education * * * *

Long-term measurements of ecosystem particular, measurements continued over decades patterns and processes in a range of natural forests assess seasonal and interannual variation, long- carry forward observations of current conditions term trends and trajectories, and ecosystem and results from reconstructive studies. In function under highly varied sets of conditions.

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Permanent plots and repeated sampling of forest Many important processes, including stands at five- to ten-year intervals continue long- natural and human disturbance, wildlife term experiments and observations that were movement, and hydrologic flows, occur at a initiated in the early 1900s by the first faculty and landscape scale where physiography, slope students at the Harvard Forest. Remote sensing, position, vegetation structure, and soil variation using modern and historical aerial photographs or interact to form complex patterns. In central New satellite images, increases the coverage of many England, the area of an individual town (often measurements across two or more of our spatial approximately 10 by 10 kilometers) captures scales of observation (for example, from plots in a substantial landscape variation of the forest to the landscape or region) and over many characteristic hill and valley topography. decades. Control areas, which are the undisturbed Consequently, the town of Petersham, but monitored parts of our experimental Massachusetts, serves as one focus for many manipulations, provide baseline measurements landscape studies because it includes the main that may be linked with other data sets, such as tracts of the Harvard Forest and represents a the studies of atmosphere-biosphere exchange at typical rural village in the New England uplands. our Environmental Measurement Station. The Given the politically independent structure of coupling of retrospective historical studies and New England town governments, much of the long-term measurements of intact and geographical, social, and environmental data experimentally manipulated ecosystems provides relevant to ecological studies are collected or an integrated assessment of ecosystem dynamics aggregated by public agencies at a town level, and function under a range of historical, modern, making this political unit a particularly convenient and simulated conditions. scale of study. Harvard Forest research operates at four To place site- and landscape-level studies primary spatial scales of investigation: site in a broader context and to examine variation in (approximately 1 kilometer), landscape environmental, social, and biotic processes, we (approximately 10 kilometers), subregion conduct a considerable amount of research at the (approximately 100 kilometers), and region subregional scale (for example, central (approximately 1,000 kilometers) (Figure 1, Table Massachusetts, Cape Cod and the Islands, the 2). Intensive site studies at the scale of individual White Mountains of New Hampshire, the organisms, forests, or sample plots represent the Connecticut Valley), and the regional scale of heart of our long-term effort. Most of our studies New England, oftentimes including adjacent New at this scale occur on Harvard Forest land York. Selection of these areas is based on (approximately 1,200 hectares) in central ecological, cultural, and pragmatic considerations. Massachusetts where varied vegetation, site For example, the central Massachusetts subregion conditions, and history, along with nearly 100 (approximately 5,000 square kilometers) extends years of study, provide an ideal setting for long- 100 kilometers east from the Connecticut Valley term measurements and experiments (Figure 9). Lowland through the Central Uplands Infrastructure improvements, such as access to physiographic region to the Eastern Lowlands electrical and telecommunications cables at major west of Boston, and 50 kilometers south from the experiments, erection of a series of canopy access New Hampshire border approximately halfway to and environmental measurement towers, the use the Connecticut border. Petersham and the of mobile lifts to reach into the crowns of mature Harvard Forest lie directly in the center of this trees, and surveyed grid points, enable diverse diverse subregion, which encompasses a wide studies. Geographic information system-based range of the physical and biological variation in data management systems allow field sampling to central New England, as well as a substantial be integrated with other sources of information amount of the cultural variation that has occurred such as low-elevation aerial photography, satellite from Indian to modern times. The ability to place imagery, radiotelemetry, historical surveys, and intensive studies within the context of these major vegetation maps. cultural and environmental gradients is extremely useful for interpreting the generality of results and

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Hemlock Manipulation Plots

Figure 9. Major study sites at the Harvard Forest, Petersham, Massachusetts.

12 for understanding the broadscale controls over Education Integrated with Research major ecological processes. On the practical side, this subregion consists of fifty townships in four Interdisciplinary ecological research counties of one state, which presents a programs based at established field institutions manageable, though considerable, challenge for provide much more than insights into important the collection and archiving of archaeological, scientific questions; they also afford the historical, environmental, and biological data. opportunity to train the next generation of Information for this region comes in three primary scientists and to convey information to an forms – continuous spatial coverage (for example, interested public audience. Education thus forms elevation, land-cover maps, and remote sensing an essential part of the HF LTER program, imagery), township-level data (for example, providing both a means for developing science population, agricultural, and forestry statistics), or and an outlet for disseminating it. Students are networks of site-specific data (for example, directly integrated into our ecological studies. A sample plots, archaeological sites, and intensive summer research program brings 25-35 measurement locations). undergraduates and recent graduates to the Forest Considerably greater variation in to work on research projects, to undertake environmental and cultural conditions occurs independent studies, and to learn how science is across the New England region, and the dynamics conducted by large research groups representing and effects of many of the broadscale disturbances diverse institutions and composed of faculty, staff and anthropogenic stresses can be understood only and technical scientists, post-doctoral associates, at this scale. In order to evaluate processes that are graduate students, and administrators. Graduate relevant at the regional scale, we conducted select students from the MS and PhD programs of many studies utilizing diverse historical, modern, and northeastern universities pursue thesis studies as modeling approaches. These studies yield data part of this effort and the Bullard Fellowship that may be continuous, aggregated at the county Program for Forest Research at Harvard Forest scale, or site specific. Importantly, these studies annually enables 4-8 mid-career faculty and also enable us to see how well our approaches and professionals from around the world to interact results translate to other areas. with LTER researchers. Local K-12 classes also The research approach followed by the learn about ecological research through Harvard Forest LTER program is a continuation participation in the LTER Schoolyard program. of the long-standing approach to understanding Finally, permanent exhibits, scientific poster the New England landscape that Harvard Forest displays, and audio-visual programs at the Fisher researchers have used for nearly a century. We Museum expand on research results and inform use historical studies to understand the more than 5000 visitors annually about the natural development of modern forests and to study history and management of New England forests. infrequent and variable events and slow processes; we integrate our understanding of modern National Institute for Global Environmental measurements and experiments with results from Change (NIGEC) Northeast Regional Center retrospective studies; we emphasize long-term experiments with an informative and secure data The National Institute for Global management structure; and we attempt to Environmental Change is a funded activity of the synthesize the results of all of these studies such U.S. Department of Energy. NIGEC focuses its that they address fundamental ecological attention at a regional level by dividing the U.S. questions and provide insights into societally into six separate regions in order to take into relevant management issues. account geographical and geological diversity when researching the consequences of environmental change for the United States. Since the Institute's inception in 1990, its mission has been to assist the nation in its response to human- induced influence on the environment by pursuing

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excellent research in the field of global climate Long-term eddy flux observations at two change. The Northeast Region includes the states sites, Harvard Forest (Petersham, MA) and of Connecticut, Delaware, Maine, Maryland, Howland Forest (Howland, ME), provide the Massachusetts, New Hampshire, New Jersey, anchors for the program. These sites are the focus New York, Pennsylvania, Rhode Island and for a diverse set of manipulations (e.g., open-top Vermont. chambers, logging, soil warming, and nutrient The Northeast Regional Center (NERC) additions), ecological studies of forest has pioneered multi-disciplinary, coordinated development and invasive species, stable isotope studies of representative forest ecosystems in the measurements, analysis of meteorological and Northeast to quantify and understand the effects environmental observations, measurements of of forests on the atmosphere (especially concentrations and deposition of air pollutants, greenhouse gases such as CO2) and the effects of modeling, and historical and palynological the atmosphere on forests studies. They are the longest running of the (deposition of pollution and nutrients), both continuous eddy flux measurements in the regionally and globally. The program emphasizes AmeriFlux network, and have served as testing synthesis of long- and short-term observations, grounds to resolve methodological issues in long- manipulations, ecological and historical studies, term flux measurements. These issues continue to and modeling to address directly and be the subject of ongoing research. quantitatively the main factors that regulate forest NERC functions as a Science Team to processes. The studies span time scales from bring these diverse disciplines together. Scientists transient changes in environmental conditions supported by NERC communicate often and meet (hours) to climatic forcing and legacies of prior annually to review results and plan coordinated land use and disturbance (years, decades). work. All data are required to be shared with The strategic vision of the NERC NERC researchers soon after collection, at the emphasizes integrated research on ecological annual meeting, and with the public through the responses of forests to management, climatic NIGEC-NERC data archive (http://www- change, and environmental stressors (air pollution, as.harvard.edu/data/data.html) and the AmeriFlux inputs of nutrients, heavy metals, and acids, data archive invasive species such as the hemlock woolly (http://cdiac.esd.ornl.gov/programs/ameriflux/data adelgid). The main focus is on quantifying and 2.htm). The policy of maximum data sharing is understanding the structure, development, viewed as essential to success of the NERC productivity and net uptake or release of CO2 by strategic vision. forests of northeastern North America. An important supporting focus is on quantifying and Site and Facilities understanding emissions and deposition of pollutants, greenhouse gases, and ozone- The 1200-hectare Harvard Forest in destroying chemicals in the region. NERC north-central Massachusetts (Figure 1) has been emphasizes interdisciplinary research with process operated as a silvicultural and ecological research studies and modeling integrated within a facility by Harvard University since 1907. The framework of unique, long-term quantitative Forest lies in the New England Upland observations and manipulations. physiographic region, with moderate local relief The goals of NERC are to (1) investigate ranging from 220 m to 410 m above sea level. A carbon exchange of forest ecosystems, (2) study bedrock dominated by granite, gneiss, and schist the effects of climate change, disturbance by is generally overlain by sandy-loam glacial till pests, logging and severe weather, and air soils that are moderately to well drained, acidic, pollution on forest resources, (3) study of the and average 3 meters in thickness. Local effects of forests on regional air quality and variations in parent materials, textures, alluvial climate, and (4) quantification of emission and colluvial deposits, and slope produce poorly sources of greenhouse gases and ozone-destroying drained and excessively drained sites as well. The chemicals from the industrialized Northeast. regional climate is cool temperate (July mean

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20oC, January -7oC) and humid, with precipitation morphological, computational and GIS studies, (annual mean 110 cm) distributed fairly evenly and a complete herbarium of the local flora. The throughout the year. Torrey Laboratories include two research The Forest lies in the Transition greenhouses, offices, and physiology and nutrient Hardwood-White Pine-Hemlock forest region. analysis laboratories with fume hoods, gas Dominant species include red oak (Quercus chromatograph, Lachat autoanalyzer, CN rubra), red maple (Acer rubrum), black birch analyzer, nano pure water, balances, and drying (Betula lenta), white pine (Pinus strobus) and ovens. The Archives (2200 sq ft) houses 100 hemlock (Tsuga canadensis). On drier soils white years of data on the land and research, a sample oak (Quercus alba), black oak (Q. velutina), archive with cold storage facilities, and air photo hickory (Carya ovata) and, formerly chestnut interpretation systems. (Castanea dentata) increase. Cool, moist, but The woods crew and the forest manager well-drained sites support a northern mixed forest are equipped for experimental manipulations, of yellow birch (Betula alleghaniensis), beech forestry operations, construction, and (Fagus grandifolia), sugar maple (Acer maintenance. Large equipment including a saccharum), paper birch (Betula papyrifera), ash mobile canopy lift, back-hoe, bulldozer, tractor, (Fraxinus americana), hemlock and white pine, crawler, dump truck, flat bed truck, pick-up and whereas red spruce (Picea rubens), black spruce van, are stored in garages and in a 2400 sq ft pole (P. mariana) and larch (Larix laricina) occupy shed. The staff operates a wood-working shop oligotrophic peatlands. Approximately 7% of the which serves as the center for building Forest is occupied by plantations of diverse maintenance and a sawmill is operated seasonally. composition and age. Detailed stand records, The University owns five houses and including prior site history, and repeated growth eight apartments, which provide housing for staff, measurements are available for each plantation students and visiting scientists. The Fisher House and many natural stands. A well-developed provides accommodation for approximately 20 network of woods roads provides good access to visiting scientists and students. all areas in the Forest. Fisher Museum houses the Harvard Forest In addition to the three major tracts of Models, twenty-three dioramas portraying the land in Petersham (Prospect Hill, Tom Swamp history, ecology and management of central New and Slab City tracts), the Harvard Forest owns England forests. The Gould Audio Visual Center two smaller parcels in Petersham, the 28-ha Tall and lecture hall with seating for one hundred Timbers tract in Royalston, Massachusetts, the persons is also on the first floor. On the second 40-ha Matthews tract in Hamilton, Massachusetts floor are exhibits related to forest ecology: root and the 10-ha Pisgah tract in Winchester, New biology, soil science, plant/pathogen interactions, Hampshire. The Pisgah tract, an old-growth stand the effects of disturbance on vegetation, and the blown down in the 1938 hurricane, is part of the local history of land-use in Petersham. 5000-ha Pisgah State Forest and is the site of much historical research and an active focus of History of Research and Established Data Bases LTER studies (Foster 1988a). The Harvard Forest has a long and rich The Harvard Forest provides a complete history in the study of forest ecosystems, base for research in forest, ecosystem and vegetation history, and development (Whitney historical ecology and biosphere-atmosphere 1989; see "Publications of the Harvard Forest interactions. In the past decade, the Forest has LTER," this volume). This research background overseen phenomenal growth in scientists, provides baseline data for current studies at the educators, students, collaborators, research and Harvard Forest. education programs, and laboratory, computing, Beginning in 1907 studies at the Forest archival, teaching and housing facilities. focussed on silviculture and forest production Shaler Hall contains offices, seminar including mineral nutrition (Spaeth 1922, Mitchell rooms, a 23,000 volume library, dining facilities and Chandler 1939) and early breeding for 40, laboratories for paleoecological, tree-ring, experiments. By the 1930s research had expanded

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to include studies of forest nitrogen economy (Gast 1936, 1937), forest dynamics and succession (Fisher 1928, 1933, Griffith et al. 1930), soil morphology, mycorrhizal fungi (Finn 1942) and microclimate (Rasche 1958). S. Spurr increased the local interest in remote sensing, catastrophic disturbance (Spurr 1956b), and micrometeorology (Spurr 1956a), whereas M. B. Davis (1958), H. Raup (1937, 1964) and others (Goodlett 1954, Stephens 1955, Hack and Goodlett 1960) created a strong background in historical ecology and disturbance processes (Stephens 1956, Henry and Swan 1974, Oliver and Stephens 1977, Hibbs 1979, 1982). Within the past 25 years studies have focussed on organism-, community- and ecosystem- level research. Particular strengths have been in tree physiology (Zimmermann 1978, 1983, Holbrook and Zwieniecki 1999), plant development and architecture (Tomlinson 1983, 1987), forest microbiology (Torrey 1978, Tjepkema et al. 1981) and vegetation dynamics (Foster 1988a, 1988b). Research by investigators from the Marine Biological Laboratory Ecosystems Center (Melillo et al. 1983, Melillo and Aber 1984, Nadelhoffer et al. 1986, Steudler et al. 1986), the Woods Hole Research Center (Davidson et al. 2000), and University of New Hampshire (Aber et al. 1983, Aber et al. 1985) have provided a very strong ecosystem component. Integrated research among the many groups using the Forest has contributed to a strong interdisciplinary understanding of forest processes. Data from recent studies and further description of current research themes can be found at the Harvard Forest website: http://harvardforest.fas.harvard.edu/.

16

Literature Cited

Aber, J. D., S. V. Ollinger, C. A. Federer and C. Boose, E. R., D. R. Foster and M. Fluet. 1994. Driscoll. 1997. Modeling nitrogen Hurricane impacts to tropical and temperate saturation in forest ecosystems in response forest landscapes. Ecological Monographs to land use and atmospheric deposition. 64: 369-400. Ecological Modelling 101: 61-78. Compton, J. E. and R. Boone. 2000. Long-term Aber, J. S., S. V. Ollinger, C. A. Federer, P. B. impacts of agriculture on soil carbon and Reich, M. L. Goulden, D. W. Kicklighter, J. nitrogen in New England forests. Ecology M. Melillo and R. G. Lathrop, Jr. 1995. 81: 2314-2330. Predicting the effects of climate change on Compton, J. E., R. D. Boone, G. Motzkin and D. water yield and forest production in the R. Foster. 1998. Soil carbon and nitrogen northeastern U.S. Climate Research 5: 207- in a pine-oak sand plain in central 222. Massachusetts: role of vegetation and land- Aber, J. D., C. Driscoll, C. A. Federer, R. Lathrop, use history. Oecologia 116: 536-542. G. Lovett, J. M. Melillo, P. Steudler and J. Crowley, T. J. 2000. Causes of climate change Vogelmann. 1993. A strategy for the over the past 1000 years. Science regional analysis of the effects of physical 289(5477): 270-277. and chemical climate change on biogeo- Davidson, E. A., S. E. Trumbore and R. graphical cycles in northeastern (U.S.) Amundson. 2000. Biogeochemistry: soil forests. Ecological Modelling 67: 37-47. warming and organic carbon content. Aber, J. D., J. M. Melillo, K. J. Nadelhoffer, C. Nature 408: 789-790. McClaugherty and J. Pastor. 1985. Fine Davis, M. B. 1958. Three pollen diagrams from root turnover in forest ecosystems in central Massachusetts. American Journal of relation to quantity and form of nitrogen Science. 256: 540-570. availability: a comparison of two methods. Finn, R. R. 1942. Mycorrhizal inoculation of soil Oecologia 66: 317-321. of low fertility. Black Rock Forest Paper Aber, J. D., J. M. Melillo, C. A. McClaugherty 19: 116-117. and K. N. Eshleman. 1983. Potential sinks Fisher, R. T. 1933. New England forests: for mineralized nitrogen following biological factors. American Geographical disturbance in forest ecosystems. Ecological Society Special Publication 16: 213-223. Bulletin (Stockholm) 35: 179-192. Fisher, R. T. 1928. Soil changes and silviculture Bazzaz, F. A. and S. L. Miao. 1993. on the Harvard Forest. Ecology 9: 6-11. Successional status, seed size and responses Foster, D. R. 1988a. Disturbance history, of tree seedlings to CO2, light, and nutrients. community organization and vegetation Ecology 74: 104-112. dynamics of the old-growth Pisgah Forest, Bazzaz, F. A. S. L. Bassow, G. M. Berntson and southwestern New Hampshire, U.S.A. S. C. Thomas. 1996. Elevated CO2 and Journal of Ecology 76: 105-134. terrestrial vegetation: implications for and Foster, D. R. 1988b. Species and stand response beyond the global carbon budget. Pp. 43-76 of catastrophic wind in central New In: B. Walker and W. Steffen (eds.), Global England, U. S. A. Journal of Ecology 76: Change and Terrestrial Ecosystems. 135-151. Cambridge University Press. Foster, D. R. and E. R. Boose. 1995. Hurricane Boose, E. R., K. E. Chamberlin and D. R., Foster. disturbance regimes in temperate and 2001. Landscape and regional impacts of tropical forest ecosystems. Pp. 305-339 In: hurricanes in New England. Ecological M. Coutts and J. Grace (eds.), Wind and Monogrpahs 71: 27-48. Trees. Cambridge University Press, Cambridge.

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Foster, D. R. and T. M. Zebryk. 1993. Long-term Paper No. 347. U. S. Government Printing vegetation dynamics and disturbance history Office. of a Tsuga-dominated forest in New Hall, B., G. Motzkin, D. R. Foster, M. Syfert and England. Ecology 74: 982-998. J. Burk. 2002. Three hundred years of Foster, D. R., G. Motzkin, B. Slater. 1998. Land- forest and land-use change in use history as long-term broad-scale Massachusetts, USA. Journal of disturbance: regional forest dynamics in Biogeography 29: 1319-1335. central New England. Ecosystems 1: 96- Henry, J. D. and J. M. A. Swan. 1974. 119. Reconstructing forest history from live and Foster, D. R., D. A. Orwig and J. S. McLachlan. dead plant material - an approach to the 1996. Ecological and conservation insights study of forest succession in southwest New from reconstructive studies of temperate Hampshire. Ecology 55: 772-783. old-growth forests. Trends in Ecology and Hibbs, D. E. 1982. White pine in the transition Evolution 11: 419-424. hardwood forest. Canadian Journal of Foster, D. R. , T. Zebryk, P. Schoonmaker and A. Botany 60: 2046-2053. Lezberg. 1992. Post-settlement history of Hibbs, D. E. 1979. The age structure of a striped human land-use and vegetation dynamics of maple population. Canadian Journal of a hemlock woodlot in central New England. Forest Research 9: 504-508. Journal of Ecology 80: 773-786. Holbrook, N. M. and M. A. Zwieniecki. 1999. Fuller, J., D. R. Foster, J. McLachlan and N. Xylem refilling under tension. Do we need Drake. 1998. Impact of human activity and a miracle? Plant Physiology 120: 7-10. environmental change on regional forest Melillo, J. M. and J. D. Aber. 1984. Nutrient composition and dynamics in central New immobilization in decaying litter: an England. Ecosystems 1: 76-95. example of carbon nutrient interactions. Pp. Gast, P. R. 1937. Contrasts between the soil 193-215 In: F. Golley (Ed.), Trends in profiles developed under pines and Ecological Research for the 1980s. Plenum hardwoods. Journal of Forestry 35: 11-16. Press. Gast, P. R. 1936. Studies in the development of Melillo, J. M., J. D. Aber, P. A. Steudler and J. P. conifers in raw humus. III. The growth of Schimel. 1983. Denitrification potentials in Scots pine (Pinus sylvestris) seedlings in pot a successional sequence of northern cultures of different soils under varied hardwood stands. Ecological Bulletin radiation intensities. Statens (Stockholm) 35: 217-228. Skogforsoksanst 29: 582-587. Mitchell, H. L. and R. F. Chandler. 1939. The Goodlett, J. C. 1954. Vegetation adjacent to the nitrogen nutrition and growth of certain border of the Wisconsin drift in Potter deciduous trees of northeastern United County, Pennsylvania. Harvard Forest States. Black Rock Forest Bulletin No. 11, Bulletin No. 28, 128 p. 94 p. Goulden, M. L., J. W. Munger, S.-M. Fan, B. C. Motzkin, G., P. Wilson, D. R. Foster and A. Daube and S. C. Wofsy. 1996. Effects of Allen. 1999. Vegetation patterns in interannual climate variability on the carbon heterogeneous landscapes: the importance dioxide exchange of a temperate deciduous of history and environment. Journal of forest. Science 271: 1576-1578. Vegetation Science 10: 903-920. Griffith, B. G., E. W. Hartwell and T. E. Shaw. Motzkin, G., D. R. Foster, A. Allen, J. Harrod and 1930. The evolution of soils as affected by R. D. Boone. 1996. Controlling site to the old field white pine-mixed hardwood evaluate history: vegetation patterns of a succession in central New England. New England sand plain. Ecological Harvard Forest Bulletin No. 5, 82 p. Mongraphs 66: 345-365. Hack and Goodlett. 1960. Geomorphology and Mulholland, M. 1984. Patterns of change in forest ecology of a mountain region in the prehistoric southern New England, a central Appalachians. Geological Survey regional approach. PhD Thesis, University of Massachusetts, Amherst.

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Mulholland, M. 1988. Territoriality and hort- Massachusetts. Journal of Forestry 20: 117- iculture, a perspective for prehistoric 121. southern New England. Pp. 137-166 In: G. Spurr, S. H. 1956a. Natural restocking of forests P. Nichols (ed.), Holocene Human Ecology following the 1938 hurricane in central New in North-eastern North America. Academic England. Ecology 37: 443-451. Press, NY. Spurr, S. H. 1956b. Stand composition in the Munger, J. W., S. C. Wofsy, P. S. Bakwin, S.-M. Harvard Forest. PhD Thesis, Yale Fan, M. L. Goulden, B. C. Daube and A. H. University, New Haven, CT. Goldstein. 1996. Atmospheric deposition of Stephens, E. P. 1956. The uprotting of trees: a reactive nitrogen oxides and ozone in a forest process. Proceedings of the Soil temperate deciduous forest and a sub-arctic Science Society of America 20: 114-116. woodland. I. Measurements and mechan- Stephens, E. P. 1955. The historical- isms. Journal of Geophysical Research 101: development method of determining forest 12639-12657. trends. PhD Thesis, Harvard University. Nadelhoffer, K. J., J. D. Aber and J. M. Melillo. 228 p. 1986. Fine root production in relation to net Steudler, P. A., J. M. Melillo, E. Ferry, J. Tucker primary production along a nitrogen and A. Turner. 1986. The effect of acid availability gradient in temperate forests: a rain on the emissions of carbonyl sulfide new hypothesis. Ecology 66: 1377-1390. and carbon disulfide emissions from Oliver, C. D. and E. P. Stephens. 1977. European forest soils. EOS (Abstract) 67: Reconstruction of a mixed-species forest in 892. central New England. Ecology 58: 562- Tjepkema, J. D., W. Ormerod and J. G. Torrey. 572. 1981. On vesicle formation and in vitro Ollinger, S. V., J. D. Aber, C. A. Federer, G. M. acetylene reduction (nitrogenase activity) in Lovett and J. M. Ellis. 1995. Modeling Frankia sp. CpII. Canadian Journal of physical and chemical climatic variables Microbiology 27: 815-823. across the northeastern U.S. for a Tomlinson, P. B. 1987. Architecture of tropical geographic information system. U.S.D.A. plants. Annual Reviews of Ecology and U.S. Forest Service Tech. Report NE-191. Systematics 18: 1-21. 30 pp. Tomlinson, P. B. 1983. Tree architecture. Orwig, D. A. 2002. Ecosystem to regional American Scientist 71: 54-57. impacts of introduced pests and pathogens: Torrey, J. J. 1978. Nitrogen fixation by action- historical context, questions and issues. mycete-nodulated angiosperms. BioScience Journal of Biogeography 29: 1471-1474. 28: 586-592. Parshall, T. and D. R. Foster. 2002. Fire on the USDA. 2002. Hemlock Woolly Adelgid Map: New England landscape: regional and 2002. USDA Forest Service GIS Group, temporal variation, cultural and Durham, NH. environmental controls. Journal of Whitney, G. G. 1989. Bibliography of the Biogeography 29: 1305-1317. Harvard Forest, 1907-1989. Harvard Rasche, H. H. 1958. Temperature differences in Forest, Harvard University, Petersham, MA Harvard Forest and their significance. 01366. Harvard Forest Paper No. 4. Zimmermann, M. H. 1983. Xylem structure and Raup, H. M. 1964. Some problems in ecological the ascent of sap. Springer-Verlag: Berlin, theory and their relation to conservation. Heidelberg, New York. Journal of Ecology (Suppl.) 52: 19-28. Zimmermann, M. H. 1978. Hydraulic Raup, H. M. 1937. Recent changes of climate architecture of some diffuse-porous trees. and vegetation in southern New England Canadian Journal of Botany 56: 2286-2295. and adjacent New York. Journal of the Arnold Arboretum 18: 79-117. Spathe, J. N. 1922. Notes on the release of white pine in the Harvard Forest, Petersham,

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Harvard Forest Ecology Symposium 2004 Titles of Abstracts and Presentations (*denotes summer students)

M. Albani and P. Moorcroft. Modeling the Impact of Hemlock Loss on New England Forests with the Ecosystem Demography Model. I. C. Baillie. A Comparison of Methods for the Characterisation of the Edaphic Environments of Some CTFS-Asia Plots in Tropical Rain Forests. A. Barker Plotkin, A. Ellison, J. Butler, D.R. R. Foster and D. Orwig. Establishment of the Hemlock Removal Manipulation Study. A. Barker Plotkin, K. Wilson* and D.R. Foster. Harvard Forest Hurricane Experiment: The Next Generation. M. Battle. Measurement of the O2-CO2 Stoichiometry of Terrestrial Ecosystems. E. Boose, E. Colburn and P. Barten. Hydrological Stations. E. Boose. Information Management. B.H. Braswell, S.C. Hagen, E. Linder, S.V. Ollinger, and A. Richardson. A Statistical Analysis of Tower-Based Estimates of Gross Primary Production. J. Burk, J. Hall, B. Hall, D. Kittredge, D.R. Foster and G. Motzkin. Forest Harvesting in Massachusetts. J.L. Butler, D. Atwater* and A.M. Ellison. Northern Pitcher Plants a Sink for Red Spotted Newts. D. Causey. Seasonal Dynamics and Higher-Order Community Structures of Birds and Their Parasites at Harvard Forest. E. Colburn and H. Jensen-Herrin. Aquatic Macroinvertebrates as Indicators for Biomonitoring Long-Term Change in Lakes and Ponds in the Cape Cod National Seashore. E. Colburn. Salt-Tolerant Midges: Important Considerations for Restoration of a Coastal Wetland in the Cape Cod National Seashore. M.H. Conte and J.C. Weber. Molecular and Isotopic Studies of Biogenic Aerosols and Source Vegetation at the Howland Forest Ameriflux Site. S.D. Costa, J. Brown*, D.A. Orwig and B.L. Parker. A Sampling Plan for Hemlock Woolly Adelgid. P. Crill and R. Varner. High Frequency Measurements of CO2 Efflux from Forest Soil. A.W. D'Amato and D.A. Orwig. The Structure and Composition of Old-Growth Forests in the Berkshire Hills of Western Massachusetts. E.A. Davidson, K. Savage, D. Hollinger and A. Richardson. The Ratio of Soil: Ecosystem Respiration Varies Seasonally at Howland and Harvard Forests. A.M. Ellison, J. Chen*, and M. Lau*, and N. J. Gotelli. Ant Diversity at the Harvard Forest: Preliminary Data from the Prospect Hill and Simes Tracts, with Additional Observations from the Chronic N Addition Plots. E.K. Faison, D.R. Foster, W.W. Oswald, B.C.S. Hansen and E. Doughty. The Post-Glacial History of Hemlock in Massachusetts. D.R. Fitzjarrald, R.K. Sakai, M. Czikowsky, A. Tsoyref and R.M. Staebler. Forest-Atmosphere Exchange Processes: Report on Activities 2003-2004. S. D. Frey, M. Knorr, J. L. Parrent, and R. T. Simpson. Chronic Nitrogen Enrichment Affects the Structure and Function of the Soil Microbial Community. E. Gaige, B. Dail, E. Davidson, D. Hollinger, H. Sievering, M. LeClerc and J. Aber. A Nitrogen Experiment in a Maine Spruce-Hemlock Forest: Results From a Wet NH4NO3 Canopy Fertilization. M. Glessner, B. Dail, E. Davidson, J. Chorover. Factors Affecting Saturability of Nitrate Immobilization in Northern Forest Soils. J. Hadley and P. Kuzeja. Ecosystem Carbon Exchange on Little Prospect Hill.

20 B. Hall, G. Motzkin, and D.R. Foster. Massachusetts’ Woodlands in the Mid-19th Century: Where Were They, What Did They Look Like, and What Are Their Long-Term Legacies. S.S. Jefts and D.A. Orwig. Assessing N Availability Through Multiple Resin Extractions Following the Onset of the Hemlock Woolly Adelgid. J.P. Jenkins, L. Plourde, S.V. Ollinger, M.E. Martin, M-L. Smith, A.D. Richardson, D.Y. Hollinger and B.A. Braswell. Scaling Forest Canopy Carbon Flux From Sites to Landscapes Using Airborne Remote Sensing and Canopy Nitrogen Chemistry. H. Jensen-Herrin, D. Williams, and E.A. Colburn. Salamanders and Benthic Invertebrates in the Headwaters of Bolton Brook, Mount Wachusett, Massachusetts. D. B. Kittredge. Timber Harvest in a Fragmenting Landscape Dominated by a Diversity of Ownerships. D. Köster and R. Pienitz. Environmental history of two New England ponds: natural dynamics versus human impacts. C. Lai, J. Ehleringer, A. Schauer, D. Hollinger, K.T. Paw U, J.W. Munger and S. Wofsy. Photosynthetic 13C Discrimination in North American Temperate Forest Biomes. K.C. Lewis and F.A. Bazzaz. Does Evolutionary Change in Resource Allocation by Alliaria petiolata Drive Invasiveness? M. Lindbladh, E. Faison, D.R. Foster, and W.W. Oswald. The Rise and Fall (and Rise and Fall) of Spruce in Massachusetts. H. Lux, E. Burrows, J.M. Melillo, P.A. Steudler, F.P. Bowles, S. Morrisseau and A. Chan. Soil Warming at Barre Woods: Megaplot Responses after One Year of Warming. A. H. Magill, J. D. Aber, W. Currie, K. J. Nadelhoffer, M. E. Martin, W. H. McDowell, J. M. Melillo and P. Steudler. Ecosystem Response to 15 Years of Chronic Nitrogen Additions. B. Mathewson, E. Colburn and D.R. Foster. Salamanders in Eastern Hemlock Stands – The Forgotten Forest Fauna. P. Medeiros, M.H. Conte, J.C. Weber and B R.T. Simoneit. Sugar Biomarkers as Source Indicators of Biogenic Organic Carbon in Aerosols Collected at the Howland Experimental Forest, Maine. J.M. Melillo, P.A. Steudler, H.B. Lux, E.H. Burrows, J.D. Aber, F.P. Bowles, E. Farnsworth and A. Chan. Soil Warming on Prospect Hill: The First Decade and Beyond (1991-2003). Q. Min. Impacts of Aerosols and Clouds on Forest-Atmosphere Exchange. Q. Min and B. Lin. Satellite Observations of Forest-Atmosphere Exchanges J. E. Mohan, F. A. Bazzaz, E. Burrows, H. Lux and J. M. Melillo. Soil Warming Hastens Successional Dynamics in a Temperate Forest Ecosystem. G. Motzkin, D.R. Foster, D. Kittredge, J. Burk, B. Hall and J. Hall. Twenty Years of Forest Harvesting Across Massachusetts: Influences on Stand Composition and Invasive Plant Species. G. Motzkin, D. A. Orwig, and D.R. Foster. Vegetation and Disturbance History of Ridgetop Pitch Pine and Red Pine Communities in Southern New England. J. O'Keefe. Woody Species Phenology, Prospect Hill Tract, Harvard Forest – 2003. S. Ollinger, M-L. Smith, J. Jenkins, L. Plourde, M. Martin, D. Hollinger and J. Aber. Scaling Forest Productivity Through Space and Time Using Hyperspectral Remote Sensing and Ecosystem Modeling. D. Orwig, P. Del Tredici, H. Lux, R. Schulhof and D.R. Foster. Hemlock Woolly Adelgid at the Arnold Arboretum: Threats and Opportunities. D. Orwig and N. Povak.* Landscape Level Analyses of Hemlock Woolly Adelgid Outbreaks in Massachusetts. D. Orwig, L. Pustell, S. Jefts, and D.R. Foster. Community and Ecosystem Effects of HWA- Induced Logging. D. Orwig, S. Jefts, L. Pustell, and D.R. Foster. Ecosystem Analyses of Hemlock Woolly Adelgid Outbreaks in Southern New England.

21 W.W. Oswald, D.R. Foster, and G. Motzkin. Late Holocene Vegetation Patterns of the Coastal Region of Southern New England and New York. N. Pederson, E. Hammond Pyle, A. Barker Plotkin, G. Jacoby, and S. Wofsy. Contribution of Red Maple to Carbon Uptake in the Eddy-flux Tower Plot Forest. N. Phillips, M. Daley, M. Friedl and G. Salvucci. Vegetation Control of Ecohydrologic Processes. E. Hammond Pyle, C. M. Jones, S. Urbanski, K. McKain*, Z. Liscow*, V.Y. Chow, L. Hutyra, J. Budney, J.W. Munger, and S. Wofsy. Carbon Dynamics at Harvard Forest: Results from the EMS Tower and Ecological Plots. F. Rockwell. Red Maple Re-Visited. L.E. Rustad, I.J. Fernandez, S. McNulty, A. Magill, J.D. Aber, and the NERC N Network. A Cross-Site Study on the Effects of Experimental N Additions on Fine Root Biomass, N Concentration and Total Soil Respiration. K. Savage, E.A. Davidson, and D. Hollinger. Coherence Analysis of High Frequency Soil Respiration, Temperature and Moisture Measurements. N. Scott, E. Davidson, D. Hollinger, C. Rodrigues, J. Lee, H. Hughes, J. Walsh and P. Malerba. Changes in Carbon Storage and Net Carbon Exchange After a Shelterwood Harvest at Howland Forest, Maine. T. Sipe, J. Clowers*, A. Sanchez Sierra*, J. Vuong*. Temporal and Spatial Variation of Nearground Atmospheric CO2 in a Permanent Woodlot Site in Prospect Hill. H. Smith, S.D. Frey, M. Knorr, H. Lux, and J. Melillo. Microbial Responses to Soil Warming. W. Sobczak and E. Colburn. Forecasting Stream Ecosystem Responses to a Regional Landscape Disturbance: Indirect Ecological Consequences of the Removal of Eastern Hemlock from New England Forests. R. Spicer and N.M. Holbrook. Heartwood Formation in Forest Trees: Parenchyma Cell Death as a Driver of Sapwood Senescence. P.A. Steudler, A.K. Chan, J.D. Aber, J. Gulledge, C. Cavanaugh and J.M. Melillo. Long-Term Trends in Soil CH4 Consumption at the Harvard Forest Chronic Nitrogen Addition Experiment: Implications for the Future Growth in Atmospheric CH4. K. A. Stinson and F.A. Bazzaz. Elevated CO2 Allows Smaller Plants to “Catch Up” to Dominants in Competing Stands of Common Ragweed (Ambrosia artemisiifolia). K. A. Stinson. The Impact of Garlic Mustard (Alliaria petiolata) on Native New England Forest Communities and the Importance of Habitat for Controlling its Spread. B. Von Holle, D.R. Foster and G. Motzkin. Historic and Current Influences on Habitat Invasibility in a Mosaic Landscape: Cape Cod National Seashore. K. Wilson*, A. Barker Plotkin and D.R. Foster. Hurricane Damage Exerts Long-Term Effects on Forest Development. X. Xiao, Q. Zhang, B. Braswell, S. Urbanski, S. Boles, S. Wofsy, B. Moore, III and D. Ojima. Satellite-Based Modeling of Gross Primary Production in a Deciduous Broadleaf Forest.

22 CONTRIBUTORS *denotes summer students

Boston University, Boston, Massachusetts Z. Liscow* J.W. Munger M. Daley E. Hammond Pyle M. Friedl S. Urbanski N. Phillips S. Wofsy G. Salvucci

Harvard University Extension School Bowdoin College, Brunswick, Maine Cambridge, Massachusetts

M. Battle B. Mathewson

Colorado State University, Natural Resources Harvard Forest, Harvard University Ecology Laboratory, Fort Collins, Colorado Petersham, Massachusetts

D. Ojima A. Barker Plotkin E. Boose J. Burk Duke University, Department of Biology J.L. Butler Durham, North Carolina E. Colburn A. D’Amato J.L. Parrent E. Doughty A.M. Ellison E. Faison Franklin and Marshall College, Department of D.R. Foster Biology, Lancaster, Pennsylvania J. Hadley B. Hall T. Sipe J. Hall J. Clower* S.S. Jefts A. Sanchez Sierra* H. Jensin-Herrin J. Vuong* P. Kuzeja L. Pustell G. Motzkin Arnold Arboretum, Harvard University J. O’Keefe Jamaica Plain, Massachusetts D.A. Orwig W.W. Oswald P. Del Tredici B. Von Holle

Department of Earth and Planetary Sciences, Museum of Comparative Zoology Harvard University, Cambridge, Massachusetts Harvard University, Cambridge, Massachusetts

J. Budney D. Causey V.Y. Chow L. Hutyra C.M. Jones

23 Department of Organismic and Evolutionary NASA Langley Research Center, Radiation and Biology, Harvard University, Cambridge, Aerosols Branch, Hampton, Virginia Massachusetts B. Lin M. Albani F.A. Bazzaz C. Cavanaugh New England Wild Flower Society N.M. Holbrook Framingham, Massachusetts K.C. Lewis J.E. Mohan E. Farnsworth P. Moorcroft R. Spicer K.A. Stinson Oberlin College, Oberlin, Ohio

J. Chen* Holy Cross College, Worcester, Massachusetts

W. Sobczak Oregon State University, College of Oceanic and Atmospheric Sciences, Corvallis, Oregon

Holyoke Community College P. Medeiros Holyoke, Massachusetts B.R.T. Simoneit

J. Brown* Stockholm University, Department of Geology and Geochemistry, Sweden Humboldt State University, Arcata, California P. Crill M. Lau*

Swedish University of Agricultural Sciences International Paper, Maine Southern Swedish Forest Research Centre Alnarp, Sweden P. Malerba M. Lindbladh

Massachusetts Department of Conservation and Recreation, Division of Forests and Parks The Ecosystems Center, Marine Biological Wachusett Mountain State Reservation Laboratory, Woods Hole, Massachusetts Princeton, Massachusetts E.H. Burrows D. Williams A. K. Chan H.B. Lux J.M. Melillo Mount Holyoke College S. Morrisseau South Hadley, Massachusetts P.A. Steudler J.C. Weber K. McKain*

24 Research Designs, Woods Hole, Massachusetts University of Louisville, Department of Biology Louisville, Kentucky F.P. Bowles J. Gulledge

State University of New York, Atmospheric Sciences Research Center, Albany, New York Université Laval, Paleolimnology-Paleoecology Laboratory, Québec, Canada M. Czikowsky D.R. Fitzjarrald D. Köster Q. Min R. Pienitz R.K. Sakai R.M. Staebler A. Tsoyref University of Maine, Orono, Maine

B. Dail Tree-Ring Laboratory, Lamont-Doherty Earth I.J. Fernandez Observatory and Columbia University E. Gaige Palisades, New York M. Glessner J. Lee G. Jacoby C. Rodrigues N. Pederson J. Walsh K. Wilson

University of Arizona, Tucson, Arizona University of Massachusetts, Amherst J. Chorover P. Barten D.B. Kittredge University of California, Department of Land, Air and Water Resources, Davis, California University of Michigan, Ann Arbor, Michigan K. T. Paw U W. Currie K.J. Nadelhoffer University of Colorado, Denver, Colorado

H. Sievering University of Minnesota, Minneapolis, Minnesota

University of Georgia, Athens, Georgia B. Hansen

M. LeClerc University of New Hampshire, Institute for the Study of Earth, Oceans and Space University of Kansas, Lawrence, Kansas Durham, New Hampshire

D. Atwater* J.D. Aber S. Boles B. Braswell J.P. Jenkins

25 S.C. Hagen L.E. Rustad A.H. Magill S. McNulty M.E. Martin M-L. Smith B. Moore III S.V. Ollinger L.C. Plourde Woods Hole Oceanographic Institution, A. Richardson Department of Marine Chemistry and R. Varner Geochemistry, Woods Hole, Massachusetts X. Xiao Q. Zhang M.H. Conte J.C. Weber

University of New Hampshire, Department of Natural Resources, Durham, New Hampshire Woods Hole Research Center Woods Hole, Massachusetts S. D. Frey M. Knorr E. Davidson W.H. McDowell H. Hughes R. T. Simpson K. Savage H. Smith N. Scott

University of New Hampshire, Mathematics Yale University School of Forestry and Department, Durham, New Hampshire Environmental Studies, New Haven, Connecticut E. Linder F.E. Rockwell

University of Utah, Department of Biology Salt Lake City, Utah Independent Soil and Land Consultant, Bedford England C. Lai J. Ehleringer I.C. Baillie A. Schauer

University of Vermont, Burlington, Vermont

S.D. Costa N.J. Gotelli B. Parker

University of Wisconsin, Madison, Wisconsin

N. Povak*

USDA Forest Service, Durham, New Hampshire

D. Hollinger

26 Modeling the Impact of Hemlock Loss on A Comparison of Methods for the New England Forests with the Ecosystem Characterisation of the Edaphic Demography Model Environments of Some CTFS-Asia Plots in Tropical Rain Forests M. Albani and P. Moorcroft I.C. Baillie The spread of the exotic hemlock woolly adelgid (Adelges tsugae, HWA) across Clarification of the relative the eastern United States is expected to have a contributions from the biotic processes, as substantial impact on New England's forests, encapsulated in the Neutral Theory, and abiotic due to both direct pathogen-induced mortality niche constraints in explaining the complexity of hemlock and by associated pre-emptive and and diversity of tropical forests requires, salvage logging operations. Since eastern amongst other things, the detailed hemlock is a dominant species in several forest characterization of the forests’ edaphic ecosystems, it is expected to cause a cascade of environments. biological, biogeochemical, and physical The Center for Tropical Forest Studies changes in the landscape. In this study, we use has coordinated the establishment of a network the Ecosystem Demography (ED) model, an of large (up to 52 ha) plots at 17 sites individual-based vegetation model describing throughout the tropical lowland forest biome. the growth, reproduction and mortality The data collection on all of these follows strict dynamics of a plant community coupled to guidelines, in order to avoid the methodological biogeochemical models of the associated soil variability that has complicated previous fluxes of carbon, water and nitrogen, to predict attempts at pantropical comparisons and the impact of hemlock losses on the structure syntheses. and function of New England forest Until recently there was a considerable ecosystems. The effects of HWA infestation are mismatch in the data for the CTFS plot between incorporated into ED as an additional mortality the massive, detailed and dynamic term on hemlock, which increases from 0 to characterization of the biotic components of the 90% over a period of approximately ten years ecosystems and the generalized categorization from the first arrival of the infestation. of their physical environments. This will be Simulations of the model at Harvard Forest remedied substantially by the recently show that, even in mixed forests where developed protocol for the standardized hemlock biomass represents around only 10% sampling and analysis of the soils of CTFS of the above ground biomass, the onset of plots. Because of the problems of inter-lab hemlock mortality causes an immediate decline variation, the Protocol stipulates that the soils in Net Ecosystem Productivity (NEP Fig. 1). At can be described and extracted in-country but the peak of infestation, NEP is reduced by 35% that the extracts are all assayed in a single compared to non-infested stands, and is still laboratory, at Cornell University. 25% lower 20 years after initial infection. The This study examines two aspects of the long-term impact on the carbon cycle is due to Protocol’s choice of methods. Firstly, only the the replacement of hemlock by hardwoods that top 10 cm is sampled. This is the zone of have higher rates of biomass turnover. We are highest nutrient uptake by root and mycorrhizal now modeling forest dynamics at 0.5-degree systems. However, it is also the zone of highest resolution for the whole of New England, to temporal and spatial variability in nutrient examine HWA impact on regional carbon contents. The second is the choice of the fluxes. These regional simulations incorporate Mehlich III solution as the extractant. This is a the historical expansion of the HWA as moderate extractant, and removes higher recorded at the county level by the US Forest quantities of P, and probably also of the main Service, and its projected expansion in the next nutrient cations, than the neutral salts or weak 50 years. acid extractants used for conventional determinations of available P and exchangeable

27

Figure 1. ED simulation of the impact of hemlock woolly adelgid infestation on the annual Net Ecosystem Productivity (NEP) of a mixed hardwood forest (10% hemlock by aboveground biomass) on medium soils in central Massachusetts.

M. Albani and P. Moorcroft cations. However it is not as powerful as the The forthcoming data will facilitate the concentrated mineral acids, which extract comparison of results obtained by different reserve or total contents. analytical techniques. In particular it will enable The soils of the 52 ha CTFS at the older data to be compared with those obtained Lambir National Park in Sarawak, Malaysian under the new Protocol. The site Borneo were surveyed in November-December characterizations obtained by the different 2003 with respect to pedological features, analyses will be compared with the botanical topography and parent material lithology, and zonations of the plots. It is anticipated that no assigned to soil series in the Sarawak Soil single method will be wholly effective in Classification. They were sampled at 60 elucidating edaphic effects on forest. Rather stratified random points, for both topsoil (0-10 results indicating apparent effects will need to cm) and subsoil (45-55 cm). The 120 samples be integrated. The data from topsoils and the have been thoroughly mixed and subdivided. weaker extracts are better indicators of the pool One portion of each is being analyzed in of nutrients in circulation through the Sarawak by their standard available and reserve vegetation-litter-topsoil organic matter. Data nutrient methods. The other portion has been from subsoils and stronger acid-based extracted with Mehlich III and the extracts are extractants better indicate the size of the currently being assayed at Cornell. nutrient reserves in the mineral components that I am currently in Thailand and about to may be available to top up the biotic cycle. visit the Huai Khae Keng CTFS plot. The soils During the fieldwork on CTFS plots in there will be surveyed as at Lambir, and Sarawak, Thailand and Sri Lanka, I am possibly also sampled, depending on time and conducting a subsidiary study of the occurrence resources available. and importance of throughflow in different

28 tropical forest systems. At Lambir a composition of post-hemlock forest). In 2005, preliminary attempt at measurement was treatments will be implemented on the entire destroyed by the intensity of the throughflow. 90m by 90m plot. The interior 30m by 30m is Different methods of measurement are being the focus of intensive measurements, whereas considered. For the present qualitative the surrounding 30m will act as a buffer. We observations continue. are currently working to measure diameters, tag and map all the trees greater than 5 cm diameter Establishment of the Hemlock Removal in the plots. Results from the core 30m by 30m Manipulation Study area of each plot confirm that hemlock dominates basal area and stem numbers in all A. Barker Plotkin, A. Ellison, J. Butler, D.R. hemlock plots, and hardwoods dominate the Foster, and D.A. Orwig two hardwood control plots (Table 1). Basal area and stem density are within the observed Hemlock decline in New England is range for these forest types. Black birch is caused by direct and indirect effects of invasion common in the two hardwood control plots, of the hemlock woolly adelgid. Direct damage which dominates many sites after hemlock from the insect is causing gradual mortality of mortality (Orwig and Foster 1998). hemlock, and widespread harvesting of Numerous collaborators in this study hemlock in advance of mortality creates a have already begun collection of data on the contrasting disturbance. Although both flora (understory vascular plants), fauna (ants processes affect thousands of acres of forest and salamanders), and ecosystem processes annually we have only a limited understanding (soil carbon and nitrogen dynamics) in these of their effects on forest ecosystem function and plots to establish strong baseline information productivity and the nature of the subsequent before treatments are implemented. forest community. We anticipate that harvesting will yield different consequences than gradual Orwig, D. A. and D.R. Foster. 1998. Forest response mortality from the insect. Therefore we have to the introduced hemlock woolly adelgid in designed an experiment to simulate the impact southern New England, USA. Journal of the of both in order to contrast them. To simulate Torrey Botanical Society 125: 60-73. some of the effects of the adelgid (e.g., progressive mortality, retention of the wood on the site) we are girdling all hemlocks in a Harvard Forest Hurricane Experiment: The hemlock-dominated stand. In the adjacent area Next Generation we are conducting a commercial harvesting of hemlock. Results from both experimental A. Barker Plotkin, K. Wilson* and D.R. Foster treatments will be compared to the changes observed in forests that are being infested by The hurricane experiment at Harvard the adelgid, and can also be included in Forest was designed to simulate the impacts of integrated analyses of a suite of large a catastrophic storm like the 1938 New England experiments that form a core component of the Hurricane to mature red oak – red maple forest. Harvard Forest LTER program. In October 1990, canopy trees were pulled over We established eight large (0.8 ha) using a winch, resulting in direct and indirect experimental plots at the Simes Tract of the damage to nearly 70% of the stand. Despite Harvard Forest (Fig. 1). There are two massive structural reorganization, the site replicates of the following treatments: hemlock maintained biogeochemical function and girdling (to simulate many of the effects of resisted major change in understory species HWA), hemlock commercial logging (to composition. This contrasts with the more simulate the preemptive logging that is dramatic changes seen after the 1938 hurricane, occurring in hemlock forests in our region), where hurricane effects were conditioned by a hemlock control (no treatment), and hardwood landscape dominated by old-field white pine, control (representing a possible future and the region-wide salvage logging that

29

Figure 1. Map of the Simes Tract of Harvard Forest, showing locations of the hemlock manipulation plots (plots 1 – 6) and hardwood control plots (plots 7 and 8). Plots are 90m by 90m; treatments (girdling and logging) 6 are planned for 2005. 5 4 1 3 2

8

Table 1. Percent basal area by species and total basal area (m2/ha) and stem density (number of trees/ha) for the core 30m by 30m area of the eight hemlock removal manipulation plots at the Simes Tract of Harvard Forest. Survey of overstory trees in the buffer area of these plots continues. Other species include yellow and paper birches, sugar maple, black oak, white ash, hickories, black cherry, and hophornbeam.

Plot Hemlock White Red Red White Black Other Total Total pine maple oak oak birch Basal Stem Area Density 1: hemlock 82 13 21201 49.6889 2: hemlock 68 10 2 20 0 1 0 44.2 1011 3: hemlock 56 16 8 9 10 0 1 40.5 822 4: hemlock 77 0 3 2 0 19 0 51.4 1200 5: hemlock 78 0 86161 52.2856 6: hemlock 70 9 115023 71.9633 7: hardwood 6 36 9 13 0 24 12 44.8 1222 8: hardwood 0 0 14 33 0 45 8 26.4 1144

A. Barker Plotkin, A.M. Ellison, et al.

30 followed this hurricane (Foster et al. 2004). peak and competition begins to eliminate many One goal of the experiment is to study of the trees. regeneration mechanisms and changes in tree species composition. In summers 2000 and Cooper-Ellis, S. M., D.R. Foster, G. Carlton and A. 2003, we surveyed all stems that had grown Lezberg. 1999. Forest response to catastrophic above 5 cm dbh (diameter at breast height) wind: results from an experimental hurricane. across the experimental and control sites. Ecology 80: 2683-2696. These new recruits to the stand represent the Foster, D.R., S. Cooper-Ellis, A. Barker Plotkin, G. Carlton, R. Bowden, A. Magill and J. Aber. most vigorous fraction of the total regeneration 2004. Simulating a catastrophic hurricane. at the site, and suggest how the future Pages 235-258 in Foster, D.R. and J. D. Aber composition of the forest will differ from the (eds.). Forests in Time: The Environmental pre-manipulation stand. Consequences of 1,000 Years of Change in New Between 2000 and 2003, the number England. Yale University Press, New Haven, and basal area of new stems >5 cm dbh CT. increased greatly in the experimental site (Table Oliver, C.D. and B.C. Larson. 1996. Forest Stand 1). These trends suggest that the stand is still in Dynamics (Update Edition). John Wiley & the stand initiation phase of development Sons, New York. (Oliver and Larson 1996), although observed mortality of saplings in the site suggests that Measurement of the O -CO Stoichiometry competitive thinning of the stand is occurring 2 2 of Terrestrial Ecosystems simultaneously. In the unmanipulated control site, stem density and basal area also increased M. Battle between 2000 and 2003, but the total amount of recruitment remains very low. We are presently constructing an After the hurricane manipulation, instrument to simultaneously measure O and vigorous sprouting of damaged trees helped to 2 CO in situ in ambient air. The instrument stabilize the site (Cooper-Ellis et al. 1999). 2 (based on a design of Stephens et al. [2001]), However, most of the stems that have grown will be installed at the Environmental above 5 cm dbh are saplings (mostly seedlings Measurement Site at Harvard Forest. Air will that were present in the understory before the be drawn from two heights: one near the ground manipulation, plus some trees that regenerated and another near the top of the canopy. With from seed following the manipulation), whereas active pressure and flow control, and sprouts comprise less than 20% of the recruits. appropriate standard tanks, we expect to Species composition remained stable achieve a precision of ~1.5 per meg (0.0015 between 2000 and 2003. The new cohort in the permil) for O and 0.08ppm for CO for a 6- manipulation is dominated by black birch 2 2 minute measurement. O and CO (Betula lenta), followed by red maple (Acer 2 2 measurements will be tied to the Scripps and rubrum) and yellow birch (Betula WMO scales through a suite of 4 high-pressure alleghaniensis) (Fig. 1). Early successional standard tanks. A schematic diagram of the species such as paper birch (Betula papyrifera) equipment is shown in Fig. 1. We expect to and pin cherry (Prunus pensylvanica) form a install the instrument at the EMS in the summer relatively minor component of the new cohort, of 2004. and are mostly found on localized areas of soil Simultaneous measurements of O and disturbance such as tip-up mounds. Red oak 2 CO in ambient air characterize the (Quercus rubra) was a dominant species in the 2 stoichiometry of carbon storage and release at pre-manipulation forest, but only three red oaks the ecosystem scale. This stoichiometry have grown into the 5 cm size class since 1990. (hereafter α) is of interest for two reasons: We will continue to monitor this new cohort, and expect that species composition may 1. α is essential for inferring carbon fluxes change once stem numbers of the new cohort from measurements of atmospheric O2

31

Table 1. Stem numbers and basal area of new stems >5 cm dbh in the Harvard Forest hurricane experiment and control plots ten and thirteen years after the manipulation.

Year Hurricane Experiment Plot Control Plot Stems per hectare Basal area (m2/ha) Stems per hectare Basal area (m2/ha) 2000 630 2.45 27 0.07 2003 902 4.05 50 0.13

450 400 Recruitment in Hurricane Pulldown 350 2000 300 2003 250 200

Stems/hectare 150 100 50 0

h h h r rc c ple ne rry irch ir ries Pi B B Ma o d Oak Othe k r Beec e e ow bi e ick it n Che lac ll H h i R B e Red W lack CherryP Y Pap B

Figure 1. Species composition of new stems (>5 cm dbh) in the hurricane experiment. Overall numbers increased, but species composition remained stable between 2000 and 2003.

A. Barker Plotkin, et al.

32

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(see e.g. Keeling and Shertz [1992]). synthesized and respired, and the This is because terrestrial source of nitrogen in the system photosynthesis stores carbon and (ammonium vs. nitrate). releases O2 in the molar ratio α. Thus, [Severinghaus, 1995]. measurements of O2 are useful for determining carbon fluxes only if α is Keeling, R.F. and Shertz, S.R. (1992). Seasonal and independently known. To date, α has interannual variations in atmospheric oxygen been directly measured for only one and implications for the global carbon cycle. ecosystem [Stephens, 2001], yet we Nature, 358:723-727. expect α to vary from one ecosystem to Severinghaus, J.P. (1995). Studies of the Terrestrial the next. All global estimates of α are O2 and Carbon Cycles in Sand Dune Gases and in Biosphere 2. PhD thesis, Columbia indirect [Severinghaus, 1995]. University. 2. The value of α, and its temporal Stephens, B., Bakwin, P., Tans, P., and Teclaw, R. behavior, will provide insight into the (2001). Measurements of atmospheric O2 cycling of nutrients in the forest. This variations at the WLEF tall-tower site. Poster th is the case because we expect α to presentation. 6 International CO2 conference, depend upon whether respiration is Sendai Japan. heterotrophic or autotrophic, the nitrogen content of the biomass being

33 Hydrological Stations personnel (investigators and contact person), temporal coverage (start and end dates), E. Boose, E. Colburn and P. Barten geographical coverage (location description, latitude, longitude, elevation), taxonomic Plans to begin long-term hydrological coverage (species, genera, etc. studied), measurements on two small headwater streams keywords, abstract, methods, and related in the Prospect Hill Tract at the Harvard Forest datasets. were further developed over the past year 3. The updated metadata was encoded through the following activities: into EML (Ecological Metadata Language), an 1. A survey of all Harvard Forest application of XML (Extensible Markup researchers was conducted to identify research Language) developed for use by ecologists and questions that might be advanced by adopted by the LTER Network as its standard hydrological measurements, and to solicit for scientific metadata (for details see recommendations on locations and methods for http://ecoinformatics.org). EML provides a such measurements. highly structured format that can be read and 2. A draft plan was created for the interpreted directly by computer (interested deployment of weirs and wells in the Nelson Windows users can view EML files in Internet and Bigelow Brook watersheds, based on the Explorer). Implementation of EML across the results of the survey and on field inspection of LTER Network and beyond is expected to potential sites. This plan will be finalized in greatly enhance the ability to locate, interpret, spring 2004, with deployment to begin in and integrate scientific datasets. summer and fall 2004. 4. The Data Archive was redesigned to 3. The Fisher Meteorological Station include an Overview page, Data page, and link (http://harvardforest.fas.harvard.edu/hfmet) was to EML file for each dataset. Overview pages upgraded with new sensors to measure contain discovery-level metadata and are photosynthetically active radiation (PAR) and produced directly from EML files using a net radiation (short and long wave). These translation program written in XSL (Extensible measurements will complement planned Stylesheet Language). Data pages contain hydrological measurements and provide entity-level metadata (information on individual essential data for hydrological modeling. tables and variables) and links to data files, and for the most part are still encoded in html by hand. Information Management 5. Entity-level EML files were completed for two datasets (HF000 and E. Boose HF001). Data pages for these datasets were created directly from EML files using a second The Harvard Forest Data Archive XSL translation program. Completion of (http://harvardforest.fas.harvard.edu/data/archiv entity-level EML for other datasets in the Data e.html) contains data and metadata Archive is a goal for the coming year. (documentation) for research projects based at the Forest. Several improvements were implemented over the past year: A Statistical Analysis of Tower-Based 1. The number of datasets in the Estimates of Gross Primary Production Archive was nearly doubled (from 63 to 105), primarily through the addition of recent B.H. Braswell, S.C. Hagen, E. Linder, S.V. datasets. Ollinger and A. Richardson 2. Discovery-level metadata for each dataset was updated using survey forms filled Time series of gross ecosystem CO2 out by individual researchers. This information, uptake, with associated uncertainty estimates, is which enables “discovery” of appropriate desirable for detailed evaluation of process and datasets from a catalog, includes project title, satellite-based models of canopy

34 photosynthesis. Furthermore, the models F = R(Tair, Tsoil) - P(Tair, PAR, VPD). (2) operate on a variety of time scales, so one needs a way to provide error accounting for the time This second formulation may be integrated gross fluxes (e.g., daily, monthly, desirable because it does not assume respiration and annually). Gross photosynthesis (P) is controls are the same in the day as they are at generally estimated as the difference between night, but it conversely does not easily allow for statistically modeled respiration (R) and net separation of errors in P and R during the day. ecosystem exchange (F). The relatively large Thus in this presentation we focus on the number of data gaps (>40%) also requires sequential approach (Equation 1). statistical predictions for gap filling during the Unfortunately, ordinary multiple-linear or day, so that nonlinear regression is problematic using eddy flux data because of (1) strong ⎧0 Night ⎫ heteroscedasticity (e.g., Fig. 1), which indicates ⎪ ˆ ⎪ that the uncertainty should be a function of P = ⎨R − F Day, No Gap⎬ , (1) temperature or other variables; and (2) ⎪ ˆ ⎪ ⎩P Day, Gap ⎭ autocorrelation of the prediction errors, which indicates that accumulated error for time- where R-hat and P-hat are estimates based on integrated fluxes will be inaccurate. Confidence climate, time of year, time of day, and/or other intervals for time-integrated fluxes should not covariates. Alternatively, F=R+P can be be estimated by Monte-Carlo simulation based estimated using all the valid NEE data, based upon 2-σ variations in fitted parameters, upon an ecosystem process oriented model that because the resulting distributions are prescribes the functional forms, and thus the associated with the mean response, not the separate roles of P and R, for example, variance of the observations, which is often much smaller. We combined weighted least

Figure 1. Nighttime NEE and modeled respiration as a regression fit based on temperature only. If temperature is used to model respiration, then the uncertainty (prediction standard deviation) for each daytime estimate should be a function of temperature. A weighted least squares transformation of the data results in confidence intervals that adequately represent this uncertainty.

B.H. Braswell, et al.

35 squares and ARIMA modeling to resolve these We are currently in the process of problems, resulting in estimates of gross checking for errors and discrepancies in the ecosystem uptake of CO2 and error estimates, at maps and databases, based on a small sample (5 various time scales. percent) of the plans entered to date. During the coming year plans from 2002 and 2003 will be added, which will give us 20 years of data. Forest Harvesting in Massachusetts Information from the project has already been used as part of the hemlock woolly adelgid J. Burk, J. Hall, B. Hall, D. Kittredge, D.R. study, and will be used for a major study of Foster and G. Motzkin invasive plant dynamics in Massachusetts.

Since mid-2001 we have been mapping and recording data for timber harvesting Northern Pitcher Plants a Sink for Red throughout Massachusetts for the period 1984 Spotted Newts to 2001,. This is an expansion of the pilot North Quabbin study, based on Chapter 132 Forest J.L. Butler, D. Atwater* and A.M. Ellison Cutting Plan files maintained by the state Department of Conservation and Recreation The northern pitcher plant (Sarracenia (formerly Department of Environmental purpurea) receives much of its nutrients from Management) foresters and filed at six regional the decomposition of prey by the food web that offices. inhabits its pitcher-shaped leaves. With the Preliminary analysis, including data exception of a rare frog or lizard, the captured from the pilot study, indicates that over 470,000 prey consists predominantly of ants, beetles, acres were harvested during this time, with an spiders, and slugs. In the summer of 2003, we average of 38 acres per operation; the largest recorded an unusual occurrence of 22 red- individual cut was 900 acres. Totals of spotted newts (Notophthalmus viridescens approximately 976,000 million board feet and viridescens) captured by northern pitcher plants 786,000 cords were reported harvested. Stand during our nutrient manipulation experiment at types, harvest objectives, and species data were Tom Swamp (Fig. 1). Newts were found also recorded for every plan. among the larger of our experimental plants but Seventy-eight percent of the 12,200 were not associated with any particular harvests filed during this time were conducted nutrient-addition treatment. This observation by private landowners, while the state suggests that capture of amphibian prey by Metropolitan District Commission and northern pitcher plants might not be as rare an Department of Environmental Management event as previously believed. accounted for 7 and 3 percent respectively. The Our observations provide insights into remaining 12 percent was divided among local both the behavior and population dynamics of public agencies, nonprofit organizations, red-spotted newts and the nutrient dynamics of sawmill operators, and the Army Corps of northern pitcher plants. Newts were found Engineers. Harvest density was generally during the months of August and September, a consistent from the Berkshires to the I-495 time when they are preparing to undergo region, with notably heavy activity in the metamorphosis into terrestrial red efts. The Westfield River and North Quabbin areas; there sequences of events that led newts to enter was a significant decrease east of 495 with pitcher plants and subsequently die are not many towns not reporting any cutting during clear. However, it is possible that while in this time. Data was close to complete for the search of a place to undergo metamorphosis, state for the time period, with the only missing newts were attracted to pitcher plants while also information being several years from the North in search of food or a place to avoid predation. Shore region. Once trapped within the pitchers, newt mortality might have been caused by

36 intolerance to the low pH of the pitcher water or though the area of active outbreaks has moved a result of bacterial or autolytic enzyme attack. westward, general monitoring and surveillance As a consequence, newts became a source of activities on WNV prevalence indicates that the prey for the pitcher plant and its associated virus is still prevalent within the Northeast. inquiline community. This project is focused on understanding the Compared to prey typically caught by ecological and evolutionary patterns of pitcher plants in Massachusetts, which is prevalence in avian viruses and parasites, generally one to five ants each day, one newt including naturally occurring viruses like represents a much more substantial source of Newcastle Disease Virus (NDV) and Influenza nitrogen. In particular, the amount of nitrogen A, and emergent diseases like WNV. In this in the biomass of one larval newt (5 mg N) is initial phase of the work, I am studying the over 100 times greater than the total nitrogen in relative roles of migrant species, which may act a single ant (0.042 mg N). Furthermore, one as long-distance vectors, and resident species, newt contains (supplies) an amount of nitrogen which may act as amplifying hosts and equivalent to the total nitrogen found within an reservoirs for disease organisms. To this end, it entire pitcher. Although the ecological is particularly important to be able to quantify implications of our observations require further the seasonal dynamics and interactions among study, these findings suggest that the capture of residents and migrants to provide a context for newts by northern pitcher plants may represent temporal and spatial variability of prevalence in a significant source of nitrogen previously viruses and other parasites. overlooked in pitcher plant nutrient dynamics. We have been conducting a census of birds at three tracts at Harvard Forest (Symms, Tom Swamp, Prospect Hill) by sight, sound, and mist-netting at roughly two-week intervals since May, 2003. Mist-netted birds additionally are being sampled by cloacal swab for subsequent analysis designed to detect the presence of viral RNA and DNA; birds are released after capture. Laboratory work is ongoing, but intensive study has been delayed until the renovation and construction of lab space at the MCZ. The most complete results to date relate to observations of the seasonal dynamics and community structure within the avifauna. Figure 1. A red-spotted newt (Notophthalmus Observational data includes presence viridescens viridescens) larva captured by and and numbers of positively identified birds, drowned in a pitcher plant (Sarracenia purpurea). habitats and site characteristics, exact localities (determined by GPS), and behavior. Sight, sound, and netting data were converted into Seasonal Dynamics and Higher-Order absolute abundances using Distance 4.1, a Community Structures of Birds and Their software program designed to convert census Parasites at Harvard Forest data into densities and trajectories. From these data, community structure was visualized as D. Causey social networks using UCINET and PAJEK, and modeled by log-linear multiway The emergence of West Nile Disease contingency analysis. An example is shown Virus (WNV) in North America in 1999 had an below, where the interactions among the 30 immediate and devastating impact on bird commonest species found in four contigous communities in the Northeastern US. Even habitats (disturbed, secondary growth, pine forest, and meadow) are indicated by a 3-D

37 multi-digraph of associations. In early summer, Salt-Tolerant Midges: Important 21 species are closely associated by incidence Considerations for Restoration of a Coastal spanning forest-meadow habitats; five species Wetland in the Cape Cod National Seashore. (e.g, Dark-eyed Junco [J hyem]alis) range widely but interact only with a few select E. Colburn species (e.g., Chipping Sparrow [S pass]erina). These peripheral members of the community Attempts by the National Park Service are hypothesized to act as bridging vectors of to restore tidal flow to East Harbor, a tidally disease pathogens in migrant and casual visitors restricted lagoon in the Cape Cod National into the core community of residents. Seashore, Truro, MA, have been hampered by a variety of interacting physical, biological, and sociological variables. Among these is the presence in the lagoon of high densities of larval aquatic midges, Chironomus decorus. When the adult midges emerge, they form dense clouds of insects, clouding screens, darkening the sky, fouling paint on vehicles and buildings, and piling up in reeking windrows as they decay. Nuisance emergences occur only sporadically, and the most recent of these coincided with a number of actions taken by the Park Service to begin restoring tidal flow to the lagoon. To address concerns that tidal restoration might exacerbate the midge problem, we carried out laboratory studies of salinity tolerance in the midge larvae. Our Aquatic Macroinvertebrates as Indicators results show that in cold water, larvae tolerate for Biomonitoring Long-Term Change in all but very high (35 ppt) or very low (0 ppt) Lakes and Ponds in the Cape Cod National salinities. At temperatures allowing larval Seashore. growth, most larvae complete development at salinities up to 7 ppt, and some individuals can E. Colburn and H. Jensen-Herrin develop successfully at salinities as high as 17.5 ppt. If projected levels of tidal exchange are Over the past year we continued to met in the lagoon, it seems probable that future collect aquatic macroinvertebrates from flooded nuisance emergences of C. decorus will be vernal pools and from deepwater and shoreline avoided. habitats in kettle ponds on Cape Cod. Processing of the samples is underway. Preliminary multivariate analysis of habitat Molecular and Isotopic Studies of Biogenic variables for the lakes suggested no distinctive Aerosols and Source Vegetation at the groupings based on size, depth, water Howland Forest Ameriflux Site chemistry, trophic status, or geological history. Instead, each water body appears to be unique. M.H. Conte and J.C. Weber It remains to be seen whether aquatic macroinvertebrate assemblages suggest Changes in the concentration and similarities among ponds not elucidated by carbon isotopic composition of atmospheric common limnological data. CO2 can be used to partition the terrestrial and ocean carbon sinks because terrestrial photosynthesis strongly discriminates against 13 C whereas discrimination during ocean uptake is negligible. This approach, though powerful,

38 depends upon the accurate knowledge of the molecular and isotopic composition, although temporal and large spatial scale variation in no clear seasonal trends were apparent. In July terrestrial photosynthesis discrimination (∆), yet 2002 we sampled a smoke plume from forest quantifying ∆ on these scales is a formidable fires in Quebec. The plume contained greatly task due to heterogeneity of terrestrial elevated concentrations of both organic carbon ecosystems. Recently, we have shown (Conte and waxes, and allowed an independent and Weber 2002, Nature 417, 639-641) that the estimate of wax biosynthetic fractionation isotopic composition of higher plant derived relative to fixed carbon in forest biomass (~6.3 leaf wax aerosols can be used to derive direct per mil). Using this estimate, we estimated the estimates of isotopic discrimination of mean ∆ of the wax aerosol “footprint” as 17.7 terrestrial photosynthesis (∆) on large regional per mil. Our estimate closely agrees with space scales and at ~monthly resolution. The model-based estimates of ecosystem ∆ (Lloyd method exploits the specificity of plant and Farquhar) for northern mixed forest biomarkers with the integrating properties of ecosystems, and provides additional evidence atmospheric mixing. that the weighted isotopic composition of plant Our studies at Howland Forest have waxes in the atmosphere reflects the ∆ of the focused upon more closely examining the ecosystem. processes linking photosynthetic isotopic discrimination at the leaf and ecosystem level with the isotopic composition of the integrated A Sampling Plan for Hemlock Woolly plant wax inventory in the atmosphere. The Adelgid specific objectives of our studies are (1) to better constrain the plant wax biosynthetic S. D. Costa, J. Brown*, D. A. Orwig and B. L. fractionation factor (εf) to more accurately Parker convert the leaf wax δ13C signal to an estimate of photosynthetic discrimination, (2) to test the There is a need for a statistically based assumption that the d13C of ablated waxes in sampling plan for detecting and assessing forest boundary layer aerosols accurately tracks populations of hemlock woolly adelgid (HWA), ecosystem ∆, (3) to correlate temporal changes Adelges tsugae. We wanted to establish in waxes with environmental variables and methodology that would allow us to: 1) climatic conditions, and (4) to compare the leaf determine a minimum detection threshold for wax estimates of ∆ with estimates of ecosystem HWA in hemlock dominated forests, 2) define 13 the attributes, such as sample size and type, and discrimination using [CO2] and δ CO2 variations (Keeling plots). the number of samples needed to assess the We measured the molecular and percentage of trees infested, and 3) characterize isotopic composition of waxes in canopy the relationship between the percentage of trees foliage of the major species of the Howland infested in a hemlock stand and the level of ecosystem (hemlock, spruce, red maple, pine, infestation on the trees. Observations were cedar, white birch) and also continuously made in hemlock stands across the Connecticut collected wax aerosols above the canopy over River Valley and Quabbin Reservoir region of the 2001 and 2002 growing seasons (May-Oct). Massachusetts during late spring and early The composition of the wax aerosols indicate summer 2003. The presence/absence of HWA that the northern mixed hardwood ecosystem signs (white woolly masses and/ or their upwind of Howland also contributes to the remains) on 100 trees in each of 17 sites were boundary layer aerosols sampled at Howland, in made at the level of tree, 2 lower branches/tree addition to local conifer forests, and confirms and 5 branchlets/branch. Also, the number of that the “footprint” of the wax aerosols in white woolly masses on each branchlet was boundary layer air masses is of a regional (or recorded so that their population levels could be larger) scale. We also observed temporal and related to the percentage of trees infested – no inter-annual variations in the wax aerosol attempt was made to determine developmental stage, survival status or actual presence of an

39 insect. We choose the white woolly mass variability not captured with a manual style criteria for its ease of determination, campaign. Automated chamber flux systems particularly with the naked eye, which also provide an independent and simultaneous facilitates sampling operations. However, their measurement of nocturnal CO2 efflux, a means use restricts sampling activities to periods when to quantitatively partition one component of the obvious white woolly masses are present. net efflux therefore providing a way to evaluate Our findings suggest that the most and constrain the eddy-flux measurements reliable method for sampling involves made at the EMS tower. examining 2 lower branches per randomly A total of 7299 measurements of soil th selected tree for the presence or absence of CO2 efflux were completed between April 20 white woolly HWA masses (contact S. Costa and November 21st, 2003. The average flux for details). The minimum detection threshold over the moisture gradient for the sampling -2 -1 based on a 75% probability of detecting 1 or period was 2.7 µmoles CO2 m s. The more infested trees within an 100 tree sample of magnitude of soil CO2 efflux varied due to a given site is slightly lower than a 2% temperature and soil moisture content. Daily infestation rate. A binomial model was used to average fluxes correlated well with average relate observed population counts to predicted litter later temperature (Fig. 1). Soil moisture percent trees infested by applying Taylor’s content, measured with ECHO soil moisture Power Law. There was no significant probes, varied significantly over the sampling (alpha=0.05) difference between observed and season but no strong correlations with flux were predicted infestation levels. Based on optimum observed. Collar location along the moisture sampling size analysis, a minimum of 25 and a gradient was qualitatively indicative of soil CO2 maximum of 150 samples are recommended for efflux (Fig. 2). Sampling season averages for characterizing HWA populations down to 10 % the poorly drained, moderately drained and well trees infested with precision=0.25, the standard drained collars were 2.7 ± 0.03, 3.0 ± 0.03, and -2 -1 level used for assessment and management 3.2 ± 0.05 µmoles CO2 m s , respectively. initiatives. Greater precision, as might be required for research purposes, would increase the number of samples needed. Further research 7 is necessary to accumulate additional datasets y = ae(b*x) 6 r2 = 0.69 for validation of the current sampling statistics a = 0.66; b = 0.1

and planned approach to sample collection. -1 5 efflux s 2 -2 4 CO m es an l 3 High Frequency Measurements of CO2

umo 2

Efflux from Forest Soil ily me

Da 1 P. Crill and R. Varner 0 5 101520 We completed automatic chamber Daily mean soil temperature measurements of soil CO2 exchange at the Harvard Forest Environmental Measurement Site (EMS). A fully-automated gas-exchange Figure 1. Daily average efflux of CO2 of all system that multiplexes 8 soil chambers chambers versus litter layer temperature developed for unattended operation at remote field sites was deployed on April 20th, 2003. The frequency (48 fluxes per 24 hours) of the autochamber measurements allow us to capture immediate responses to moisture changes in the soil, the diurnal variation across the season and over a moisture gradient and the interannual

40 canadensis/Picea rubens forests to northern hardwood forests containing mixtures of Acer 6 saccharum, Fagus grandifolia, and Betula -1 s

-2 alleghaniensis. All sites were characterized by m s

e uneven-aged forests with a range of tree sizes 4 ol

m and ages. In addition, the forests contained u , ux l

f sapling thickets of Acer pensylvanicum, Tsuga ef 2 2 canadensis, Fagus grandifolia, and Kalmia

CO Moderately drained Poorly drained latifolia in areas with a recent history of canopy Well drained disturbance. Extensive dendroecological 0 230 235 240 245 analyses of these sites revealed T. canadensis Day of Year ranging from 36.4 to 54.7 cm dbh to be between 289 and 487 years old, while F. grandifolia Figure 2. Daily average CO2 efflux as a function trees were between 150 and 225 years old. of drainage status. Discrepancies in the distribution of age-classes between plots, stands, and topographic P. Crill and R. Varner positions suggest that the disturbance history of these sites has been dominated by small-scale disturbances such as windthrow and may The Structure and Composition of Old- indicate a differential susceptibility to Growth Forests in the Berkshire Hills of disturbance based on forest composition as well Western Massachusetts as topographic and physiographic setting. We will continue to pursue these investigations in A.W. D'Amato and D.A. Orwig additional sites in the Berkshire Hills and the northern and southern Taconic Mountains (Fig. The recent discovery of 28 remnant, 1). old-growth forests in the Berkshire Hills and Taconic Mountains of western Massachusetts has provided an unprecedented opportunity to The Ratio of Soil: Ecosystem Respiration document the composition, structure, dynamics, Varies Seasonally at Howland and Harvard and ecosystem properties of these rare Forests ecosystems. In particular, we are interested in quantifying structural attributes, such as canopy E. A. Davidson, K. Savage, D. Hollinger and A. height, snags, and coarse woody debris (CWD), Richardson the composition of understory plant communities, ecosystem properties, including Partitioning of aboveground and nitrogen retention and nutrient stores, and the belowground respiration is important for stand and landscape-level dendroecological dynamics. understanding their respective responses to We recently documented the forest environmental factors such as temperature, composition and structure of six old-growth day length, drought, and frost. At the stands within the Cold River Gorge in western Howland Forest in Maine, aboveground Massachusetts. This site contains one of the respiration accelerates first in the early highest concentrations of remaining old-growth spring, presumably due to bud break and forests in Massachusetts as well as some of the foliar expansion, which results in soil oldest documented trees in the state. All sites respiration being only 30-40% of total were characterized by extremely steep slopes ecosystem respiration in the early spring (mean = 81.3 %) that ranged in elevation from (Fig. 1b). Soil respiration then gradually 330 to 480 m.a.s.l. Stands were located on increases to about 60-70% of total northern or northwestern slopes and ranged in composition from mixed Tsuga ecosystem respiration during the summer

41 and 90-100% in the autumn and winter. A from the top downward in the spring, and they similar pattern is observed at the Harvard cool from the top downward in the autumn, so forest, except that an apparent mismatch hysteresis based on temperature measured as a between footprints of chamber fixed depth could also be influenced by varying measurements of soil respiration and tower soil depths of CO2 production. During the spring, soil respiration Q10 was always higher measurements of ecosystem respiration than total ecosystem respiration Q10, but the results in unusually low ratios in the winter reverse was observed in the autumn (Table 1). and high ratios in the summer (Fig 2b). In the autumn, both nighttime respiration and Nevertheless, the same pattern of increasing daytime net ecosystem exchange of CO2 drops importance of soil respiration from spring sharply immediately after the first frost and to summer is apparent. The ratio also tends remains low for the rest of the autumn and to drop during summer droughts in both winter. If both photosynthesis and respiration forests, which is consistent with less CO2 drop sharply in response to the first autumn production in the litter layer during drought. frost, the apparent temperature sensitivity of Seasonal hysteresis of Q10s for total ecosystem respiration may be elevated in the ecosystem respiration and soil respiration at the autumn because of this physiological threshold Howland Forest provides an example of effect that induces relatively abrupt dormancy. multiple processes interacting to produce This analysis demonstrates that variable apparent temperature sensitivities. Soil components of total ecosystem respiration do respiration always exhibited a higher Q10 in the not always respond to temperature, moisture, spring than in the autumn (Table 1), perhaps and phenology in synchrony. because of springtime root growth. Soils warm

Figure 1. Location of four old-growth focal areas in western Massachusetts, each containing 3 to 7 old-growth stands. Old-growth overlays are adopted from Leverett and Beluzo, unpublished data. A.W. D'Amato and D.A. Orwig

42

Table 1. Ratio of respiration at 15oC/respiration at 5oC at the Howland forest, Maine, USA. Total ecosystem respiration data are from Hollinger et al. (1999) and Hollinger et al. (submitted). Soil respiration data are from Savage and Davidson (2001) and more recent unpublished data. 1997 1998 1999 2000 2001 2002 All Years Spring Ecosystem Resp 2.8 2.7 3.2 3.9 3.5 2.9 3.1 Soil Resp 4.5 3.0 3.3 5.0 3.9 3.2 3.5 Fall Ecosystem Resp 4.1 3.5 3.2 4.1 3.1 3.1 3.4 Soil Resp 2.8 2.6 3.2 3.0 2.3 1.9 2.5 Soil Resp Spring 4.5 3.0 3.3 5.0 3.9 3.2 3.5 Fall 2.8 2.6 3.2 3.0 2.3 1.9 2.5

Harvard Forest Howland Forest Total RTotal RSoil R Soil RAboveground R 400 600 1997 1998 1999 2000 2001 2002 1996 1997 1998 1999 2000 2001 2002

300500 ux l -1 F ly hr -2 ) ux l 400 eek -1

m 200 F

y C l hr -2 mg ean W

eek 300 M 100 g C m

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0. 5

o 1.2

tal 1.0 0.o 0 Rati T 99 02 98 0.8 00 - - - - -97 t t r-97 r-00 r-01 r-98 y-99 y-02 ly-01 ly-98 l R/ a a p p

0.6 a a eb-99 an-01 an-98 eb-02 ug-99 ug-02 u u ept une-97 une-00 oi

0.4 1-Oc 8-J 4-J S 8-F 4-Nov-01 5-Dec 9-Dec 18-A 14-A 31-Oc 10-M 15-M 12-F 27-A 31-A 27-J 23-J 19-M 23-M 26-S 0.2 18-J 23-J o ( 0.0 Rati 97 00 96 01 - - - Figure 2. (A) Total ecosystem respiration, soil respiration, and aboveground respiration (by difference) at the - Harvard Forest, l-96 l-99 l-02 t t r-96 r-98 r-99 r-02 r-01 y-97 y-00 u u u p a p p a a a eb-97 eb-00 un-98 an-99 ug-97 an-02 ep-98 an-96 un-01 Massachusetts, USA. (B) The ratio of soil respiration:ecosystem respiration; note that the raug-00 tio falls below 0.4 every spring and increases to near 1.0 by the autumn. Soil respiration data are from Savage and Davidson (2001) and more recent unpublished 1-Oc 1-J 5-J 9-J 4-F 9-F 1-Nov-99 5-Nov-02 1-Dec 5-Dec 19-J 24-J 28-J 10-A 15-A 19-A 27-Oc 19-J 23-J 11-M data. Total ecosystem respiration are from Wofsy et al. (http://www.as.harvard.edu/data/nigec-data.ht15-M ml) 23-A 27-S 27-A 15-M 19-M

Figure 1. (A) Total ecosystem respiration, soil respiration, and aboveground respiration (by difference) at the Howland Forest, Maine, USA. (B) The ratio of soil respiration:ecosystem respiration; note that the ratio falls below 0.4 every spring and increases to near 1.0 by the autumn. Data sources are the same as in Table 1.

E.A. Davidson, et al.

43 Harvard Forest Total R Soil R 400 1997 1998 1999 2000 2001 2002

300 ux

l -1 ly F

hr -2 m

eek

200

C mg

ean W M 100

0 ) 2.0

tal R o 1.5

1.0

oil R/T S 0.5 tio (

a 0.0 R 98 00 02 99 - - - - -97 t t r-00 r-01 r-98 r-97 y-02 y-99 ly-01 ly-98 a p p a a a eb-99 an-01 an-98 eb-02 ug-02 ug-99 u u ept une-00 une-97 1-Oc 8-J 4-J 8-F 4-Nov-01 9-Dec 5-Dec 18-A 14-A 31-Oc 15-M 10-M 12-F 31-A 27-A 27-J 23-J 23-M 19-M 26-S 23-J 18-J

Figure 2. (A) Total ecosystem respiration, soil respiration, and aboveground respiration (by difference) at the Harvard Forest, Massachusetts, USA. (B) The ratio of soil respiration:ecosystem respiration; note that the ratio falls below 0.4 every spring and increases to near 1.0 by the autumn. Soil respiration data are from Savage and Davidson (2001) and more recent unpublished data. Total ecosystem respiration are from Wofsy et al. (http://www.as.harvard.edu/data/nigec-data.html)

E. A. Davidson, et al.

Ant Diversity at the Harvard Forest: A horizon of 10-18 inches (25-37 cm) thick in Preliminary Data from the Prospect Hill and as little as 3000 years. Other than Lyford’s Simes Tracts, with Additional Observations detailed work, however, there have been few from the Chronic N Addition Plots. studies of ants at the Harvard Forest. In the summer of 2003, we began an inventory of ant A.M. Ellison, J. Chen*, and M. Lau*, and N.J. species diversity at the Harvard Forest. This Gotelli inventory has three complementary goals. First, we are documenting the taxonomic diversity of In terms of biomass and ecological ants at the Forest and relating this diversity to dominance, ants are the most important vegetation composition, soil characteristics, and invertebrate taxon in terrestrial ecosystems and land-use history. Second, we focus intensively they can alter significantly fundamental on sampling at the Simes Tract to assess processes and dynamics of soil ecosystems. changes in species composition after the large- Over 40 years ago, Walter Lyford suggested (in scale hemlock removal experiment. Third, we Harvard Forest Paper No. 7, 1963) that “the use samples taken from the chronic N addition entire A horizon of some, if not most, virgin plots to test hypotheses that suggest that ant Brown Podzolic soils in New England consists species richness is positively correlated with of material returned by ants to the surface from energy availability (e.g., insolation) or nutrient the B horizon” and that ants could generate an availability and primary productivity.

44 In 2003, we sampled all eight 0.8-ha The Post-Glacial History of Hemlock in experimental plots in the Simes Tract (see Massachusetts abstract by A. Barker Plotkin et al.); all eight chronic N plots; and eight sites scattered E.K. Faison, D.R. Foster, W.W. Oswald, B.C.S. throughout the Prospect Hill Tract (in Hansen, and E. Doughty compartments II, III, VIII, and IX) that represented a range of successional stages and Global climate change and exotic stand types. Each sample consisted of a grid or pathogens are two of the most important threats transect of 25 48-hr pitfall traps and 1-hr cookie to eastern North American forests today, as baits, and 4 L of leaf litter. All sites were well as to forests worldwide. Introduced sampled twice between mid-June and early pathogens have greatly reduced or eliminated August. Stefan Cover at Harvard’s Museum of canopy dominant trees such as elm, chestnut, Comparative Zoology (MCZ) confirmed our and beech on decadal time scales or less identifications of the species. (Castello et al. 1995). Rapid climate change in The current list of 33 species for the the past has caused shifts in vegetation Harvard Forest is given in Table 1. Our survey composition over similar time frames (Post added 22 species to the list published by Mike 2003). Today, eastern hemlock is suffering Kaspari (American Naturalist 161: 459-477, conspicuous declines in southern New England 2003). Old fields and early successional stands from the recently introduced hemlock woolly have the highest number of species, whereas adelgid (HWA) (Orwig 2002). Several studies pine and hemlock stands are least diverse (Fig. show that elevated CO2 levels increase the 1). At the Simes Tract, there were no abundance of phloem-feeding insects differences in species richness or composition (Whittaker et al. 1999), suggesting that current within stand types, although within-plot species atmospheric trends could exacerbate the richness was lower in the hemlock plots (3 ± 1 damage of this pest on hemlock. species per 0.8-ha plot) than in hardwood plots Long-term questions that arise in the (8 ± 1 species per 0.8 ha plot). In the chronic N face of HWA and global warming are: 1. how plots, species richness was higher in the reduced will hemlock become in New England hardwood stands than in the red pine stands, but as a result of this pathogen outbreak; 2. how in contrast to predictions from the literature, ant long will it take hemlock to recover from species richness did not differ among HWA; 3. how will the transition-hardwoods treatments within stands or with difference in forest be altered by hemlock’s decline; and 4. light availability (estimated from hemispherical how will climate change interact with the canopy photographs). current hemlock decline. To address these Hardwood and conifer stands differed questions, we place current conditions into a in species composition (Fig. 2). Non-metric meaningful, long-term context by investigating multidimensional scaling (NMDS) separated the post-glacial record of hemlock in New the hardwood stands from the conifer stands, England. A combination of paleoecological and the mixed stands were more similar to the data -- fossil pollen, charcoal, and % organic conifer stands than to the hardwood stands. The content of sediment cores from lakes spanning a principal reason for this separation is that no broad geographic and environmental gradient in species in the genus Formica were found in the Massachusetts -- historical records (maps, conifer or mixed stands. Note that this documents, and witness tree data), and modern ordination excluded the old-field samples, as vegetation data are employed in this these samples were so different from the forest retrospective. samples that an ordination that included the old- field samples could not separate any of the forest stands from each other. This survey will be extended in 2004 to complete the sampling of compartments and stand types at Prospect Hill.

45 Table 1. Preliminary checklist of ant species for the Harvard Forest.

Ponerinae Myrmicinae *Amblypone pallipes Aphaenogaster rudis *Crematogaster lineolata Formicinae Leptothorax longispinosus *Camponotus nearcticus Myrmecina americana *Camponotus novaboracensis *Myrmica americana Camponotus pennsylvanicus *Myrmica detritinodis *Formica aserva *Myrmica fracticornis *Formica incerta *Myrmica nearctica *Formica lasiodes Myrmica punctiventris Formica neogagates *Myrmica sculptilis Formica subaenescens *Protomognathus americanus *Formica subsericea *Stenamma brevicorne Lasius alienus Stenamma dieckii Lasius nearticus Stenamma impar *Lasius neoniger *Stenamma schmittii Lasius pallitarsus *Solenopsis molesta Lasius umbratus *Tetramorium caespitum

Dolichoderinae *Tapinoma sessile *New records from 2003 survey. Lyford (1963) listed Formica fusca, the name of which is now restricted to a European species. The North American “F. fusca” is F. subaenescens. Nomenclature of Myrmica follows the unpublished work of André Francoeur.

Figure 1. Ant species richness in different stands at the Harvard Forest. PH: Prospect Hill. All plots within stand types of the N-saturation experiment are pooled, as there were no differences in species richness or composition among treatments within stand types. Similarly, all plots within stand types at the Simes Tract are pooled, as there were no differences in species richness or composition within stand types. A. M. Ellison et al.

46

Figure 2. Ordination of the stand types based on ant community composition using non-metric multidimensional scaling. Old-field samples were excluded, as their inclusion led to no separation among the forest stand types. The principal difference between stands is that no species in the genus Formica were found in the conifer or mixed stands.

A.M. Ellison, et al.

Preliminary results show that hemlock declined, and pine fell to its lowest levels in the was present in low numbers in Mass. ~12000 Holocene. cal BP but became established in the region The dramatic, region-wide hemlock ~10,500 cal BP at the end of the Younger Dryas decline at ~5300 cal BP (Fig. 1) was likely Cold period (Fig.1); the species appears to have caused by a pathogen outbreak, although a colonized the region from southeast to concurrent shift to drier conditions may have northwest over the course of 500-1000 years. exacerbated the decline (Newby et al. 2000). Once established, hemlock became more Influx of hemlock pollen decreased by as much abundant in central and western Mass., as is as 95% during this time and did not return to true today. After increasing rapidly, hemlock comparable pre-decline levels for 1000+ years; suffered its first major decline, presumably in in most cases, hemlock never regained its response to a region-wide dry period from former abundance. Oak increased during the 10000-8000cal BP (Newby et al. 2000) that was hemlock decline except in southeastern, Mass., accompanied by higher fire in the eastern half where beech increased dramatically. of Mass. Pine declined with hemlock, and oak About 500-1000 years ago, hemlock and ragweed increased. After ~ 8000 cal BP, began a gradual decline, presumably in moisture levels increased significantly (Newby response to the cooler climate of the Little Ice et al. 2000), and hemlock percentages Age (LIA), while spruce returned in low increased. Beech arrived at this time and numbers. Hemlock’s decline was later increased along with hemlock, while oak exacerbated by the processes of European settlement: land clearance, increased fire,

47 logging for the tanning industry, and intensive Hall, B., G. Motzkin, D.R. Foster, M. Syfert, and J. animal browsing following these disturbances Burk. 2002. Three hundred years of forest and (Rogers 1978). Today, hemlock and other late land use change in Massachusetts, USA. Journal successional species remain less abundant than of Biogeography 29:1319-1335. they were at the time of European settlement, Newby, P.E., P. Killoran, M.R. Waldorf B.N. Shuman, R.S. Webb, and T. Webb. 2000. and in most cases far less abundant than they 14,000 years of sediment, vegetation, and were at 6000 cal BP. Early and mid- water-level changes at the Makepeace Cedar successional species such as birch and red Swamp, Southeastern Massachusetts. maple are more abundant today (Hall et al. Quaternary Research 53:352-368. 2002). Orwig, D.A. 2002. Ecosystem to regional impacts of Hemlock levels have experienced rapid introduced pests and pathogens: historical changes in response to climate change and context, questions and issues. Journal of pathogen disturbances in the past. Recovery Biogeography 29:1471-1474. from major declines has often been lengthy – as Post, E. 2003. Climate-vegetation dynamics in the long as 2000 years. Today’s pathogen-climatic fast lane. Trends in Ecology and Evolution 18:551-553. situation may be similar to conditions of the Rogers, R.S. 1978. Forests dominated by hemlock mid-Holocene hemlock decline and if true, (Tsuga Canadensis): distribution as related to hemlock’s return to pre-HWA numbers may be site and post-settlement history. Canadian centuries in the making. Journal of Botany 56: 843-854. Whittaker, J.B. 1999. Impacts and responses at Castello, J.D., D.J. Leopold, and P.J. Smallidge. population level of herbivorous insects to 1995. Pathogens, patterns, and processes in elevated CO2. European Journal of Entomology forest ecosystems. Bioscience 45:16-24. 96:149-156

Blood Pond, Dudley, MA

d e ck ee c lo ch s w u e k e ch s g pr in em a e ir ra a S P H O B B G R

0 0

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Figure 1. Pollen diagram from south-central Massachusetts depicting 12,000+ years of hemlock dynamics along with coincident changes of other major taxa.. E.K. Faison, et al.

48

Forest-Atmosphere Exchange Processes: the subcanopy sonic anemometer at 8 m, in Report on Activities 2003-2004 addition to recording the tower top turbulent variables as a backup to the Harvard system. D.R. Fitzjarrald, R.K. Sakai, M. Czikowsky, A. We are in the midst of a large ‘turbulence Tsoyref and R.M. Staebler climatology’ project, whose aim is to determine the frequency and intensity of nocturnal mixing We continue our studies of mass and events. This effort is using data from the energy exchanges between the forest and the decade-long time series now available. atmosphere. We place particular emphasis on During this period, the first results from a) understanding how turbulent flux the subcanopy drainage flow project at EMS convergence affects microclimate and b) how was published (Staebler and Fitzjarrald, 2004). local site characteristics may introduce local • Related measurements during the bias into flux observation. In separate Hudson Valley Ambient Meteorology Study climatological studies, we treat spring leaf (HVAMS): Several efforts were made during emergence as a land use “experiment”, to study HVAMS to link NIGEC work at HF with the what changes occur in the environment project. This includes the King-Air overflight accompany leaf emergence. at EMS tower on October 28, 2003. (Fig. 1, Fig. During this period, we pooled some 2) and a series of aircraft profiles (Figs. 3, 4). resources from NIGEC with funding from the A second effort was the establishment of a flux NSF to augment CO2 observations during the tower in the Hudson Valley near Red Hook NY, Hudson Valley Ambient Meteorology Study whose measurements will be continuing for (HVAMS), whose intensive observation period another year at least. A third effort was the occurred during September and October 2003, addition of CO2 measurements to a number of though ongoing measurements continue. The flux-capable weather stations that were EMS tower at Harvard Forest served as a operated during intensive operations from reference site for HVAMS, since the project September-October, 2003. This latter effort is surface measuring stations were not located in aimed to test the viability of operating a large- forested areas. A research aircraft operated scale network of CO2-observing weather during HVAMS and was used to make a series stations across the country (see example, Fig. of comparison passes by the EMS tower in 5). October 2003. At the Symposium, we will briefly discuss our ongoing radiative and Czikowksy, M.J., and D.R. Fitzjarrald, 2004. Long turbulent flux observations but concentrate on term hydrological records contain signals of some interesting details of the fly-by and from seasonal changes in evapotranspiration, submitted to J.Hydromet. the CO2 observation component of HVAMS. •Climatology studies: Our previous Fitzjarrald, D.R.. O.C. Acevedo, and K.E. Moore, 2001. Climatic consequences of leaf studies have showed that leaf emergence along presence in the eastern United States, J. the East Coast can be detected not only by Climate 14, 598-614. analyzing maximum and minimum Staebler, R.M. and D.R. Fitzjarrald, 2004. temperatures (Fitzjarrald et al. 2001), but also Observing subcanopy CO2 advection. Ag. through analysis of runoff properties in the For. Meteor. , in press. same region (Czikowsky and Fitzjarrald 2004). During this period we acquired data for the rest of the continental U. S. and also from Mexico. We are now extending these studies to cover these regions. Flux measurements: •EMS site at Harvard Forest: We continue to operate observations of the radiation suite at tower top at EMS, as well as

49

Figure 1: Trajectory of the King Air flight legs passing over the Harvard Forest EMS tower, October 28, 2003.

Figure 2: King Air time series of Theta and q for the Harvard Forest EMS tower flight legs. Light green vertical lines indicate passage times over the Harvard Forest EMS tower.

D.R. Fitzjarrald, et al.

50

Figure 3: (Left): Profiles of theta and q for the King Air missed approach (descending portion) at Orange, MA Airport, October 28, 2003, 17:42 GMT. (Right): Profiles of O3 and CO2 for the same missed approach, illustrating how the forest was exhibiting little net. uptake in the late autumn.

Figure 4: (Left): Profile of potential temperature and q taken in the Hudson Valley (42.60 N, 73.9 W) on October

8, 2003, 14:16:51 GMT. (Right): Profile of CO2 and O3 .

D.R. Fitzjarrald, et al.

51

Figure 5: (Top): Time series of CO2 and O3 for NCAR PAM stations 2 (Black Horse Farm, Athens, NY) and 3 (Southlands Farm, Rhinebeck, NY), October 31, 2003. CO2 values not yet calibrated, but illustrate the rapid drop as mixing begins in the morning. (Bottom): Network average energy balance components (Rnet, H, LE, and Gsfc) for the 9 NCAR PAM stations deployed in the Hudson Valley for October 31, 2003.

D.R. Fitzjarrald, et al.

Chronic Nitrogen Enrichment Affects the high N (15 g N m-2 y-1) plots in both the Structure and Function of the Soil Microbial hardwood and pine stands at the Chronic Community Nitrogen Amendment Study at Harvard Forest. The samples were analyzed for total and active S.D. Frey, M. Knorr, J.L. Parrent, and R.T. bacterial and fungal biomass, microbial Simpson catabolic response profiles, the activities of cellulolytic and ligninolytic enzymes, and total, We examined how chronic nitrogen (N) labile and microbially-derived organic carbon enrichment of pine and hardwood forest stands (C). Live, fine roots were also collected from has affected the relative abundance, functional the control and low N pine plots and analyzed capacity, and activity of soil bacteria and fungi. for ectomycorrhizal fungal community During Fall 2002 we collected one soil core composition and diversity. Active fungal (5.6 cm diam; organic horizon plus 10 cm of biomass was 27-61% and 42-69% lower in the mineral soil) from each of four 5 x 5 m subplots fertilized compared to control plots in the within the control, low N (5 g N m-2 y-1), and hardwood and pine stands, respectively (Table

52 1). Active bacterial biomass was not greatly season by helicopter, in order to more closely affected by N additions, resulting in mimic naturally occurring atmospheric N significantly lower fungal:bacterial biomass deposition. Within the treatment area, three sub ratios in the N-treated plots. This shift in plots were intensively sampled to determine the microbial community composition was fate of the experimental N. In two sub plots a accompanied by a significant reduction in the 1% 15N label was used to trace ammonium and activity of phenol oxidase, a lignin-degrading nitrate respectively, in foliage, throughfall, soils enzyme produced by white-rot fungi (Fig. 2). and soil water. After three seasons of In the pine stand, ectomycorrhizal fungal fertilization, we determined that approximately community diversity was lower in the low N 40-50% of the experimental N is retained in the treated plot than in the control plot (Table 2). canopy with 10% reaching the forest floor on Differences in ectomycorrhizal community the day of fertilization, approximately 10% lost structure were also detected between control through canopy volatilization and 20-30% and fertilized pine plots, including a reduction washed from the canopy by precipitation in those species with the highest relative events. Ambient precipitation nitrate frequencies in the control community (Fig. 1). constitutes 50-70% of atmospheric N inputs and Finally, N enrichment altered the pattern of approximately 82% of this is retained in the microbial substrate use, with the relative canopy (compared to only 50% retention of + response to the addition of carboxylic acids and ambient NH4 ). However, the experimental carbohydrates being significantly lower in the nitrate appears to have saturated canopy - N treated plots, even after the data were assimilation as NO3 concentrations in + normalized to account for differences in throughfall exceed those for NH4 . Green microbial biomass (Fig. 3). These patterns are foliage 15N contents also show a trend of nitrate consistent with lower decomposition rates and preference in the canopy but this may be + - altered N cycling observed previously at this tempered by transport of NH4 and NO3 to site. other tissues.

Abstract and figures excerpted from Frey, S.D., M. Knorr, J. Parrent, and R.T. Factors Affecting Saturability of Nitrate Simpson. 2004. Chronic nitrogen enrichment Immobilization in Northern Forest Soils affects the structure and function of the soil microbial community in temperate pine and M. Glessner, B. Dail, E. Davidson, J. hardwood forests. Forest Ecology and Chorover Management (in press) Anthropogenic activities have resulted in increased levels of nitrogen deposition to A Nitrogen Experiment in a Maine Spruce- northern temperate forests in recent decades. Hemlock Forest: Results From a Wet These inputs, primarily in the form of NH4NO3 Canopy Fertilization. atmospherically derived ammonium (NH4+) E. Gaige, B. Dail, E. Davidson, D. Hollinger, and nitrate (NO3-), have been the result of H. Sievering, M. LeClerc and J. Aber increased fertilizer use and reliance on fossil fuel. Research has shown that the major sink In response to unanswered questions for these inorganic nitrogen inputs have been about impacts to the carbon (C) cycle by forest soils, which was somewhat increasing anthropogenic nitrogen (N) inputs to ecosystems, we fertilized a 21 ha spruce- hemlock forest canopy in Howland, ME. A 21 ha plot is receiving 18 kg N ha-1 growing season-1 above ambient N input. Liquid NH4NO3 additions occur 5 times per growing

53

Chronic Nitrogen Enrichment Affects the Structure and Function of the Soil Microbial Community

Table 1. Total and active microbial biomass, active fungal:bacterial biomass ratio (F:B) and catabolic evenness for soil collected from hardwood and pine stands at the Chronic Nitrogen Amendment Study at Harvard Foresta

Total microbial biomass Active microbial biomass Catabolic Stand/Plot Fungi Bacteria Fungi Bacteria F:B Evennessb -1 -1 ------µg C g soil------µg CO2-C g soil------Hardwood Control 501 (41) 33 (4.0) 7.5 (0.9) 3.8 (0.4) 2.1 (0.4) 12.59 (1.1) Low N 365 (71) 28 (2.8) 5.5 (0.6) 3.8 (0.3) 1.5 (0.2) 12.15 (0.5) High N 637 (53) 34 (1.7) 2.9 (0.6) 3.2 (0.9) 1.1 (1.6) 8.80 (0.5) Pine Control 407 (60) 24 (0.1) 6.2 (1.5) 1.7 (0.3) 3.7 (0.5) 10.23 (0.9) Low N 406 (50) 24 (1.3) 3.6 (0.5) 1.1 (0.3) 4.1 (0.5) 7.71 (0.9) High N 433 (48) 36 (1.5) 1.9 (0.9) 1.1 (0.1) 1.6 (0.8) 6.85 (0.5) aTotal fungal and bacterial biomass were determined by direct epifluorescent microsopy. Active microbial biomass was estimated by substrate-induced respiration with selective inhibitors. Values represent the mean of four replicates ± one standard error. b 2 Catabolic evenness (E) = 1/Σpi where pi is summed for all substrates and pi = ri/Σri defined as the respiration response of each substrate (ri) as a proportion of total respiration responses summed over all substrates (Σri). The maximum achievable evenness value is 25, the point at which all substrates are used equally. The lower the evenness value, the more variable (i.e., less even) is the respiratory response among the 25 substrates.

S.D. Frey, et al.

54

Table 2. Ectomycorrhizal fungal community diversity for control and low N pine stands. Confidence intervals (CI) for Simpson’s and Shannon’s diversity indices were generated from 1000 bootstrap replicates for each plot. Richness is the total number of observed species per plot. Simpson’s Shannon’s Samples Richness D 95% bootstrap CI H' 95% bootstrap CI Control 119 19 0.90 0.86 – 0.91 2.51 2.26 – 2.57 Low N 33 10 0.75 0.57 – 0.83 1.71 1.25 – 1.98

50

45

40

35 ) (%

y 30 c n e u

q 25 e fr

tive 20 la e R 15

10

5

0

s 2 2 a a 1 s 1 1 u . n 1 . 2 t m . 1 . 1 u . 1 1 . ca p p. i p. ta u p p p. s s c s sp s sp. 2 s lut sp s s la ce a sp. s ogal s a i la la o s sp ll e vo ta sp. e a ve bl u le e n us be sp. 1 a la rm u su cr t ea i ri y e u thei tariu e s s ss ina cri a ta tales n c s ta ani c c c a u u m le le e ta u m o ta ss us lod l R R m ac m a loderm i La el er Bo Bo o xill L A r i Ru ar Pi t lavul d T ma m P t n C o lo Pa De lo c e o o m Pil h t La c ri En To T

Figure 1. Ectomycorrhizal fungal community structure in the pine stand. Solid bars are relative frequencies of EMF species in the control plot; hatched bars are relative frequencies of EMF species in the low N plot.

S.D. Frey, et al.

55 100 A -1

80 Control il C h

o Low N s 60 High N -1 g 40 tivity

ac 20 mol µ 0 Hardwood Pine

100 B -1

80 il C h o s 60 -1 g 40 tivity

ac 20 mol µ 0 Hardwood Pine

Stand

Figure 2. Activity of the cellulolytic enzyme, ß-1,4-glucosidase (A), and the lignin-degrading enzyme, phenol oxidase (B), for soil collected from control, low N, and high N plots in the hardwood and pine stands at the Chronic Nitrogen Amendment Study at Harvard Forest. Each bar represents the mean of four replicates and the error bars are one standard error.

2.0

1.5

1.0 PL

0.5 HC 0.0 HL PC (16% of variation)

-0.5 PC2 HH

-1.0 PH

-1.5 -3 -2 -1 0 1 2 3 4 PC1 (63% of variation)

Figure 3. Principal components analysis of the catabolic response profiles for soil collected from control (C), low N (L), and high N (H) plots in the hardwood (H) and pine (P) stands.

S.D. Frey, et al.

56 surprising in the case of NO3- owing to its determine soluble and insoluble N fractions tendency to be easily leached from soil profiles. using a series of extractions and isotope NO3- rarely accumulates external to living diffusions coupled with solid state isotope ratio organisms in a terrestrial ecosystem because mass spectroscopy. We present results for soil particles are similarly charged and favor 15NO3- additions to mineral soil horizons adsorption of cations (like NH4+) but repulsion under mixed hardwood and red pine plantation of anions (such as NO3-). NO3- entering a sites undergoing the experimental N additions. system as wet or dry deposition should be either (a) quickly assimilated by plants and microbes, (b) microbially converted to an N-containing Ecosystem Carbon Exchange on Little gas (N2O, N2), or (c) leached from the soil. Prospect Hill Theoretically, it should be easy to determine the fate of increased NO3-deposition by measuring J. Hadley and P. Kuzeja inputs, biotic demand and hydrologic N outflows (in most forest ecosystems, gaseous In October 2003 we completed the losses are thought to be minimal). Eventually, second growing season of carbon exchange increased inputs may exceed microbial and measurements using the eddy covariance plant demand and be leached from the system procedure at a site on Little Prospect Hill (Fig. without being utilized; this ecosystem would be 1). Due to surface topography, valid carbon said to have reached a state of “N saturation”. exchange measurements at the site are possible Recent studies have shown, however, that NO3- only with SW, W or NW winds, because winds additions to forest ecosystems are immobilized blowing from the east over the top of Little rapidly and abiotically in some forest soils. Prospect Hill create turbulence patterns Observation that labeled NO3- is reduced incompatible with valid C flux measurements. within minutes of addition to sterilized organic During data analysis in 2003 and early 2004, horizon soils has led to new questions about including reanalysis of 2002 data, we NO3- reactivity and speculation about possible furthermore observed that anomalously large physico-chemical fates for NO3- in soil carbon effluxes appeared to occur with SSW Furthermore, both physico-chemical and winds, specifically between 180 and 215o biological N retention need to be understood in compass direction from the tower. These order to explain the resilience of forests to apparent carbon releases may have also been a additional N deposition. result of turbulence created as air passed over At Harvard Forest in Petersham, slightly higher terrain before reaching the eddy Massachusetts, experimental manipulations covariance tower from the SSW. Fossil fuel have been performed to determine the fate of combustion and agricultural activity near Shaler additional N (as NH4+ and NO3-) in forest Hall and the Fisher House (which are situated at ecosystems. In order to experimentally push a compass bearing of about 200o from the eddy forest ecosystems toward nitrogen saturation, covariance tower) could also have contributed inputs of NH4+ and NO3- have been applied to to the large carbon releases observed in data control, low N, and high N (receiving 0, 50, and from this wind direction. In either case, we 150 Kg N/ha/yr) plots within both pine and concluded that flux measurements with wind hardwood stands. We took soil cores from each from between 180 and 215o could not be used of these plots, divided into mineral and organic in estimates of forest CO2 exchange. layers and exposed them to 15NO3-. With this correction to our data analysis Composite samples were used to determine procedure, the estimate of carbon storage at the initial soil characteristics (dry mass Little Prospect Hill site in 2002 increased equivalence, water holding capacity, initial substantially over our previous estimate. Total inorganic nitrogen quantities, etc.). Following carbon storage at this site for May through the addition of labeled 15NO3 to soil, we took August 2002 was very close to average C subsamples at initiation and after 24 hour storage measured at the EMS site (Fig. 2), incubation. These subsamples were analyzed to

57 although this was followed by lower C storage as a whole. Since 1830 was near the peak of in September and greater C loss in October at agriculture in New England, we have the Little Prospect Hill site relative to EMS. hypothesized that many of the sites that were Relative values at the two sites reversed again wooded at that time probably remained wooded during November and December 2002, and we until the present, resulting in contrasting do not yet have data from the EMS site for vegetation structure and compositon, and 2003. Through the last 8 months of 2002, ecosystem processes than nearby formerly- estimated cumulative net ecosystem exchange cleared sites. This year we have begun an in- (NEE) of carbon was nearly equal for Little depth analysis of this map in an attempt to Prospect Hill and for EMS (Fig. 3). describe more fully what was depicted in 1830 Comparing estimated carbon storage at Little and what those woodlands look like today. In Prospect Hill for the growing seasons of 2002 particular, we are seeking to identify the and 2003, we found that C storage for the first environmental and cultural characteristics that half of the season was lower in 2003, especially best predict the presence of 1830 woodlands for in May and June (Fig. 4), leading to about 1 Mg the different physiographic regions of the state. /ha less carbon stored over the 2003 growing These results will allow us to model forest season compared to 2002. The primary factor locations in towns without 1830 maps and to in this difference was heavy cloud cover in late evaluate the reliability of the map in specific May and early June 2003, which delayed leaf areas. Mid-19th century manuscripts including development and reduced early-season farmers’ diaries and agricultural journals will photosynthesis. be examined to get an overall impression of what the 1830 woodlands may have looked like Barford, C.C., S.C. Wofsy, M.L .Goulden, J.W. in terms of structure and composition and how Munger, E.H. Pyle, S.P. Urbanski, L. Hutyra, they were used for wood products, pasturage, S.R. Saleska, D. Fitzjarrald and K. Moore. and how they may have been managed. In a 2001. Factors controlling long- and short-term related project on recent forest cutting in central sequestration of atmospheric CO2 in a mid- and western Massachusetts, we will conduct latitude forest. Science 294:1688-1691. field surveys comparing the forest vegetation Goulden, M.L., J.W. Munger, S.-M. Fan, B.C. Daube and S.C. Wofsy, 1996a. Exchange of and soil characteristics between sites that were carbon dioxide by a deciduous forest: Response shown as wooded versus open on the 1830 to interannual climate variability. Science map; this will allow us to estimate the 271:1576-1578. percentage of stands mapped as woodlands in Wofsy, S.C., M.L. Goulden, J.W. Munger, S.M. 1830 that were subsequently cleared for Fan, P.S. Bakwin, B.C. Daube, S.L. Bassow and agriculture and enable us to determine the long- th F.A. Bazzaz, 1993. Net CO2 exchange in a mid- term legacies of 19 century land-use on latitude forest. Science 260:1314-1317. modern forests.

Massachusetts’ Woodlands in the Mid-19th Century: Where Were They, What Did They Look Like, and What Are Their Long-Term Legacies.

B. Hall, G. Motzkin, and D.R. Foster

The 1830 map of Massachusetts’ woodlands has been an important tool in numerous research projects conducted at the Harvard Forest. This map provides valuable insight into the histories of individual study locations and for the Massachusetts landscape

58

RP 1957 burn

YHDFLPH

wetland H RP HK RS WP BG EMSOLDF wet land

RP

500 m

Figure 1. Carbon exchange measurement sites at Harvard Forest. EMS is the location of measurements since 1992 (Barford et al. 2001, Goulden et al. 1996, Wofsy et al. 1993) and is surrounded by a 65-100 deciduous forest in a lowland area, dominated by red oak and red maple. Data for the EMS site were obtained via the Internet at ftp://ftp.as.harvard.edu/pub/nigec/HU_Wofsy/hf_data, and are currently posted only through December 2002. H indicates an eddy covariance tower in a hemlock forest. LPH (Little Prospect Hill site) is like EMS a deciduous forest dominated by red oak and red maple, but on an upper hill slope and with trees ages of 45 years or less within 200 m of the eddy covariance tower and older trees at greater distances. Arrows in the figure indicate direction and probable magnitude of nocturnal cold air drainage, which can influence C exchange measurements at night. RP indicates planted red pine stands, RS and BG indicate red spruce and black gum growing in a swamp, and HK and WP indicate eastern hemlock and white pine.

J. Hadley and P. Kuzeja

59

2.2 EMS: main Harvard Forest deciduous forest site 2 Little Prospect Hill: younger, higher, drier deciduous forest 1.8

1.6 1.4 1.2 1

0.8

0.6 0.4 0.2 Monthly carbon storage Mg / ha 0 -0.2

-0.4 -0.6 May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct 2002 2003

Hadley and Kuzeja: Figure 2

Figure 2. Estimated monthly ecosystem carbon storage for two sites at Harvard Forest from May 2002 through October 2003. Carbon storage estimates for the Little Prospect Hill site have been revised upward in the past year after eliminating data for SSW winds that appeared to show anomalously large carbo n releases, possibly generated by human activity and fuel combustion in the headquarters area of Harvard Forest.

1 0

-1

-2 -3 -4 -5 -6

Cumulative NEE (Mg C / ha) -7 -8 EMS Little Prospect Hill -9 May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct 2002 2003

Figure 3. Estimated cumulative net ecosystem carbon exchange (NEE) for two sites at Harvard Forest from Hadley and Kuzeja: Figure 3 May 2002 through October 2003. In this figure carbon uptake is plotted as a negative number, and carbon release is positive. Each point indicates cumulative NEE at the end of the month indicated on the x-axis. For site descriptions and explanation of the shorter record for EMS, see Figures 1 and 2.

J. Hadley and P. Kuzeja

60 2.4 2002: May-October C storage = 5.2 Mg C / ha 2.2 2003: May-October C storage = 4.2 Mg C / ha 2 1.8 1.6 1.4 1.2

age Mg / ha 1 0.8

bon stor 0.6 r a

C 0.4 0.2 0 -0.2 -0.4 -0.6 Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

Figure 4 . Estimated monthly carbon stHadleyorage at and the Kuzeja:Little Pro Figurespect Hill4 site for 2002 compared to 2003. Data co llectio n b e g an in May 2002 and data analysis has been completed through October 2003. For description of the Little Prospect Hill site, see Figure 1.

J. Hadley and P. Kuzeja

Assessing N Availability Through Multiple NO3-N concentrations (Figs. 1 and 2). This Resin Extractions Following the Onset of the suggests higher nitrification rates as well as Hemlock Woolly Adelgid higher NO3-N availability, possibly leading to increased NO3-N leaching and denitrification. S.S. Jefts and D.A. Orwig Uninfested and recently infested stands exhibited similar or greater NH4-N availability Introduced exotic pests can pose when compared with heavily infested stands serious perturbations to ecosystem function, indicating that the majority of NH4-N in particularly to nutrient cycling and nutrient heavily infested stands has been nitrified to availability. Using the context of a natural NO3-N. Interestingly, two sites that no longer experiment, the elimination of eastern hemlock have a hemlock component, exhibited different (Tsuga canadensis) by the introduced pest the responses. One previously infested site that hemlock woolly adelgid (HWA), we are able to was logged now exhibits extremely high NH4- obtain unique insights into the effects this pest N and NO3-N availability (21.21 and 22.35 mg has on N availability. This study examined N N/L, respectively) indicating lack of plant availability via ion exchange resins over the uptake as well the possibility for high NO3-N period of 1 year as well as over the growing leaching and denitrification. Another site season only and the efficacy of multiple resin which lost all hemlocks due to HWA 10 years extractions in a set of hemlock stands ranging ago and which previously had high N in HWA damage severity. Overall, heavily availability, has been replaced by black birch infested stands demonstrated higher available (Betula lenta) and now exhibits low N

61 availability (1.77 and 1.47mg N/L for NH4-N to Florida). The specific goals of the project and NO3-N) indicating increased plant uptake are: 1) to explore spatial patterns in foliar N as black birch continues dominance of the site. within the landscapes surrounding each site The recovery efficiency of using one resin using hyperspectral remote sensing; 2) to link extraction was lower in sites with high N spatial data for canopy N to tower-based C flux availability. This was most pronounced for measurements using an ecosystem simulation NO3-N indicating that more than one extraction model; and 3) to scale landscape-level carbon may be needed for sites with expected or fluxes and canopy traits to broad scale multi- known high N availability (Figs. 3 and 4). We spectral and multi-angle remote sensing data are currently analyzing corresponding soils through use of a coupled ecosystem and canopy data, which will be compared with the resin radiative transfer model. data as well as the variability in microclimate.

Salamanders and Benthic Invertebrates in Scaling Forest Canopy Carbon Flux from the Headwaters of Bolton Brook, Mount Sites to Landscapes Using Airborne Remote Wachusett, Massachusetts Sensing and Canopy Nitrogen Chemistry. H. Jensen-Herrin, D. Williams and E.A. J.P. Jenkins, L. Plourde, S.V. Ollinger, M.E. Colburn Martin, M-L. Smith, A.D. Richardson, D.Y. Hollinger and B.A. Braswell Headwater streams are at risk in Massachusetts from land development and Combining light use efficiency (LUE) pollution, and in some cases are not protected estimates with satellite-derived FPAR by environmental laws. Little attention has been represents the current state of the art in remote given to what role these streams serve in estimation of vegetation carbon uptake in supporting biodiversity on the landscape, or to terrestrial systems. A critical component of this their function as habitat or refugia for aquatic or approach involves understanding sources of terrestrial species. Gregory et al. (2002) variation in LUE and deriving methods for demonstrated that close to 85% of upland areas estimating LUE values both within and between in some parts of the Piedmont of North biomes. In one recent study, a simple index Carolina are drained by headwater streams, created from leaf N concentration, specific leaf making them an important physical interface weight and LAI was able to explain 85% of the between upland and higher order streams and observed variance in LUE across all species and rivers. The streams central to our study are biome types with foliar N being the most identified as “intermittent streams” that carry influential term. This suggests that improving water after storm events or during seasonal our understanding of variability in canopy N runoff, but have only subsurface or interstitial concentration variability and exploring new flow at other times of the year. The methods for scaling canopy N to the resolution salamanders, aquatic insects and fish using of the modern suite of global remote sensors these intermittent streams as habitat often will improve our ability to make broad scale extend their range and influence beyond the estimates of carbon uptake and productivity. stream banks into the surrounding terrestrial Here, we report on progress in a habitat, yet the species assemblages for research effort aimed at using remotely-sensed intermittent streams have not been well studied canopy nitrogen as a spatial scaling tool for in New England. integrating carbon flux estimates between eddy Between July 2002 and February 2003 covariance towers and broad-scale remote we mapped both intermittent and perennial sensing. The sites involved are all part of the AmeriFlux network and are located along a latitude gradient in eastern U.S. forests (Maine

62

Figure 1. Nitrate and ammonium values of yearlong deployment of resins by varying infestation levels.

Figure 2. Nitrate and ammonium values of resins deployed for the growing season by varying infestation levels.

S.S. Jefts and D. A. Orwig

63 Year long multiple resin extractions

100.00 90.00 80.00 70.00

60.00 uninfested 50.00 recently infested

percent 40.00 heavily infested 30.00 20.00 10.00 0.00 112233

NH4-N NO3-N NH4-N NO3-N NH4-N NO3-N first, second and third extractions

Figure 3. Percent of nitrate and ammonium captured by the first, second and third extractions of resins deployed for one year grouped by varying infestation levels.

6 month multiple resin extractions

100.00 90.00 80.00 70.00 60.00 uninfested 50.00 recently infested

percent 40.00 heavily infested 30.00 20.00 10.00 0.00 112233

NH4-N NO3-N NH4-N NO3-N NH4-N NO3-N first, second and third resin extractions

Figure 4. Percentage of nitrate and ammonium captured by the first, second and third extractions of resins deployed for the growing season (approximately 6 months) by varying infestation levels.

S.S. Jefts and D. A. Orwig

64 sections of the headwaters of Bolton Brook, a square analysis demonstrated significant small mountain stream on the Wachusett differences in both salamander and Mountain State Reservation, Worcester County, macroinvertebrate populations between town of Westminster, Massachusetts. Our goal intermittent and perennial stream reaches. was to examine the distribution of stream Salamander distributions differed significantly salamanders and macroinvertebrates, and between perennial and intermittent stream identify species assemblages in intermittent and reaches (X2 = 98.07, df = 3, p< 0.05) Fig. 2. perennial sections of the stream system. We Chi square analyses of frequencies of examined the effects of physical characteristics occurrence of all 4 species of salamanders including flow periodicity and substrate/habitat encountered by transect or quadrat in the stream types on the species assemblages. We also system based on the intermittent or perennial hoped to identify key organisms that might be nature of the stream channel returned useful indicators of stream class in central significant Chi 2 value (X2=98.79, df=3, Massachusetts. p=0.05). Spearman Rank Correlation showed On each 50 meter stream reach we an inverse relationship between Red-backed established random transects of 4M x half salamanders and stream width. Spearman Rank stream width (in meters) with a minimum of 4 x Correlation showed an inverse relationship 1 meters and searched them thoroughly for between Red-backed salamanders and stream salamanders. We recorded habitat variables width. Chi 2distribution calculated on the including substrate characteristics, gradient, frequency of occurrence of Trichoptera taxa flow, temperature, and presence of brook trout, between intermittent and perennial stream (Salvelinus fontinalis) for each transect. Visual types, demonstrated a significant Chi 2 value surveys for salamanders were also conducted (X2= 402.10, df=11, p=0.05) Fig. 1. throughout the study area. We sampled Multivariate analyses of habitat and substrate macroinvertebrates in a single, random, square- characteristics were used to identify specific meter quadrat in each 50-meter stream reach by habitat requirements or preferences for vigorously dipnetting in the surficial substrate, salamanders and selected macroinvertebrate live-picking all animals in the field, and species with less significant results. preserving then in 70 percent ethanol for later identification in the laboratory. Physical habitat variables were recorded as above for each Timber Harvest in a Fragmenting quadrat. Landscape Dominated by a Diversity of Three species of stream salamanders, Ownerships the northern dusky salamander, Desmognathus fuscus, the two-lined salamander, Eurycea D.B. Kittredge bislineata, and the spring salamander, Gyrinophilus porphyriticus, as well as the Earlier work with timber harvesting terrestrial Redbacked salamander, Plethodon regulatory data has documented its extent cinereus, were identified in the stream. All across a sample landscape in Massachusetts, three stream salamander species routinely co- and shown its random occurrence with respect occured with S. fontinalis in parts of the stream to biological, physical, or cultural features where the fish are present. The Redbacked (Kittredge et al. 2003). Subsequently, data salamander, Plethodon cinereus, appears to be have been collected for the entire state for 1997 using the damp organic debris in dry and – 2001, and are in the process of being intermittent portions of the stream channel as collected and reviewed for 1984 – 2001. In refugia during dry periods. Macroinvertebrate addition to their value of documenting an numbers and species richness declined with important form of anthropogenic disturbance, increasing stream intermittency and gradient. A these data are also useful to explore the extent key indicator species, Pseudostenophylax to which harvest as a management and uniformis, a caddisfly restricted to intermittent economic activity continues to occur in a streams, was identified in this system. Chi fragmenting forested landscape. Wear et al.

65

Trichoptera Species Assemblages by Flow Regime

8

6 es

eci 4 p S 2

0 pppppppppppppppiipiiii

BPA- BPA- BPA- BPC- BPC- BPC- BPC- BPC- BPD- BPD- BPD- BPD- BPD- BPE- BPF- BPG- BPG- BPH- BPH- BPH- BPH- BPH- 253 356 381 288 324 354 450 479 025 092 14 1 17 0 249 015 018 19 0 276 014 065 13 5 281 326 Perennial/Intermittent Quadrat

Aphropsyche Lepidostoma Molanna Oligostomis Parapsyche Phylocentropus Polycentropus Pseudostenophylax Ps ilotr eta Pycnopsyche Rhyacophila Wormaldia

Figure 1.

Salamander Species Assemblages by Flow Regime

4

3 s e i

c 2 e Sp

1

0 p p p p p p p p p p p i i i i BPA BPA BPC BPC BPD BPD BPD BPD BPE BPF BPF BPG BPG BPH BPH 240- 340- 280- 440- 100- 120- 160- 240- 0-20 0- 20 20-40 140- 180- 140- 240- 260 360 300 460 120 140 180 260 160 200 160 260 Perennial/Intermittent Transect

Northern Dusky Two-lined Northern Spring Red-backed

Figure 2.

H. Jenson-Herrin, et al.

.

66 (1999), for example, estimate that the More data on parcelization and harvest probability of harvesting approaches zero in a activity are needed for more rigorous analysis Virginia landscape where population density and to draw stronger conclusions, but exceeds 388 km-2. Barlow et al. (1998) showed preliminary results suggest there are distinct that distance from urban centers (>50,000 fragmentation and parcelization thresholds inhabitants) in Mississippi and Alabama was beyond which harvest ceases to be viable in positively and significantly related to the these otherwise forested landscapes. probability of harvest (estimated by FIA plots). If forested landscapes dominated by thousands Barlow, S.A., I.A. Munn, D.A. Cleaves, and D.L. of small family, NGO, and municipal Evans. 1998. The effect of urban sprawl on ownerships are to remain productive sources of timber harvesting. Journal of Forestry wood products (e.g., Berlik et al. 2002), it is 96(12): 10-14. important to understand the influences of Berlik, M.M., D.B. Kittredge, and D.R. Foster. 2002. The illusion of preservation: a global parcelization and fragmentation. environmental argument for the local Massachusetts forest cutting data for production of natural resources. Journal of 1997 – 2001, and timber tax data from New Biogeography 29: 1557-1568. Hampshire for 2001 (provided by M. Tansey, Kittredge, DB, AO Finley, and DR Foster. 2003. NH Division of Forests and Lands) were used Timber harvesting as ongoing disturbance to describe the extent of harvest on a town-by- in a landscape of diverse ownership. Forest town basis, in terms of the number of Ecology and Management. 180 (2003) operations km-2 and harvest volume 425–442 (m3)/hectare forest. Fragmentation of a town’s Wear, D.N., R. Liu, J.M. Foreman, and R.M. overall forest area was estimated by its average Sheffield. 1999. The effects of population growth on timber management inventories Mean Shape Index (MSI: an expression of in Virginia. Forest Ecology and perimeter: area ratio of a patch of forest, Management 118 (1999): 107-115. weighted by its size). Parcelization of a subset of towns in MA and NH (stratified by population density, n=55) was estimated using Environmental History of Two New England actual tabular tax assessor data, which provides Ponds: Natural Dynamics Versus Human the number and size of parcels. A number of Impacts metrics of parcelization were developed (e.g., percent of a town’s land in parcels > 10 D. Köster and R. Pienitz hectares; number of parcels/ hectare of land). Parcel data are not spatially explicit, so they Analyses of sedimentary diatoms and cannot be related to actual forest ownership, but stable isotopes in two New England ponds can only serve as a relative indication of the indicate limnological changes during the past degree of parcelization in a community. 2500 years related to climate change, anthropogenic activities and natural Preliminary results indicate: disturbance. Deforestation during the 18th and 19th centuries temporally affected diatom • As the percent of a town’s land in parcels > assemblages with subsequent recovery, but 10 hectares declines towards 40, the -2 algal communities did not return to pre- likelihood of harvest operations km settlement conditions due to natural approaches zero; disturbances, delayed recovery from -2 • Likelihood of harvest operation km forest acidification and continued climatic change. In area in NH approaches zero with a MSI > both lakes, short-term rises in diatom-inferred 1.8 DOC was related to partial removal of -2 • Likelihood of harvest operation km forest vegetation by logging or a hurricane in 1937 at area in MA approaches zero with a MSI > North Round Pond. At Levi Pond, increasing 2.2, implying harvest occurs in more diatom-inferred DOC concentrations during the fragmented forest

67 past ca. 2000 years seem to reflect a long-term fossil fuel impacts toward the end of the increase of allochtonous organic matter loading growing season. By constraining measurements and probably peat development in the to those collected between May-August, we watershed related to moister conditions, which were able to successfully derive the NEE-δ13C is supported by coincident patterns in stable value for the Harvard Forest. We also present isotope and vegetation composition. These the first weekly dataset of seasonal variations in 13 13 results correspond to moisture patterns in δ CR from these 3 forests. Combining δ C adjacent areas inferred by pollen and sediment values associated with respiratory and net analyses, suggesting that diatoms in Levi Pond fluxes, we demonstrate a method for estimating recorded a larger regional trend in increasing whole-canopy ∆A in terrestrial ecosystems moisture. Our results showed that long-term directly from field measurements. The δ13C trends in climate change and small-scale natural 13 associated with NEE fluxes (δ Cbio) at these disturbance patterns still contribute to dynamics forests range between –26.0 ± 2.8 and –27.8 ± of man-altered ecosystems. Furthermore, this 2.4 ‰. These estimates differ from a previous study suggests that fossil diatoms may be a 13 study, when δ C values of these ecosystems promising proxy for future paleohydrological bio were compared to forests at comparable studies in temperate regions. latitudes. Our observations indicate large

variations in the value of δ13C across 3 R Photosynthetic 13C Discrimination in North temperate forests (-24.9 ± 0.4 to -31.3 ± 0.6 ‰). Despite that no significant correlations American Temperate Forest Biomes 13 were found between δ CR and water status at 13 C. Lai, J. Ehleringer, A. Schauer, D. Hollinger, the Harvard Forest, monthly-mean δ CR values K.T. Paw U, J.W. Munger and S. Wofsy were significantly correlated with growing- season soil water availability for the two 13 coniferous forests. We suggest that shifts in the The δ C values of atmospheric CO2 13 δ C values of terrestrial CO2 fluxes are driven can be used to partition global patterns of CO2 source/sink relationships among terrestrial and by region-wide drought patterns that could be oceanic ecosystems using the inversion of sufficient magnitude globally to impact technique. This approach is very sensitive to partitioning calculations of CO2 sinks between estimates of photosynthetic 13C discrimination oceanic and terrestrial compartments. by terrestrial vegetation (∆A), and depends on 13 13 δ C values of respired CO fluxes (δ C ). 2 R Does Evolutionary Change in Resource Here we show that by combining two Allocation by Alliaria petiolata Drive independent data streams - the stable isotope Invasiveness? ratios of atmospheric CO and eddy-covariance 2 CO flux measurements - regional estimates of 2 K.C. Lewis and F.A. Bazzaz ∆ can be successfully derived in terrestrial A ecosystems. Annual mean, flux-weighted δ13C It has been hypothesized that values of net ecosystem CO exchange (NEE) 2 evolutionary change in species introduced to a were estimated for 3 forest ecosystems (Wind new location can enable the species to become River Canopy Crane, Harvard Forest and invasive. This hypothesis has been supported Howland Forest) by analyzing daytime flask by the observation of lag time between measurements collected at the top of canopies. introduction and invasion, and by observed Our approach was based on the assumption that alteration in size of plants introduced outside of variations in CO mole fraction observed in 2 their home ranges. Reduced herbivory is one terrestrial ecosystems were dominated by consistent change in selection pressure which biological activities during the growing season may result in evolution in the new location. (May – early October). Harvard Forest, Reduced herbivory could result in altered however, was found to experience significant allocation of resources to anti-herbivore

68 defenses, affecting growth and reproduction. The Rise and Fall (and Rise And Fall) of The expected patterns of change in defenses Spruce in Massachusetts after introduction depend strongly on the assumptions made about herbivore load change, M. Lindbladh, E. Faison, D.R. Foster, and herbivore identity, and resource availability. W.W. Oswald Our previous work analyzed the differences in sinigrin content in young leaves Due to difficulties in separating pollen of Alliaria petiolata in native and invasive from the three spruce species occurring in populations and found significantly higher eastern North America, little is known about concentrations of sinigrin in leaves from the their history. However, a method for the invasive populations in some cases. However, separation has recently been developed these differences in sinigrin content were (Lindbladh et al. 2002). The first application of strongly correlated with plant size, which is the method to eight sites in Maine showed a dependent on resource availability. In this shift from a forest of white spruce (Picea study, we investigated life-stage variation in glauca) and black spruce (P. mariana) in the sinigrin concentrations in Alliaria petiolata late glacial to a forest of red (P. rubens) and populations in its native Europe and in its new black spruce in the late Holocene (Lindbladh et range in the US. We utilized herbivore al. 2003). The small number of red spruce exclusion treatments to investigate the role of grains identified from the late glacial samples inducibility in geographic patterns of defenses. (<5%) suggested that that species was either Plants in European (native) populations absent or rare at most of the sites. However, the experienced significantly greater herbivore study included only one level from each site damage than plants in North American from the late glacial and late Holocene, (invasive) populations. Contrary to anecdotal respectively. evidence suggesting invasive species are larger In an ongoing study from several pollen in their introduced ranges, we found that plants sites in Massachusetts we have for the first time in the native populations were consistently applied the method to consecutive levels. One larger than those in the invasive locations. We of the sites investigated is Blood Pond in south- found no consistent difference between native central Massachusetts. This site showed high and invasive populations in sinigrin amounts of spruce pollen (as most ca 45%) concentration in either first- or second-year from ca 16,000 to 11,000 cal BP but recorded plants. There does not appear to be a pattern of almost no spruce pollen from there after. The induced production of sinigrin in response to preliminary results show that white spruce herbivory, nor does herbivory seem to be probably was the only spruce species at Blood dependent on sinigrin concentration of target Pond in the beginning of the record (Fig. 1). plants. The negative correlation of sinigrin Starting at ca 14,500 cal BP black content to leaf size and plant size was signficant spruce started to increase, and it had almost in the first-year plants, but was weaker in the entirely replaced white spruce by ca 13,500. second year, presumably due to reallocation of Very few grains were identified as red spruce. resources from defenses to reproduction at The pollen record shows two peaks of spruce flowering. Our data suggest that life stage and during the late glacial, a pattern that has been interannual variation in resource availability are observed at other nearby sites: the first ca the main determinants of allocation to defense 14,500 cal BP and the second at the beginning and growth, and suggest that there has been the Younger Dryas chronozone (12,900 – little evolutionary change in production of 11,600 cal BP). Our data show that the first sinigrin in A. petiolata since introduction into peak was dominated by white spruce and the North America. second peak consisted almost entirely of black spruce. The pattern with an initial dominance of white spruce and gradual replacement by black spruce is also present in the pollen record from

69 Berry Pond in northeastern Massachusetts, Soil Warming at Barre Woods: Megaplot although the record is not yet dated. Responses After One Year of Warming Our results suggest that the fluctuation in spruce pollen percentages before and during H. Lux, E.Burrows, J.M. Melillo, P.A. Steudler, the Younger Dryas should not be interpreted as F.P. Bowles, S. Morrisseau and A. Chan a range shift of a single species related to climate change (Shuman et al. 2002), but rather Will the increase in available nitrogen as a change in species composition during the resulting from soil warming lead to an increase period. in carbon storage in vegetation? And if yes, Following the interval of black spruce how much? To answer these questions we dominance, spruce pollen percentages dropped initiated a “mega-plot” soil warming study in dramatically and remained low for the next ca 2001, in the Barre Woods site in Harvard 7000 years. Then, starting around 4000 cal BP, Forest’s Slab City Tract.The study area is a spruce percentages began to increase at sites mixed deciduous temperate forest less than 100 across the region, presumably in response to years old. During the summer and fall of 2001 increasing effective moisture. We are currently we buried 5.7 km (3.4 miles) of heating cable at mapping the pattern of spruce pollen a 10cm depth in a 30 x 30m plot. We percentages across New England (Fig. 2), to delineated a second 30 x 30m area to serve as better understand the spatial and temporal the control plot. Results from the original soil variability of this late Holocene increase in warming experiment confirmed that the soil spruce abundance. In general, it appears that the disturbance associated with the installation of spruce increase occurred first (ca 4000-2000 cal heating cables has had no effect on soil BP) in the northern and western portion of this temperatures and only minor and variable region, including the Adirondacks, western impacts on soil moisture, as well as producing Massachusetts, and the northern parts of no significant effect on soil carbon and nitrogen Vermont, New Hampshire, and Maine. At sites dynamics. in coastal Maine and eastern Massachusetts, the In April of 2002 we began a one-year increase in spruce pollen percentages occurred period of baseline measurements before turning later (after 2000 cal BP). on the heat in the new megaplot. We saw no significant pre-treatment differences in CO2 Lindbladh, M., R. O’Connor and G.L. Jacobson, Jr., release, N2O flux or CH4 uptake from the soil 2002. Morphometric analysis of pollen between the two plots. Nitrogen mineralization grains for paleoecological studies: measurements revealed higher rates in the classification of Picea from eastern North turnover of soil N in the plot to be heated, as America. American Journal of Botany 89: 1459-1469. well as differences in the foliar chemistry of Lindbladh, M., G.L. Jacobson, Jr. and M. Schauffler. some species. We will account for these 2003. The postglacial history of three baseline differences to isolate ecosystem Picea species in New England, USA. responses due to heating. Quaternary Research 59: 61-69. We turned on power in May of Shuman, B., T. Webb, III, P. Bartlein and J.W. 2003 (Fig. 1), and the "manipulation phase" has Williams 2002. The anatomy of a climatic begun. After one year of heating, monthly CO2 oscillation: vegetation change in eastern flux (Fig. 2) increased an average of 30.8% and North America during the Younger Dryas nitrogen mineralization (Fig. 3) increased an chronozone. Quaternary Science Reviews average of 38.4%, total understory biomass 21: 1777-1791. increased 45%, and foliar nitrogen increased, significantly in birch (22%) and ash (9%) species. Minimal nitrogen left the system

through leaching (measured using lysimetry) or

gaseous (N2O) emissions. Monthly dendrometer band measurements on all trees in

70 Blood Pond, MA Total spruce 40 20 0 11500 12000 12500 13000 13500 14000 14500 15000 40 White spruce 20 0

llen 11500 12000 12500 13000 13500 14000 14500 15000 40 l po Black spruce

ta 20 0 11500 12000 12500 13000 13500 14000 14500 15000 % of to 40 Red spruce 20 0 11500 12000 12500 13000 13500 14000 14500 15000 40 Undiff. 20 0 11500 12000 12500 13000 13500 14000 14500 15000 cal year BP

Figure 1. Pollen diagram from Blood Pond, MA. Undiff. denotes spruce pollen with intermediate characters that can not be differentiated to species. Thirty grains per level are analysed.

# #

# # Maine

# # #

# # # # # # ## ## # # # # Vermont # # #

New Hampshire New York # GpCald&ibrahtedf_s 14prCu ycee2ars.d BbfP # # # # # 0 - 500 # # # # # 500 - 1000

Massachusetts # 1000 - 1500

# 1500 - 2000 R.I. Connecticut # 2000 - 2500 # 2500 - 3000

# 3000 - 4500

Figure 2. Map showing the locations of selected pollen records in the northeastern United States. Symbol size indicates the timing of the initial increase of spruce pollen percentages during the late Holocene

M. Lindbladh et al.

71

CTRL_AV 25 P1_AV 23 P2_AV 21 P3_AV P4_AV 19 P5_AV 17 P6_AV

Degrees Celcius 15 P7_AV P8_AV 13 P9_AV 11 P10_AV 245 246 248 249 251 252 254 255 257 258 260 261 263 264 266 267 269 270 272 DAY

Figure 1. Continuous thermister data from the Barre Woods soil warming plots, demonstrating system control of temperature differential. X-axis is day of the year. Data is from September, 2003.

350

Shading demarcates the pre-treatment period. 300 ) -1 250 hr -2

200 g Cm

150 eased (m rel 2 100 CO

50

0 May Jun Jul Aug Sep Oct Nov Dec Apr May Jun Jul Aug Sep Oct Nov 2002 2003

Figure 2. Monthly total soil respiration at the Barre Woods Megaplot Experiment, pre-treatment and with heating. Error bars indicate standard error of the mean.

H. Lux, et al.

72 standa Fi Allo Fi gure 3. gure 4. m rd error e tric eq H. Lux M M o o uatio nt nt of them , hl hl

-1 -1 et al -1 Net N Mineralization (kg N ha mo ) y y Total Biomass Additions kg ha n net oa 10 15 20 25 30 s -1 0 5 10 20 30 40 50 60 are . 0 k, ean 0 0 0 0 0 0 0 0

Ni m u Ma t . s a r ed with o y pl No g S e, bi Ju en h v n a m d J J i u rc u n n l

i g m neral h a dema Au ont S J u g h n l adi d as hl i Se 2 z rcates Au 002 p n at y g g

h i Oc dem wo on at 20 t bi Se thep 02 o No p om a d rcates v t y Oct h ass addi i De re- e B n c c trea thepre- r N Ja em a ov 73 n r t r m e Fe ent t Ap

ent peri i b Woo ons at r treatm m Ma Ma r easurem d y Ap s o t e M d r h n Ju . t peri e B Ma n e y ga a ent 2 Ma Ju od. r pl 003 r l 200 y e ot s t A Ju Wo E 3 u o n g est x o Ju peri Se d l i p Oak Oak s M Mapl Map Ash C A Bi Bi m Au s m rch rch h a g Co He Oct Heat Heat C t l e e e e e Heat C Se nt o g o Con Heat bi a n n n p o a t t . t t Nov n e e pl r r ed rol om o t o d d Oc ed Er ol t l ed ot r l o t

l ass addi ro E r x bars peri

m i t i ndi ons e nt cat . . e the plots clearly reveal seasonal growth Salamanders in Eastern Hemlock Stands – patterns, as well as the dominance of the site by The Forgotten Forest Fauna red oak (Quercus rubra L.) (Fig. 4). We detected no significant differences in growth B. Mathewson, E. Colburn and D.R. Foster due to heating after six months of heating. The story of the changes taking place at this site will Eastern hemlocks (Tsuga canadensis) continue to unfold this summer. within central Massachusetts are threatened by the hemlock woolly adelgid (HWA; Adelges tsugae), an introduced pest that causes high Ecosystem Response to 15 Years of Chronic mortality (Orwig and Foster 1998). Several Nitrogen Additions. bird and mammal species have been found to be strongly associated with eastern hemlock A.H. Magill, J.D. Aber, W. Currie, K.J. forests (Yamasaki et al. 2000). However, little Nadelhoffer, M.E. Martin, W.H. McDowell, research has been conducted on salamander J.M. Melillo and P. Steudler associations with this forest type (Brooks 2001). This omission is significant given that Anthropogenic nitrogen deposition has the terrestrial salamander biomass has been found potential to alter nitrogen cycling patterns and to equal the biomass of small mammals and be processes in ecosystems. The long-term impact twice that of breeding birds at the Hubbard of elevated nitrogen inputs was studied in two Brook Experimental Forest in New Hampshire temperate forest stands at the Harvard Forest (Burton and Likens 1975a). LTER site. Key indicators of nitrogen This study compared the abundance of saturation, including forest productivity, foliar juvenile eastern red-spotted newts, or red efts chemistry, and soil solution chemistry, were (Notophthalmus viridescens viridescens) and measured in red pine and mixed hardwood adult and juvenile eastern redback salamanders stands receiving six NH4NO3 additions over (Plethodon cinereus), in eastern hemlock and each growing season from 1988 to 2002. Four hardwood stands at five sites. These sites were treatment plots were located in each stand with located within the Prospect Hill, Simes, Slab the following application rates: 0 (control), 5 City, and Tom Swamp tracts of Harvard Forest (low N) and 15 (high N) g N m-2 yr-1. in Petersham, MA. I sampled salamander Aboveground biomass was severely impacted abundance through visual surveys along 90 m2 with red pine mortality reaching 56% by 2002 transects, intensive searches of 1 m2 quadrats, in the pine high N plot. (See photo cover). The and installation and monitoring of artificial hardwood high N plot showed increased ANPP, cover objects (ACOs) that served as potential but a severe drought in 1995 contributed to refugia in the late summer and fall of 2003. I mortality of 72% of red maple trees by 2002. also evaluated whether individual species’ Species importance and litterfall patterns were distributions varied in relation to soil pH. I altered in several plots after 1995. Foliar and used 2-sample t-tests to compare salamander fine root N concentrations in treated plots abundance between stands within species. increased 25 – 80% over control plot values. N. v. viridescens abundance (Fig. 1; Inorganic N leaching below the rooting zone Table 1) as measured by visual surveys along (60 cm) were elevated in both high N addition transects was significantly greater (P < 0.01) in plots starting as early as 1990 (pines) and 1995 eastern hemlock stands than in hardwood (hardwoods). Roots, foliage, and wood have stands. Intensive searches of 1 m2 quadrats also diminished as net sinks for added N, yielded results suggesting N. v. viridescens emphasizing the role of soils in N retention. were more abundant (P < 0.10) in eastern Two mechanisms for large net retention of hemlock stands than in hardwood stands. N. v. added N are proposed: abiotic N viridescens were found under ACOs only once immobilization and assimilation and re- and on top of ACOs twice. N. v. viridescens exudation by mycorrhizae. was found to be negatively correlated with pH (transect walks: correlation = -0.518 P < 0.01;

74 intensive searches: correlation = -0.390 P < Method for Monitoring Populations of the 0.10). Redback Salamander Plethodon cinereus. P. cinereus are nocturnal and only one Journal of Herpetology, Vol. 34, No. 4, pp. 624- individual was encountered on visual surveys of 629. transects. No evidence was found that P. Orwig, D.A., D.R. Foster. 1998. Forest response to the introduced woolly adelgid in southern New cinereus was more abundant in hardwood England, USA. J. Torrey Bot. Soc. 125, 60-73. stands from cover board monitoring (P = 0.98) Yamasaki, M., W.B. DeGraaf, and J.W. Lanier. as abundance was higher in all five sites in 2000. Wildlife habitat Associations in Eastern eastern hemlock stands. However, P. cinereus Hemlock—Birds, Smaller Mammals and Forest abundance as measured by intensive searches of Carnivores. Proceedings: Symposium on 1 m2 quadrats was significantly greater (P < Sustainable Management of Hemlock 0.05) in hardwood stands than in eastern Ecosystems in Eastern North America (eds K.A. hemlock stands (Fig. 2; Table 1). P. cinereus McManus, K.S. Shields and D.R. Souto) pp. abundance was unrelated to soil pH (P > 0.25). 135-143. USDA General Technical Report 267. Our research suggests that eastern Newtown Square, PA. hemlock mortality caused by HWA and the conversion of eastern hemlock stands to hardwood stands may cause decreases in Sugar Biomarkers as Source Indicators of juvenile N. v. viridescens abundance in these Biogenic Organic Carbon in Aerosols stands during the late summer and fall as both Collected at the Howland Experimental methods yielding data regarding this species Forest, Maine found evidence of a higher abundance in eastern hemlock stands. It is unclear how P. P. Medeiros, M.H. Conte, J.C. Weber and B.R cinereus abundance would be affected within T. Simoneit these stands as the methods used to measure this species abundance produced contradictory Bulk aerosols (>1 µm) were collected results. Future research should test the continuously above the Howland forest canopy hypothesis that the results from the intensive from May – October 2002. Each sample searches in this study are accurate in suggesting integrated approximately a two week period. that P. cinereus abundance is higher in Soluble mono- and disaccharide sugars were hardwood stands, and that this species’ extracted using a direct microscale extraction abundance appears higher in eastern hemlock method and were analyzed as their TMS stands when monitoring ACOs because cover is derivatives by GC-MS. limiting in these stands. This could be tested by Concentrations of total aerosol sugars intensively searching areas surrounding ACOs ranged from 10 to 160 ng m-3. Glucose (α and before and after removing them to determine if β) was the most abundant sugar (30-60% of there is a greater increase in P. cinereus total sugars). The monosaccharides arabinose, abundance after ACOs are removed in eastern fructose, galactose, xylitol and sorbitol, and the hemlock stands. A similar technique was used, disaccharides sucrose, maltose and mycose (aka and found that cover was not limiting in a red trehalose) were also present in lower oak – white pine forest (Monti et al. 2000). concentrations. The sugar composition in the aerosols varied seasonally. Fructose and Brooks, R.T. 2001. Effects of the removal of sucrose were more prevalent in early spring and overstory hemlock from hemlock dominated decreased in relative abundance as the growing forests on eastern redback salamanders. Forest season progressed. Reduced sugars (xylitol and Ecology and Management. 149: 197-204. Burton, T.M. and G.E. Likens. 1975a. Salamander sorbitol) and the disaccharides maltose, a populations and biomass in the Hubbard Brook microbial degradation product of starch, and Experimental Forest, New Hampshire. Ecology mycose, a fungal metabolite, were more 56, 1068-1080. prevalent in autumn. The changes in the sugar Monti, L., M. Hunter, Jr., J. Witham. 2000. An Evaluation of the ArtificialCover Object (ACO)

75 Juvenile eastern red-spotted newt (Notophthalmus viridescens viridescens) Abundance

0.300

Transect Walks e

r 0.250 Intensive searches

0.200 r squa r te 0.150 pe me s v 0.100

Indi 0.050

0.000 1 2 4 4 * * * S1 S2 S3 5 5 S* T T T W3 TS W HW HW H HW TS HW t - T o t - H T o T Stands

Figure 1. Notophthalmus viridescens viridescens abundance as measured by visual surveys of transects and time constrained (2-minute) intensive searches of 1-m2 quadrats (TS – hemlock stand; HW – hardwood stand). * significant difference between stand types as measured by transect walks at P < 0.01

Eastern redback salamander (Plethodon cinereus ) Abundance ACO Monitoring 1.8 Intensive searches

e 1.6 r 1.4

qua 1.2 r s r te 1 pe

me 0.8 s 0.6

ndiv 0.4 I 0.2 0 1 2 3 3 4 4 5 5 * * W1 W2 W W W W TS TS TS TS TS TS H H H H H - H t t - ToTo Stands

Figure 2. Plethodon cinereus abundance as measured by monitoring of ACOs and time constrained (2-minute) intensive searches of 1-m2 quadrats (TS –hemlock stand; HW –hardwood stand). * significant difference between stands as measured by intensive searches at P < 0.05

B. Mathewson, et al.

76 Table 1. Summary of the abundance of juvenile eastern red-spotted newts, or red efts (Notophthalmus viridescens viridescens) and adult and juvenile eastern redback salamanders (Plethodon cinereus) in eastern hemlock stands and hardwood stands.

Experiment N Mean Std SE (per Dev Mea m2) n P. cinereus abundance as measured by ACO monitoring 363 1.456 0.63 0.03 in hemlock stands (N = number of ACOs) 1 3 P. cinereus abundance as measured by ACO monitoring 180 1.044 0.50 0.03 in hardwood stands (N = number of ACOs) 0 7 Two-sample t-test Tot HW = Tot TS (vs >): T = -2.06 P = 0.98 DF = 438 P. cinereus abundance as measured by time-constrained 100 0.080 0.27 0.02 intensive searches in hemlock stands (N = number of 1- 3 7 m2 quadrats searched) P. cinereus abundance as measured by time-constrained 100 0.180 0.41 0.04 intensive searches in hardwood stands (N = number of 1- 1 1 m2 quadrats searched) Two-sample t-test Tot HW = Tot TS (vs >): T = -2.03 P = 0.022 DF = 171 N. v. viridescens abundance as measured by transect 119 0.0271 0.04 0.00 walks in hemlock stands (N = number of 90-m2 transects 17 38 searched) N. v. viridescens abundance as measured by transect 65 0.0083 0.02 0.00 walks in hardwood stands (N = number of 90-m2 10 26 transects searched) Two-sample t-test Tot TS = Tot HW (vs not =): T = 4.06 P = 0.001 DF = 180 N. v. viridescens abundance as measured by intensive 100 0.11 0.37 0.03 searches in hemlock stands (N = number of 1- m2 3 7 quadrats searched) N. v. viridescens abundance as measured by intensive 100 0.04 0.19 0.02 searches in hardwood stands (N = number of 1- m2 7 0 quadrats searched) Two-sample t-test Tot TS = Tot HW (vs not =): T = 1.66 P = 0.099 DF = 150

B. Mathewson, et al.

composition in the aerosols reflected during this time. Glucose, galactose, and to a seasonality in the relative production of sugars lesser extent arabinose also increased in in the ecosystem, with greatest synthesis of concentration by factors of 2-5 in the smoke- simple sugars at the beginning of the growing impacted samples, indicating the fires may have season, and greater contributions of metabolites also enhanced atmospheric emissions of from microbial degradation of primary uncombusted organic materials. In contrast, compounds during the early autumn period of concentrations of arabinose, fructose, reduced leaf senescence and decay. sugars and the fungal metabolite mycose were Smoke plumes from Quebec forest fires passed not significantly higher in the smoke-impacted over the Howland site in late June and early samples and indicated that biomass burning was July 2002. Levoglucosan, a degradation product not a significant source of these compounds in of cellulose combustion and a biomarker of aerosols. biomass burning, increased by an order of magnitude in the aerosol samples collected

77 Soil Warming on Prospect Hill: The First of the controls, and 44% lower in the Decade and Beyond (1991-2003) mineral horizon. • The cohort of microbes that were J.M. Melillo, P.A. Steudler, H.B. Lux, E.H. present in the heated plots Burrows, J.D. Aber, F.P. Bowles, E. demonstrated different respiratory Farnsworth and A. Chan responses to a variety of added substrates than those in the control In the first decade of the Prospect Hill plots. soil warming experiment at the Harvard Forest, • Soil analyses revealed less labile C in we documented changes in soil carbon and the heated plots relative to the controls. nitrogen cycling. We showed that while soil Understory vegetation (study done by Elizabeth warming accelerates soil organic matter decay Farnsworth, New England Wild Flower and CO2 fluxes to the atmosphere, this response Society) is small and short-lived for a mid-latitude forest • Measurements made in the early years because of the limited size of a microbially- of soil warming (1992-1993) showed: accessible soil carbon pool. We also showed 1) acceleration of herbaceous plant that warming increases the availability of emergence in the spring in heated plots; mineral nitrogen to plants. Since plant growth 2) decreased species richness in heated in many mid-latitude forests is nitrogen limited, plots; and 3) increased relative diameter warming has the potential to indirectly growth of woody vegetation. stimulate enough carbon storage in plants to at • The same measurements were made least compensate for the carbon losses from in 2003, and the effects of soil warming soils. had changed over the course of 13 In years 11, 12 and 13 of the study, the years. For example, relative diameter effect of warming on soil carbon losses has growth of woody vegetation was remained small (Fig. 1). The large increase in significantly lower in heated plots, and available nitrogen created early on in response species composition had diverged to warming has begun to diminish somewhat among the three treatment types. (Fig. 2), although nitrogen leaving the system in soil water or N2O has not increased. We still do not know where the "excess" available Impacts of Aerosols and Clouds on Forest- nitrogen has gone, but speculate that over time, Atmosphere Exchange it is becoming tied up in nitrogen pools with long storage times such as refractory soil Q. Min organic matter and the woody tissue of the trees (Fig. 3). We are testing these ideas in a large- The impact of aerosols and clouds on plot soil warming experiment at Barre Woods. CO2 uptake and water use efficiency at Harvard Additional findings from the soil Forest has been studied by using collocated warming study at Prospect Hill include the turbulent flux and radiation measurements. We following: developed a fast retrieval algorithm for Methane uptake - Between 1991 and 2003, the synthesizing the visible spectrum from multi- average net uptake rate of CH4 by the narrowband instruments (MFRSR) and applied soil system in the heated plots was it to predict the Action PAR (CA_PAR) by about 17% higher than in the convolving with a normalized action spectrum disturbance control plots (Fig. 4). of plants. Taking advantage of simultaneous Microbes and labile carbon in 2003 (see Smith measurements of direct and diffuse spectral et al. this volume). irradiances from a MFRSR, we quantitatively • Active microbial biomass is 26% studied issues of “diffuse use efficiency”, CO2 lower in the organic horizon of the uptake efficiency and water use efficiency and heated plots than in the organic horizon cataloged the impact of aerosols and clouds through photosynthesis on CO2 uptake.

78 30 ) *100 DC )/ 20 ed ((H - DC s a

e 10 l e Carbon R

n 0 i e

% Chang -10 91-93 92-94 93-95 94-96 95-97 96-98 97-99 98-00 99-01 00-02 01-03 3 Year Running Means

Figure 1. Percent changes in carbon release in response to soil warming. Data are presented as three-year running means.

160 *100 )

DC 140

120

100 on ((H - DC)/ i t a z 80

nerali 60 n Mi e

g 40 ro Ni 20 in e

ang 0 h

% C 91-93 92-94 93-95 94-96 95-97 96-98 97-99 98-00 99-01 00-02 01-03 3 Year Running Means Figure 2. Percent changes in nitrogen mineralization in response to soil warming. Data are presented as three- year running means.

J.M. Melillo et al.

79 No gaseous No gaseous No gaseous No gaseous loss loss loss loss

Available nitrogen ( )

Slightly recalcitrant N ( )

Very recalcitrant N

Νο leaching Νο leaching Νο leaching Νο leaching

Year 0 Year 4 Year 8 Year 12

Figure 3. Nitrogen availability conceptual model. Year 0: Soil temperature is increased by 5o C. Year 4: N mineralization rates more than double. Increases in available carbon and nitrogen greatly increase potential for carbon storage by trees. Year 8: With time, increases in N mineralization rates begin to decline, but woody storage continues to increase as nitrogen moves through the system. Year 12: Nitrogen mineralization rates head towards a new equilibrium as nitrogen sources mobilized by a 5o C increase in temperature are depleted and the pulse of nitrogen continues to move through the system.

1.2 Disturbance Control 11% Heated

1.0

) 13% -1 26%* yr -2 23%*

m 29%*

0.8 C

g 1%

0.6

) Flux ( 17%* 4 H C

e ( 0.4 an th e M 0.2

0.0 91 92 93 94 95 96 01 02 03 19 19 19 19 19 19 20 20 20 Year * indicates significant difference between DC and Heated

Figure 4. Annual CH4 uptake at the Harvard Forest soil warming experiment. Measurements were made April – November.

J.M. Melillo et al.

80

Optical properties of aerosols and clouds have distribution) on photosynthesis due to variations significant impacts on photosynthesis not only of aerosols and clouds in the atmosphere. through changes of the total amount of PAR, Fig. 3 shows scattergrams of measured but also through changes of its spectral CO2 uptake flux against effective CA_PAR distributions (or light quality) and its under different sky conditions for the growing partitioning between direct and diffuse season of 1998 at the Harvard Forest site. The components. Fig. 1 shows scatterplots of direct “diffuse use efficient” coefficients under and diffuse CA_PARs against optical depths of aerosol and patch/thin cloud conditions are 1.95 aerosols and clouds in three atmospheric and 3.40 with maximum correlation coefficients categories: aerosols, thin clouds, and thick of R 2 , 0.62 and 0.71, respectively. This means clouds. For a given optical depth, the that under patch/thin cloud conditions the atmosphere loaded with aerosols has higher enhanced diffuse irradiance due to clouds is direct CA_PAR and lower diffuse CA_PAR more efficiently intercepted by the forest and than with thin clouds. Clouds enhance diffuse thus increases carbon assimilation. irradiance at longer wavelengths much more Furthermore, the efficiency of carbon uptake effectively than aerosols. The averaged values increases from aerosols, patch/thin clouds, to of direct and diffuse CA_PARs for optical thick clouds, as summarized in Table 1. Under depths between 0.44 and 0.46 are 0.295 and thick cloud condition the CO2 uptake efficiency 0.187 mmol m-2s-1 under aerosol conditions, is about 57% and 13% higher than under and 0.234 and 0.272 mmol m-2s-1 under thin aerosol and patch/thin cloud conditions, cloud conditions, respectively. The ratio of respectively. direct CA_PAR to diffuse CA_PAR The WUE, shown in Fig. 4, also shows dramatically changes from 1.57 under aerosol significant enhancement as atmospheric conditions to 0.86 under thin cloud conditions, conditions change from aerosol to thick clouds. i.e. the diffuse CA_PAR is substantially The WUE under thick cloud condition is almost enhanced under thin cloud conditions. The total 5 and 3 times greater than under aerosol and CA_PAR (direct + diffuse) under thin cloud patch/thin cloud conditions, respectively. The conditions is about 5% more than under aerosol primary reasons are that moisture in the forest conditions. is enhanced due to the presence of clouds, and To illustrate the importance of spectral transpiration is enhanced due to the enhanced variation of PAR, we compare the reconstructed CO2 uptake efficiency. In addition to changes in PARs by convolving with the normalized action moisture, the presence of clouds can both cause spectrum (CA_PAR) and the response function and be the consequence of changes in many of LICOR sensors (LICOR_PAR). Fig. 2 atmospheric factors such as temperature, latent shows ratios of CA_PAR and LICOR_PAR heating, VPD, and stomatal dynamics. We may under three categories of atmospheric conclude that an increase of radiation level conditions for solar zenith angles between 55 might not be the only factor responsible for the and 60 degrees. This ratio indicates the portion enhance carbon assimilation. Changes in many of LICOR_PAR that directly involves in the other factors, such as temperature, moisture, photosynthesis process. Under aerosol latent heating, and precipitation, in the presence conditions, the ratio slightly deceases with of clouds may have direct and indirect increasing of aerosol optical depth. Under thin influences on carbon assimilation and water use and thick cloud conditions, the ratio increases efficiency. from 0.55 to 0.75 as cloud optical depth increases. It indicates that spectral distributions of PAR under cloudy conditions are more favorable to plant photosynthesis than under aerosol conditions. It demonstrates the importance of light quality (spectral

81 Satellite Observations of Forest-Atmosphere 2000. The solid dots represent cases under Exchanges cloud conditions when the averaged SW radiation was less than 250 W/m2. The straight Q. Min and B. Lin line represents a least squares fitting between the EF and the MEDI. The correlation Developing remote sensing techniques coefficient ( R2 ) between the EF and the MEDI to observe biosphere processes is extremely is 0.51 for vertical polarization and is greater useful for studies of regional and larger scale than 0.40 for horizontal polarization. In the variations as the land surface types change following study, we will mainly use the induced by natural and anthropogenic MEDI_V. During transition periods of early influences. Satellite remote sensing is growing season and leaf senescence potentially a unique tool for this purpose. In this (MEDI<0.014), there was no sign of water paper we use an integrated approach that stress in both years, and thus water availability combines multiple-platform/multi-spectrum was not a limiting factor in ET. The visible, infrared, and microwave observations transpiration determined by the stomatal from surface and satellites to estimate resistance changes with the leaf physiology of microwave land surface emissivity (MLSE). the forest. The transpiration process plays By linking MLSE with collocated surface dominant role in regulating ET during the early turbulent and radiative fluxes over dense forest spring and later summer. However, during the area, Harvard Forest, we demonstrate the utility growing season when the canopy resistance was of satellite remote sensing to monitor surface low, the EF increased with MEDI_V but land-atmosphere exchanges. More importantly, showed much less correlation. Evaporation MLSE can be derived from satellite process of intercepted water on leaves could measurements during both day and night times have a significant impact on the ET process in with minimum influences from the atmosphere. these cases. When a vegetation layer is present over The ET process also strongly depends the soil surface, it attenuates soil microwave on the availability of energy to the canopy. Fig. emission and adds its own contribution to the 2 shows a scattergram of observed ET and radiation above the vegetation layer. The newly defined an ET index: ETI = MEDI * SW . optical depth of vegetation at microwave The solid line represents a linear least squared wavelength relates to vegetation water content fitting, indicating a good correlation between (VWC) and canopy structure and varies the MEDI_V and the ET, The correlation systematically with frequency. This coefficient of R 2 is 0.89, much better than that characteristic prompts us to define a new index of the EF vs. MEDI because ET is essentially based on emissivity difference between two decided by SW energy inputs and vegetation frequencies to understand vegetation dynamics, states. It further demonstrates an intrinsic i.e., the microwave emissivity difference index linkage of the MEDI to biophysical parameters (MEDI) as of canopy. It is worth to notice that the ET MLSE p − MLSEP index is fully defined by remote sensed MEDI p = A B . p P parameters from satellite measurements. The 0.5(MLSEA + MLSEB ) We will apply MEDI data derived from 19.4 high correlation between the ET and the ETI Ghz, and 37.0 Ghz channels of Special Sensor demonstrates that we can solely use remotely Microwave/Imager (SSM/I) measurements to sensed data from a combination of investigate their potential for detecting measurements from optical, infrared, and vegetation physiology changes and estimating microwave sensors to accurately estimate ET. surface land-atmosphere exchanges. Quantification of carbon stocks and Fig. 1 shows scatterplots of the derived fluxes is a key objective for ecosystem and evapotranspiration (ET) fraction (EF), carbon cycle studies. The CO2 uptake fluxes EF = ET /Q, at the Harvard Forest site against are strongly related to vegetation characteristics the satellite retrieved MEDI for years 1999 and and PAR fluxes. As demonstrated previously, the MEDI has an intrinsic linkage to

82 biophysical parameters of canopy. We further future net ecosystem productivity (NEP). exploit the feasibility of utilizing remotely Using data on pre-treatment and post-treatment o sensed MEDI to estimate CO2 uptake flux. As growth of 11 tree species, we found that a 5 C ET flux cases, the products of the MEDI and increase in soil temperature caused a 50% observed surface PAR are well correlated enhancement in understory productivity 2 ( R >0.6) with the CO2 uptake observations at (p<0.0001, Fig. 1). The magnitude of the Harvard Forest (Fig. 3). Again, the surface heating effect was negatively correlated with PAR can be estimated accurately from satellite intrinsic growth rate, so that warming measurements in optical wavelength domain. preferentially benefited slower-growing taxa Therefore, remotely observing land surface- (Figs. 2 and 3). Of the six species that atmosphere exchange of moisture and CO2 exhibited significant growth enhancements from satellite is possible, which provides a vital from warming, five were the slowest growing means in studies of regional- and global-scale taxa under control conditions: Fraxinus ecosystems and climate changes. americana (p=0.01), Tsuga canadensis (p=0.005), Quercus velutina (p=0.01), Acer saccharum (p=0.001), and Prunus serotina Soil Warming Hastens Successional (p=0.07). The sixth species, Acer rubrum, had Dynamics in a Temperate Forest Ecosystem intrinsically rapid growth under control conditions but additionally grew faster with soil J.E. Mohan, F.A. Bazzaz, E. Burrows, H. Lux warming (p=0.003). In contrast, fast-growing and J.M. Melillo species like Betula alleghaniensis, B. lenta, and Acer pennsylvanicum exhibited negligible Extratropical forests of the Northern responses to warming. These results may Hemisphere are currently important sinks for partially explain the large contemporary atmospheric carbon dioxide (CO2), largely due increase in A. rubrum abundance, and suggest to forest regrowth on abandoned agricultural that future forests may cycle more rapidly land. At the Barre Woods site in Harvard through successional development. Long-term Forest, we tested the hypotheses that soil carbon uptake by forests may be less than warming could affect forest regeneration suggested by current estimates based on highly- dynamics by preferentially benefiting either productive aggrading stands, and projections of highly-productive or slow-growing understory biotic feedbacks to the global carbon cycle may tree species - potentially altering rates of forest require revision. succession with accompanying implications for

Table 1. Diffuse-use-efficiency, CO2 uptake efficiency, and water use efficiency under three categories: aerosol, thin and/or patchy clouds, and thick clouds. Carbon uptake efficiency Diffuse use Water use efficiency Correlation efficiency (umol/mmol) mg/g Coefficient ( R 2 ) Aerosols 1.95 20.6 0.62 5.3 Patch/Thin clouds 3.40 28.7 0.71 8.7 Thick clouds NA 32.3 0.71 26.3

Q. Min

83

Figure 1. The direct and diffuse CA_PAR vs. optical depths of aerosols and clouds under three categories: aerosols, thin clouds, and thick clouds.

Figure 2. Ratios of CA_PAR to LICOR_PAR under three sky conditions for solar zenith angles between 55 and 60 degrees during the growing season of 1998 at the Harvard Forest site.

Q. Min

84

Figure 3. Scattergrams of direct, diffuse, and effective CA_PAR vs. measured CO2 uptake under aerosol, patch/thin cloud, and thick cloud conditions.

Q. Min

85

Figure 4. Scattergrams of total effective CA_PAR vs. measured WUE under aerosol, patch/thin cloud, and thick cloud conditions.

Q. Min

86

Figure 1. EF as a function of MEDI_V and MEDI_H for years 1999 and 2000.

Q. Min and B. Lin

87

Figure 2. ET as a function of MEDI_V for years 1999 and 2000.

Figure 3. CO2 uptake fluxes as a function of MEDI*PAR for years 1999 and 2000.

Q. Min & B. Lin

88 50 CONTROL 40 HEATED 30

20

10

0

-10

-20

-30 2000-2001 2001-2002 2002-2003 n.s. n.s. p<0.0001 pre-treatment pre-treatment post-treatment

Figure 1 Heated plants grow on average 50% faster after soil warming begins.

5 of 6 responders are slowest growing taxa

200

CONTROL *** 150 HEATED ** *** *** 100

**** * 50

0

-50

Increasing Growth in Control Plot →

Figure 2

J.E. Mohan, et al.

89 160

140 red maple

120 hemlock 100

80 black oak sugar maple 60 white ash

40 black cherry

striped maple 20 white pine red oak sweet birch 0 yellow birch

-20

-40 white oak 0.05 0.1 0.15 0.2 0.25 0.3 Intrinsic Growth Rate (mean growth in Control plot, 2002 & '03) Figure 3

J.E. Mohan, et al.

Twenty Years of Forest Harvesting Across high frequency of harvesting; approximately Massachusetts: Influences on Stand 1.5% of the forest area is logged annually in a Composition and Invasive Plant Species spatially random pattern that has left few large forest blocks undisturbed over the past 20 years G. Motzkin, D.R. Foster, D. Kittredge, J. Burk, (Kittredge et al., 2003). Mean harvest intensity B. Hall and J. Hall is 44.7 m3 ha-1, or 26.7% of average stand volume, with the highest intensity logging (69.3 Harvesting is widespread across the m3 ha-1) conducted by the agency responsible western two-thirds of Massachusetts and is for overseeing the largest conservation property expected to continue into the future. However, in southern New England. The impact of such in part because selective logging is typical in widespread, moderate intensity disturbance on the region and is difficult to document with forest management and conservation values and remote sensing, comprehensive spatial data on threats, including forest regeneration, harvesting activities are generally lacking, distribution and spread of invasive species, and particularly for the non-industrial private forest the integrity of forest, wildlife, and aquatic (NIPF) lands that comprise ~80% of forests in habitats, is almost completely unknown. We the state. Massachusetts Executive Office of have initiated a study to document forest Environmental Affairs (EOEA) has a unique, harvesting patterns across Massachusetts from spatially-explicit data set developed for 1984-2003 and to evaluate the influence of regulatory purposes that can be analyzed to harvesting on residual forest composition, tree provide important information for management regeneration, and invasive species distribution. and conservation planning. Analysis of a This summer we will begin extensive subset of these data from 19 towns in north- field work across central and western central Massachusetts suggests a surprisingly Massachusetts which, in combination with the

90 20-year, spatially-explicit, forest harvesting pine. Although red pine has been planted data set, will enable us to: (1) document forest widely in New England, very few sites are cutting patterns; (2) describe their spatial and known in Massachusetts where the species is quantitative characteristics with regards to thought to be native. One site investigated important forest resource values and physical, supports numerous individuals that are ~180- cultural, and environmental factors; and (3) 220 years old, with a few older stems. Whereas evaluate the influence of harvesting activity on some stands are apparently uneven-aged and residual stand composition, forest regeneration, have relatively abundant saplings or seedlings, invasive species distribution, and vegetation others lack any recent red pine regeneration. structure and composition. This study is a Charcoal or scarring is evident in each of the collaborative effort with The Nature red pine sites visited thus far, suggesting that Conservancy and results from this study will fire has strongly influenced the occurrence and help inform regional conservation efforts. In dynamics of these sites. addition, information that we gather will allow MA Department of Conservation and Recreation (DCR) staff to assess regional forest Woody Species Phenology, Prospect Hill management concerns (i.e., high grading and Tract, Harvard Forest - 2003 invasive species) and will directly aid statewide Forest Certification and Ecoregional planning J. O'Keefe efforts. 2003 was the fourteenth year in our ongoing investigation of the timing of woody Vegetation and Disturbance History of vegetation development during the growing Ridgetop Pitch Pine and Red Pine season. However in 2002 the scope of the Communities in Southern New England. study was changed significantly. For the first twelve years we observed bud break, leaf G. Motzkin, D A. Orwig, and D.R. Foster development, flowering, and fruit development on three or more individuals of 33 woody Over the past decade, we have species at 3-7 day intervals from April through conducted a series of investigations of the June. These observations documented disturbance histories and dynamics of a wide substantial (up to three weeks difference) range of barrens vegetation on sand plains in interannual variation in the timing of spring the Connecticut Valley and in the coastal region development, but good relative consistency from Cape Cod to Long Island. In the current among species and among individuals within study, we extend these investigations to rocky species during these twelve years. Therefore, ridgetops that support pitch pine or native red starting in 2002 we maintained the same pine in southern New England. Despite strong observation schedule, but reduced the number similarities in vegetation between ridgetops and of species observed to eight, including red sand plains, it is likely that ridgetops differ maple (Acer rubrum), sugar maple (A. substantially from sand plains with respect to saccharum), striped maple (A. pensylvanicum), disturbance history and vegetation dynamics. yellow birch (Betula alleghaniensis), white ash During this past year, we sampled ridgetop (Fraxinus americana), witch hazel (Hamamelis pitch pine vegetation on summits in the Taconic virginiana), red oak (Quercus rubra), and white Mountains, where preliminary data suggest that oak (Q. alba). This subset of important, stands are uneven-aged, similar to our previous representative species should allow us to results from Mt. Everett. The oldest individual continue to characterize leaf development each ridgetop pitch pine that we have sampled to spring, and document interannual variability date exceeds 225 years of age, although most while reducing the resources required for the stems are substantially younger. study significantly. Weekly observations of We are currently analyzing data from leaf coloration and leaf fall began in September several ridgetop sites supporting native red and continued through leaf fall. All individuals

91 are located within 1.5 km of the Harvard Forest Scaling Forest Productivity Through Space headquarters at elevations between 335 and 365 and Time Using Hyperspectral Remote m, in habitats ranging from closed forest, Sensing and Ecosystem Modeling through forest-swamp margins, to dry, open fields. S. Ollinger, M-L. Smith, J. Jenkins, L. Plourde, The winter of 2002-2003 was much M. Martin, D. Hollinger and J. Aber colder than normal with near normal precipitation, which resulted in snow cover well Understanding patterns of productivity into April. Cool weather continued through the and carbon cycling in temperate forests is spring. By summer the pattern changed to important for a number of scientific and policy warm and moist, which continued into the fall. issues. Locally, estimates are needed to address The first frost at Harvard Forest didn’t occur land management issues ranging from timber until October 3rd, seven days later than the harvesting to preservation of ecosystem mean first frost date since 1990, but still eleven diversity. Globally, forests play an important days earlier than the first frost in the anomalous role in the earth’s carbon cycle and are believed fall of 2002. to represent an important sink for atmospheric For most species initial bud break in CO2. The importance of understanding 2003 was extremely late (Table 1/Fig. 1), variation through space and time stems from the putting 2003 in a group with 1992 and 1997 as need to scale site-level measurements to their the years with the latest leaf emergence during broader surrounding regions and to identify the fourteen years of observation. Leaf underlying mechanisms responsible for development then progressed rather steadily observed ecosystem behavior. We have been with 75% leaf development also occurring examining the degree to which canopy nitrogen among the group of very late years. chemistry can serve as an integrator of C flux Fall coloration and leaf fall in 2003 patterns in northern temperate forests. The were quite late, but still nearly a week ahead of functional basis for using foliar N as a scalar of the extremely late timing of these events in C uptake lies in the fact that the proteins 2002. Averaging the four species in Fig. 1, responsible for CO2 capture by leaves (e.g. 50% leaf fall occurred on October 20th, five rubisco) account for the majority of nitrogen in days earlier than in 2002, but still five days plant canopies. This and other linkages between later than the prior ten-year mean and even with terrestrial C and N cycles has motivated several the prior latest year (1999). The extreme new advancements in the ability to detect lateness observed in 2002 expanded the canopy nitrogen using hyperspectral remote variability observed in leaf senescence sensing. significantly, so that it more closely resembled At several sites across New England, the variability observed in leaf emergence over including the Howland Forest in Maine, The the course of this study, and began to call into Bartlett Experimental Forest in New Hampshire question our previous assumption of and the Harvard Forest in Massachusetts, considerably less variability in the timing of fall efforts to map canopy N using spectral data events. These observations again point out the from NASA’s AVIRIS and Hyperion need for long-term data sets and emphasize the instruments have been coordinated with plot importance of temperature in regulating these level measurements of stand and canopy events. properties. At Bartlett, mapped estimates of canopy N concentrations were used to drive the PnET ecosystem model, resulting in prediction accuracy that was considerably improved over previously-available methods and revealing environmental controls related to climate, land

92 Table 1. Estimated mean leaf development dates (month-day) for individuals of six representative species over twelve years (IBB = initial bud break, 75% = 75% leaf development).

Quercus rubra (n=4) Acer rubrum (n=5) Betual allegheniensis (n=3)

IBB 75% IBB 75% IBB 75%

1990 127 (5/7) 166 (6/15) 121 (5/1) 164 (6/13) 122 (5/12) 155 (6/4) 1991 128 (5/8) 143 (5/23) 123 (5/3) 142 (5/22) 117 (4/27) 141 (5/21) 1992 135 (5/14) 163 (6/11) 133 (5/12) 170 (6/18) 132 (5/11) 164 (6/12) 1993 122 (5/2) 153 (6/2) 118 (4/28) 154 (6/3) 113 (4/23) 136 (5/16) 1994 129 (5/9) 154 (6/3) 124 (5/4) 151 (5/31) 122 (5/2) 147 (5/27) 1995 132 (5/12) 150 (5/30) 129 (5/9) 148 (5/28) 126 (5/6) 144 (5/24) 1996 133 (5/12) 151 (5/30) 121 (4/30) 150 (5/29) 118 (4/27) 145 (5/24) 1997 136 (5/16) 158 (6/7) 133 (5/13) 154 (6/3) 134 (5/14) 153 (6/2) 1998 123 (5/3) 142 (5/22) 120 (4/30) 140 (5/20) 121 (5/1) 138 (5/18) 1999 126 (5/6) 148 (5/28) 126 (5/6) 146 (5/26) 127 (5/7) 141 (5/21) 2000 129 (5/8) 161 (6/9) 129 (5/8) 156 (6/4) 129 (5/8) 149 (5/28) 2001 122 (5/2) 149 (5/29) 123 (5/3) 145 (5/25) 123 (5/3) 142 (5/22) 2002 118 (4/28) 156 (6/5) 125 (5/5) 150 (5/30) 126 (5/6) 151 (5/31) 2003 136 (5/16) 160 (6/9) 132 (5/12) 158 (6/14) 133 (5/13) 155 (6/4)

Quercus alba (n=3) Hammamelis virginiana (n=3) Acer pensylvanicum (n=4)

IBB 75% IBB 75% IBB 75% 1990 132 (5/12) 163 (6/12) 124 (5/4) 163 (6/3) 119 (4/29) 155 (6/4) 1991 127 (5/7) 150 (5/30) 116 (4/26) 144 (5/24) 118 (4/28) 141 (5/21) 1992 138 (5/17) 158 (6/6) 132 (5/11) 168 (6/16) 125 (5/4) 159 (6/7) 1993 124 (5/4) 150 (5/30) 121 (5/1) 149 (5/29) 121 (5/1) 144 (5/24) 1994 134 (5/14) 160 (6/9) 126 (5/6) 148 (5/28) 128 (5/8) 151 (5/31) 1995 135 (5/15) 157 (6/6) 127 (5/7) 148 (5/28) 127 (5/7) 148 (5/28) 1996 139 (5/18) 159(6/7) 123 (5/2) 150 (5/29) 130 (5/9) 151 (5/30) 1997 146 (5/26) 164 (6/13) 130 (5/10) 154 (6/3) 133 (5/13) 153 (6/2) 1998 126 (5/6) 145 (5/25) 113 (4/23) 139 (5/19) 118 (4/29) 142 (5/22) 1999 132 (5/12) 155 (6/3) 122 (5/2) 142 (5/22) 125 (5/5) 146 (5/26) 2000 132 (5/11) 162 (6/10) 126 (5/5) 151 (5/30) 127 (5/6) 155 (6/3) 2001 124 (5/4) 162 (6/11) 122 (5/2) 143 (5/23) 125 (5/5) 149 (5/29) 2002 132 (5/12) (158 (6/7) 109 (4/19) 152 (6/1) 121 (5/1) 152 (6/1) 2003 142 (5/22) 166 (6/15) 128 (5/8 156 (6/5) 132 (5/12) 156 (6/5)

J. O’Keefe

93 50% BUD BREAK(bottom), 75% LEAF SIZE(middle), 50% LEAF FALL(top)

330

310

290

270 Acer rubrum

250 Betula alleghaniensis

230 Quercus alba

210 Quercus rubra Julian Date

190

170

150

130

110

0 1 2 3 4 5 6 7 8 9 0 1 2 3 9 9 9 9 0 99 99 99 99 99 99 00 00 00 1 19 1 1 19 1 19 1 1 19 2 2 20 2 Year

Figure 1 J. Okeefe

94 use and topography (Fig. 1). Model predictions damage in 1997. Following this snowstorm, a and plot-level measurements both indicated new threat was discovered on the downed strong relationships between whole-canopy N branches, the introduced insect pest, the concentrations and measured aboveground hemlock woolly adelgid (HWA). Since the productivity (ANPP; Fig. 2). discovery of HWA at the Arboretum, an action Much of our present understanding of committee was formed to develop plans for temporal patterns in forest C dynamics derives managing Hemlock Hill to meet the new threat. from data collected using the eddy covariance Over 1800 hemlock trees were tagged, method. At the Harvard Forest EMS tower, measured for diameter, assigned a crown health temporal trends in gross primary productivity rating, and mapped with GPS coordinates. include an upward trend over the period from Various chemical and biological control 1992-2001, interrupted by a decline in 1998 (S. treatments were attempted to control the spread Urbansky and S. Wofsy; Fig. 3a, solid black of HWA at the arboretum, with mixed success. line). This pattern is of interest for a variety of From 1998 to 2002, 263 trees have died or were reasons, but few explanations have been removed due to poor health. Of the remaining brought forward. Running the PnET-Day 1600+ trees, 70% are rated as being in poor canopy photosynthesis model over this time condition. Since this is a heavily used portion period using measured daily climate inputs and of the Arboretum, which is part of the Boston a constant foliar nitrogen value produced a Parks Department, the decision has been made roughly 10 % underestimate and did not track to remove many of the dead and dying trees to these observed temporal trends (Fig. 3a, dashed reduce risks posed to the general public by gray line). falling limbs. This unfortunate turn of events In a second set of model runs, provides us with an unusual opportunity to interannual variation in canopy N was included examine the environmental impacts of hemlock using data from the control plots of the nearby death and hemlock removal in an urban chronic N study (data courtesy of A. Magill and environment, including soil nutrient cycling, J. Aber). Interestingly, data for the dominant microclimate changes, and vegetation deciduous species—black oak and red oak— succession, especially the spread of invasive showed a mild upward trend in foliar N over species. During 2004, we will collect baseline time, similar to that in GPP, and produced soils and vegetation information in 6 plots on model predictions that agreed more strongly the hill. Hemlocks will be removed from 4 with measured flux data (Fig. 3b, gray line). plots in winter of 2005, and 2 will remain as The underlying causes of these patterns are still control plots. Slash in the cut plots will either unclear, but these results suggest that temporal be chipped and left on site or removed to see variation foliar N may help to explain the what impact it has on ecosystem and vegetation observed trends in carbon uptake. trajectories. Data from this project will provide a nice comparison to the rural cutting and girdling that will take place at HF next year (see Hemlock Woolly Adelgid at the Arnold Barker Plotkin, Ellison et al., this volume). Arboretum: Threats and Opportunities Simultaneously, we will be investigating the resistance of Chinese hemlock (Tsuga D.A. Orwig, P. Del Tredici, H. Lux, R. Schulhof chinensis) to HWA. This species, which was and D.R. Foster planted on Hemlock Hill in 1999, appears to be extremely resistant to HWA and may be useful Hemlock Hill at Harvard University’s Arnold in reforesting portions of the hill. Arboretum is located in Jamaica Plain and has long been considered a remnant of the forest primeval in the heart of Boston. Eastern hemlocks have dominated the flanks and crest of this hill for centuries, despite experiencing many past disturbances including cutting in the late 1700s and early 1800s, fire in 1932, hurricane damage in 1938, and heavy snow 95 Figure 1. Predicted net primary production for the Bartlett Experimental Forest in New Hampshire, generated by combining remotely-sensed estimates of canopy nitrogen with the PnET ecosystem model.

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Figure 2. Predicted and observed wood growth in relation to canopy N concentrations at the Bartlett Experimental Forest. Wood growth measurements are from multiple-year biomass increments. Foliar N data are from plot measurements and spectral calibration of image data from the Airborne Visible and InfraRed imaging Spectrometer (AVIRIS).

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a. 18 HF Tower PnET, Constant FolN 16

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Figure 3. Predicted and observed daily gross primary productivity (GPP) at the Harvard Forest flux tower (data courtesy of S. Urbansky and S. Wofsy). Predictions were generated with PnET-Day using daily meteorological inputs. Figure 3a shows model predictions using a constant foliar N value. Figure 3b shows model predictions using variable foliar N data from the HF chronic N addition control plots.

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Landscape Level Analyses of Hemlock stand densities varied from 225 - 2025 ha-1. Woolly Adelgid Outbreaks in Massachusetts Most stands were found on northern and western aspects with slopes of 20 - 30%. HWA D. Orwig and N. Povak* was found in close proximity (a few km) to VT, suggesting it is continuing to migrate Over the last 18 years, hemlock woolly unimpeded at the northern extent of its current adelgid (HWA) (Adelges tsugae), an introduced range. aphid-like insect from Asia, has expanded its HWA was present in almost 50% of the range from southern Connecticut to northern sampled stands, although overstory hemlock Massachusetts, causing widespread mortality mortality levels are still very low in most and decline of Tsuga canadensis (eastern stands. Only 5 stands had greater than 20% hemlock). Building on similar analyses in overstory hemlock mortality and 2 forests Connecticut, we have mapped the distribution located along the southern border had overstory of all T. canadensis stands (> 3 ha) prior to losses > 50%. Over half of the stands visited HWA infestation in a 4000 km2 transect had experienced some level of hemlock logging through Massachusetts to characterize the in the last 10 years. This information has been temporal and spatial patterns of damage incorporated into a GIS analysis of the generated by HWA since the time of its arrival landscape-level, biological, edaphic, and into the area in 1989. To date, over 5000 stands historical factors associated with the patterns of with > 10% hemlock have been mapped, HWA-induced hemlock damage. Potential representing over 86,000 ha, or 21% of the replacement species already present in the study area (Fig. 1). We began sampling in the canopy of many T. canadensis forests include NW corner of the region in the summer of 2002 Quercus rubra (red oak), Pinus strobus (white and have since sampled 79 stands to obtain pine), Betula lenta (black birch), and several information on forest structure, composition, Acer (maple) species. and crown vigor, site and edaphic We will continue to sample stands characteristics, potential replacement species, throughout this region in 2004 to examine the and the spatial pattern of HWA and associated relationship between site and stand canopy damage. Overstory T. canadensis characteristics and intensity of infestation and importance ranged from 24 – 92% and total extent of mortality that occurs.

Figure 1. Distribution of all mapped hemlock stands in central Massachusetts, with location of sampled forests.

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Community and Ecosystem Effects of HWA- consequences of an invasive pest on forests Induced Logging. dominated by eastern hemlock. J. of Biogeography 29: 1489-1503. D. Orwig, L. Pustell, S. Jefts and D.R. Foster

The recent unimpeded infestation of the Ecosystem Analyses of Hemlock Woolly hemlock woolly adelgid (HWA; Adelges tsugae Adelgid Outbreaks in Southern New Annand) across the northeastern U.S. has England created a situation in which large-scale hemlock decline and mortality is occurring. HWA has D. Orwig, S. Jefts, L. Pustell and D.R. Foster already infested over 40% of the towns in Massachusetts and, as a result, many In 1998 we began examining the landowners are choosing to pre-emptively response of ecosystem processes to the stress harvest their hemlock stands. Information from and mortality caused by the introduced hemlock timber harvesters, state agencies, and studies of woolly adelgid (HWA) in 8 sites in southern landscape patterns of hemlock decline in New England varying in HWA infestion level. southern New England indicate that the recent Over the last 5 years, chronic HWA infestations broad scale increase in logging associated with at most of these sites have led to deteriorating HWA is occurring with little ecological crowns and increases in forest floor light levels. assessment and in the absence of scientific In addition, these structural changes have led to background for conservationists, land lower soil surface moisture levels, higher soil managers, or policy makers. temperatures, and higher sub-surface moisture We are beginning a study that builds on levels. These microenvironmental changes, in previous work on hemlock logging (Kizlinski et combination with reduced uptake as trees al. 2002) and compares HWA impacts with deteriorate, have lead to attendant changes in N those of hemlock harvest on the magnitude and availability and cycling over time. Infested trajectory of community and ecosystem stands have consistently exhibited higher net dynamics. Twelve sites have been selected for nitrogen mineralization and nitrification rates, intensive study throughout central as well as higher nitrogen availability than Massachusetts on public and private lands uninfested or recently infested stands. Results where hemlocks have been recently harvested indicate that introduced pests and selective tree at varying intensities. At each site we will decline can rapidly and dramatically alter monitor: available soil nitrogen using semi- ecosystem processes, even prior to the onset of annual resin bags, soil mineralization and extensive tree mortality. In 2001, we began nitrification using in situ incubated soil cores, examining 2 additional stands that contain high and soil temperature with dataloggers overstory hemlock mortality and a dense black throughout the growing season. In addition, we birch understory (see Jefts and Orwig this will sample herb, shrub, and understory woody volume). We will continue to sample these vegetation dynamics. We will contrast the rate, stands and select a few additional sites (e.g., magnitude, and quality of community and uninfested controls and heavily infested stands ecosystem response to logging versus HWA with birch understories) as they deteriorate to and relate these to differences in site conditions, determine the extent to which changes in microenvironmental change, and disturbance overstory composition, microenvironment, and intensity. We hope to be able to make soil conditions produce fundamental changes in recommendations to landowners about the most the cycling of nitrogen. ecologically appropriate management practices for their hemlock stands.

Kizlinski, M.L., D.A. Orwig, R.C. Cobb, and D.R. Foster. 2002. Direct and indirect ecosystem

99 Late Holocene Vegetation Patterns of the glacial outwash, a substrate that favors pitch Coastal Region of Southern New England pine. Wildwood Lake is located on a moraine and New York within Long Island’s pine barrens region (Fig 1). Hardwood-dominated forest sites are W W. Oswald, D. R. Foster, and G. Motzkin characterized by high pollen percentages for oak (30-50%), beech (5-15%), hickory (5- Plant communities of the coastal region 10%), and/or maple (3-8%). Several of these of the northeastern United States, including sites are located on moraines (e.g. Deep, Sandy grasslands, shrublands, and pitch pine-oak Hill, Fresh RI, and Harlock), but others occur forests, are of great conservation interest on better-drained substrates (e.g. Jemima), because they provide habitats for numerous indicating that the composition of pre- uncommon and rare species and assemblages of settlement forests was not determined by plants and animals. To inform management edaphic conditions alone. The pollen records and conservation efforts, various approaches from several of the hardwood-dominated sites have been used to determine which factors exhibit a strong response to settlement, with influence the composition and distribution of large increases in the percentages of weedy and coastal ecosystems. In general, three factors are agricultural pollen types. In particular, Fresh thought to be responsible for the primary RI, Ice House, Jemima, Duarte, and No Bottom variations in vegetation: substrate, disturbance Pond have large compositional differences (e.g. wind, fire), and land-use history. To better between pre- and post-settlement samples, understand how these and other factors affect suggesting that these sites may have modern ecosystems, we examine experienced the greatest degree of forest paleoecological records from sites along the clearance. This interpretation is generally coast and on nearby islands from Cape Cod, consistent with maps of mid-19th century forest Massachusetts, to Long Island, New York (Fig. cover, as several of these sites have little nearby 1), and thus provide the first summary of late forest cover at that time (Fig. 1). Holocene vegetation change across this region. This comparison of late Holocene Pollen records are available from many pollen records from across the coastal region of coastal sites, including Cape Cod, Nantucket, southern New England and New York Martha’s Vineyard, Block Island, and Long reinforces the conclusion that plant community Island. These sites represent a range of modern patterns are strongly influenced by substrate plant communities, geographic settings, and land-use history. Future analyses will disturbance histories, and substrate types. We incorporate sedimentary charcoal records to compared a subset of the records to explore further explore spatial and temporal variations regional patterns of vegetation for the time in fire across this region. periods before and after European settlement, restricting the pre-settlement interval to 2500 years before present. Multivariate analysis of Contribution of Red Maple to Carbon the 14-site dataset using detrended Uptake in the Eddy-flux Tower Plot Forest correspondence analysis (Figs. 2 and 3) reveals N. Pederson, E. Hammond Pyle, A. Barker two general patterns: (1) compositional Plotkin, G. Jacoby and S. Wofsy variations in pre-settlement forests, and (2) varying impact of settlement-era forest Northern red oak (Quercus rubra L.) (NRO) clearance. and red maple (Acer rubrum L.) are the primary For the pre-settlement interval, sites contributors to annual carbon uptake of the generally can be assigned to either pine- or forest surrounding the eddy-flux tower at the hardwood-dominated forest types. Sites with Harvard Forest (HF). Both species were high pine pollen percentages (20-60%) are sampled to compare tree-ring and eddy-flux located on Cape Cod (Round, Eagle, Fresh MA, estimates of carbon uptake. NRO results were and Duck) and Long Island (Wildwood). The presented at last year’s symposium. (Pederson Cape Cod sites are located on coarse-textured

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Figure 1. Map of southern New England and New York showing study sites and surficial geology (top panel) and mid-19th century forest cover (bottom panel).

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Figure 2. Detrended correspondence analysis of pollen records from southern New England and New York. Closed and open symbols are centroids of pre- and post-settlement samples, respectively. Thick black lines = Cape Cod; thin black lines = islands; gray line = Long Island. Squares indicate sites located on glacial outwash deposits; circles indicate moraines and other substrates.

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102 400

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Figure 3. Detrended correspondence analysis taxon scores for pollen records from southern New England and New York.

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103 et al., 14th Annual Harvard Forest Ecology Symposium Abstracts, 2003). We focus on red maple this year Thirty-five correlated to February temperatures. Since previously tagged red maple were randomly NRO growth was also negatively impacted by selected and cored in the eddy-flux tower gypsy moth defoliation, it seems its dominant footprint (TP) and the Lyford Plot (LP) in July canopy position and relative insensitivity to 2003. Three cores/tree were collected. The radii winter temperatures versus red maple gives it a were cored approximately 1200 from each other competitive advantage. around the stem. Crossdating, a fundamental Comparison of NRO and red maple basal dendrochronolgical technique, was used to area increment curves, a proxy for biomass and develop a precisely dated annual time series of carbon uptake, indicate that at the tree scale, the growth. Crossdating is the process of contribution of red maple to forest carbon identifying unique sequences of ring patterns uptake is declining (Fig. 2). Because of their and characteristics among all core samples to large numbers (264 stems/ha vs. 124 stems/ha assign calendar dates to each ring. When done for NRO), however, red maple still contributes correctly this process creates a time series with significantly to stand level carbon uptake. In a dating error of +/- zero years. After contrast, NRO contributes a significant amount crossdating, annual ring widths were measured of carbon uptake primarily through higher to the nearest 0.001 mm. growth rates. Red maple chronology development This experimental research comparing revealed that some trees were capable of great tree-ring and eddy-flux estimates of carbon radial growth plasticity. For example, radius a uptake is in its final stages. NRO and red maple of tree E4_822 in the TP experienced a chronologies from the Lyford Pots will be used significant growth reduction from 1956-1971 to determine if the TP trees are a good while the other radii grew fairly normally (Fig. representation of growth at the HF. 1A). Radius a of tree 4309 in the LP Chronologies of eighteen NRO populations experienced a significant growth increase covering central New England and New York starting in the late-1980s while radius b State will be used to place the HF NRO in a continued to decline in radial increment (Fig. long-term and regional perspective. 1B). The plasticity suggests a survival strategy for red maple saplings that allows it to persist through years of poor growing conditions. Vegetation Control of Ecohydrologic Six of the 35 cored trees had very little Processes radial growth around their lower stem over the last 10-15 years (Figs. 1A, 2). Mensuration data N. Phillips, M. Daley, M. Friedl and G. supports these results. The largest growth Salvucci declines occurred after gypsy moth defoliation in 1981, which appears in the form of a white The dynamics of water storage and colored, narrow 1981 ring. The declines also depletion in trees occurs on timescales similar coincided with 6 years of August drought and to that of the characteristic response times of two cold winters during the early 1980s. From small watersheds. 1930-1994 red maple growth was strongly Our work at Harvard Forest seeks to correlated to increased August precipitation and understand how vegetation modulates prior-October through January temperatures. ecohydrologic function, such as stream The combination of these abiotic and biotic hydrographs. In our first summer of research events reduced red maple growth. we quantified hydraulic resistance to water flow Canopy position and climatic sensitivity and storage capacity in boles and branches of may explain differences in recent growth rates Paper Birch, Red Oak and Red Maple. We between NRO and red maple (Fig. 2). From applied step changes in light and vapor pressure 1930-1994 NRO was only weakly correlated to deficit to examine the time lags of water flux in August precipitation and prior October these tree species. These data provide a temperatures and significantly, but negatively diagnostic means of determining whole tree

104 time constants for water flow, which may in the established. In 2000 and 2003, coarse woody future be compared with stream flow time debris (CWD, all pieces of dead wood >7.5 cm constants. diameter, 1m length) were measured in a subset of plots. In 1999, the active forest management study was created by combining three of the Carbon Dynamics at Harvard Forest: original study plots with five additional plots. Results From the EMS Tower and Ecological Trees > 5cm dbh were banded, litter collection Plots established, and CWD surveys were implemented in 1999 (pre-harvest), 2001 and E. Hammond Pyle, C. M. Jones, S. Urbanski, K. 2003 (post-harvest.) The site was selectively McKain*, Z. Liscow*, V.Y. Chow, L. Hutyra, J. harvested in 2001, with immediate results Budney, J.W.Munger and S. Wofsy reported at the 2003 symposium (Hutyra et al.). For analysis of ecological data, we treat We use two approaches to characterize major pools separately, looking first at flux in carbon dynamics at Harvard Forest – live biomass (live trees), then in dead biomass continuous eddy-flux measurements and ground (CWD). Accrual of carbon in the pool of live based ecological plots. Eddy-flux biomass remains roughly consistent, year to measurements provide integrated whole system year, ranging from 1.03 to 1.6 MgC ha-1 (Fig. measurement of the interaction between forest 1a), and comprising 60-70% of NEE in most and atmosphere. The ecological measurements years. The episodic nature of mortality (Fig. provide context for eddy-flux measurements, 1a), however, leads to great variation in annual allowing us to partition carbon fluxes among storage of carbon in the live biomass pool alone major forest carbon pools. Additional (Fig. 1b). Movement of carbon in the pool of ecological measurements in an adjacent actively dead biomass is examined by comparing managed stand monitor the long and short-term repeated CWD surveys. In the undisturbed changes in the carbon cycle following a typical tower plots, carbon storage in CWD increased New England harvest. slightly (adding <1MgC/ha/yr) between 2000 Since the tower was established in and 2003 (Fig. 2), as would be expected for an 1991, continuous eddy-flux measurements of aggrading forest. For the logged plots, carbon dioxide at Harvard Forest indicate however, we found a loss of CWD between annual uptake varies year to year, with annual 2001 and 2003 (Fig. 2), reflecting the carbon sequestration ranging from 0.8 to 4.2 decomposition of heavy inputs during the MgC ha-1 (mean ~ 2.2 MgC ha-1 yr-1) from logging (~ 10 MgC/ha/year added between1999 1991 to 2002 (Table 1). The banner year of and 2001). 2001 (see Urbanski et al. abstract from 2003 In 2004, we plan to examine the spatial symposium) was followed by a return to long- context of our ecological measurements by re- term mean in 2002, with measured NEE (Net surveying plots implemented in 2000 by the Big Ecosystem Exchange) of -2.7. With 11+ years Foot project. A preliminary comparison of tree of eddy-covariance carbon exchange growth in the Big Foot plots and our plot measurements, an umambiguous secular trend reveals consistent discrepancy: Big Foot plots of increasing GEE (Gross Ecosystem show lower standing biomass, but similar Exchange) and R (respiration)has emerged. The annual increments (Fig. 3). This discrepancy long-term trend of GEE and R is about +2%/yr, might result from different human bias in which is roughly twice the rate of live biomass sampling methods – fixed radius versus accumulation. variable radius. We plan to address this by In 1993, ecological plots (n=34, 10m performing both methods on the same plots, radius) were established within the fetch of the and developing a relationship between the two EMS tower. In 1998, all trees greater than data sets. 10cm in diameter were outfitted with dendrometer bands for repeated measures of tree growth, and litter collections were

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Figure 1 - Annual increment of 3 radii per tree for a tree in the A) Tower Plot tree E4_822 and B) Lyford Plot tree 4309 showing temporal variations in growth aro und the lower stem.

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30

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Figure 2 – Average basal area increment curves for northern red oak (solid line) and red maple (dashed line) in the forest surrounding the eddy-flux tower plot at the HF.

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Table 1 : Net Ecosystem Exchange (NEE), Respiration (R), and Gross Ecosystem Exchange (GEE) for 11 years of study.

1992 1993 1994 1995 1995 1997 1998 1999 2000 2001 2002 Mean NEE -2.3 -1.8 -1.9 -2.6 -1.9 -2.0 -0.8 -2.3 -2.0 -4.2 -2.7 -2.2± 0.8 R 9.3 12 10.8 9.8 11.5 12.2 11 11.7 12.3 11.4 12.7 11.3±1.1 GEE -11.6 -13.6 -12.7 -12.4 -13.4 -14.2 -11.8 -14.0 -14.3 -15.7 -15.4 -13.6±1.3

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Figure 1: (a) Gross fluxes in live biomass at Harvard Forest. Above-ground woody increment (AGWI) remains relatively consistent, while mortality appears to be episodic. (b) Net fluxes in live biomass. Episodic nature of mortality leads to greater variation in net storage in live biomass.

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Figure 2: Gross and net fluxes in coarse woody debris (CWD) in undisturbed (“Old 40”) and selectively logged (“Cut site”) plots, as estimated by repeated CWD surveys. “Additions” reflect pieces added between repeated surveys. “Decomposition” reflects pieces that disappeared between surveys. “Fragmentation” reflects reduction of size of remaining pieces.

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Figure 3: Comparison of our tower plots and big foot plots in years 2000 and 2001. Mean standing biomass for tower plots = 108 MgC/ha. Mean standing biomass for Big Foot plots = 71 MgC/ha.

E. Hammond Pyle, et. al.

110 Red Maple Re-Visited A Cross-site Study on the Effects of Experimental N Additions on Fine Root F. E. Rockwell Biomass, N Concentration and Total Soil Respiration The invasion of the understories of oak stands by red maple (Acer rubrum) over the last L.E. Rustad, I.J. Fernandez, S. McNulty, A. half century has received considerable attention Magill, J.D. Aber and the NERC N Network from forest ecologists. However, the significance of red maple’s understory Elevated atmospheric N deposition dominance for future canopy composition, or continues to be an environmental concern in whether in the absence of a stand-replacing many parts of the industrialized world. disturbance red maple will replace red oak Considerable research has addressed the (Quercus rubra) in the canopy as a late potential consequences of elevated N deposition successional dominant, remains a subject of for forested ecosystems, with significant debate. Previous research has interpreted advances in our understanding of the response individual tree records from permanent plots at of the aboveground plant community, soils, and the Harvard Forest in Petersham, surface waters to this non-point source Massachusettes, and Black Rock Forest in pollutant. In contrast, much less is known Nyack, New York, as supporting a hypothesis about the response of the belowground of eventual red maple dominance of these ecosystem, particularly fine roots, to elevated N stands. In this study, an additional 30 years of deposition. In order to address this information growth and mortality in these plots was gap, we initiated a cross-site study on the analyzed to evaluate an alternative hypothesis, response of fine roots to experimentally specifically that understory dominance by red elevated N deposition. The specific goals of maple need not translate into overstory this study are to (1) conduct a meta-analysis of dominance. Analysis of overstory and existing data on fine root response to elevated understory transition rates, growth, and N deposition from experimental sites in the mortality showed that red maple has northeastern US, eastern Canada, and northern successfully occupied canopy space released by Europe, and (2) use common protocols to the declines of Betula papyrifera, and Fraxinus directly measure the effect of N additions on americana. However, such gains in canopy the production, metabolism, and turnover of representation have been offset by high rates of fine roots at three internationally recognized mortality, or overtopping associated with forest ecosystem study sites in the northeastern continued crown expansion by red oak. In U.S.: the Harvard Forest in MA, the Bear addition, the increasing representation of late Brook Watershed in Maine (BBWM), and successional species such as Fagus grandifolia, Mount Ascutney in VT. as well as the increasing importance of Betula Data from 17 experiments at 15 sites alleghaniensis and B. lenta, suggests that, in across North America and Europe were used in natural stands, by the time oak crown stop re- the meta-analysis. Results showed that, across iterating these species may be in a position to all sites, N additions: replace much of the individual oak mortality that occurs. Ecophysiological mechanisms that (1) significantly decreased O horizon and might explain red maples ubiquity in the upper mineral soil fine root biomass understory, but apparent inability to compete by a mean of 43% and 17%, with red oak once in the canopy, are discussed. respectively, This study was based on research (2) increased O horizon and upper conducted at TS-1 (as well as data from the mineral soil fine root N Harvard Forest Archives) with Audrey Barker concentrations by a mean of 6% and Plotkin’s guidance in the spring and fall of 17%, respectively, and 2003. (3) decreased total soil respiration rates by a mean of 11%.

111 Preliminary data from the field study mineral soil horizons were logged at the same showed similar trends at the three experimental half-hourly temporal frequency as soil sites in the northeastern US, with a general respiration measurements. decline in O horizon fine root biomass, an The daily and seasonal trends and increase in O horizon fine root N concentration, effects of synoptic weather patterns are evident and either no change or decrease in total soil in the soil respiration measurements (Fig. 1a). respiration (Fig. 1). Diurnal variations were observed most days Results from both the meta-analysis (Fig. 1e). The seasonal trend is a general and initial year of the field study suggest that increasing rate of respiration over the course of elevated N inputs decrease fine root biomass, the summer as soil temperatures warm (Fig. 1c) increase fine root N concentrations, and and then decline into the fall with declining soil decrease soil respiration. These results are temperatures. The effects of synoptic weather consistent with the hypothesis that elevated N patterns appear immediately following deposition decreases C allocation to fine roots. precipitation and persist for several days, Other components of this research will evaluate depending on the amount of precipitation. the effects of N deposition on fine root life span Periods of several days without rain cause and chemistry, and will attempt to separate the drying of the O horizon and significant effects of elevated N inputs on root versus decreases in soil respiration. microbial respiration. Coherence analysis was preformed to investigate the relationship between soil respiration and soil temperature and water Coherence Analysis of High Frequency Soil content at differing temporal frequencies from Respiration, Temperature and Moisture the spring through fall period of 2003 (Fig. 2). Measurements A strong coherence of soil respiration and soil temperature occurs at a one-day interval, K. Savage, E.A. Davidson and D. Hollinger representing the diurnal trend. Coherence with temperature is also important for synoptic Temporal variation of soil respiration is weather patterns at 11-14 days and seasonal largely controlled by soil temperature and patterns at >90 days. Soil respiration shows a moisture. Temperature predominately strong coherence with the litter layer and influences the diurnal and seasonal trends in mineral soil water content at about 4 days and soil respiration, whereas soil moisture plays a at 7-14 days, which corresponds with common significant role in seasonal and interannual intervals between precipitation events and variations. Our previous studies have also wetting and drying cycles of the O horizon and shown that soil respiration responds rapidly to mineral soil. By understanding sources of precipitation events and that the magnitude and variation at diurnal, synoptic, and seasonal duration of response is dependent on many temporal scales, we can improve our empirical factors, such as length of dry period preceding models and our conceptual understanding of the precipitation, and the magnitude and duration of factors controlling variation in soil respiration. the precipitation event. In order to tease out these frequency relationships, high temporal frequency soil respiration measurements with corresponding temperature and moisture measurements are necessary. We installed an automated system for measuring soil respiration at a well-drained upland site approximately 150m SW of the EMS tower. Six automated chambers made half–hourly measurements between April 30th through November 28th, 2003. Soil temperature at 10cm depth and water contents in the leaf litter layer, F horizon and

112

Figure. 1. Mean (a) O horizon live fine root (<1mm) biomass, (b) O horizon live fine root (< 1mm) N concentration, and (c) total soil respiration at the BBWM Softwood and Hardwood (BBWM_SW and BBWM_HW) stands, the Mt. Ascutney (ASC) plots, and the Harvard Forest Hardwood (HAR_HW) and Pine (HAR_P) plots. Bars with different letters indicate significant differences between the treatment means within a site at the 0.05 level. Bars with ‘*’ indicate an overall difference between the treatment means within a site at the 0.05 level, without specific pairwise differences.

L. Rustad, et al.

113 K. Sav ( vol Fi H gure 1 ar um

v Soil Efflux a et age rd Hourly Precipitation Gravimetric -2 -1 ri (mg C m hr ) Fo Water Content a) m c wat 100 200 300 400 500 600

, et (mm) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 10 20 30 40 0 0 r e al. ean st) e d) b) 120 c) a) r c , e)so 125 (n ont 130 =6

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ure at 235 i ur 240 n

a 245 1 l t 250 0 r en

c 255 n m d. t 260 en dept 265

t in Soil Efflux 270 -2 -1

h an (mg C m hr )

t 275 100 h

280 20 40 60 80 e litterlayeran 0 d 285 123 h 290 e) o

u 295 r 124 l

y 300 p Fh l

305 e a r eci f

310 125 l o i r tte

315 i z d F pi on 320 r W t a 126 t h

325 C i o on 330 rizon 0.1 0.2 0.3 0.4 0 4 8 12 16 20 24 ,

c) Soil Temp Volumetric Water Content

May 18-Sept 22, 2003 7-8 days 11-14 days 127 days 1 day 4 days 1.0

0.8

0.6

oherence 0.4 C

0.2

0.0 1 10 100

Log(days) Soil T Oi WC 4.5cm VSM

Figure 2: Coherence analysis of mean flux and soil temperature (Soil T), leaf litter water content (Oi WC) and mineral soil water content at 4.5cm depth (4.5cm VSM).

K. Savage, et al..

115

Changes in Carbon Storage and Net Carbon Of the harvested wood, approximately Exchange After a Shelterwood Harvest at half went into paper products and half for Howland Forest, Maine longer-lived wood products (half-life of 3.5 and 45 y, respectively). Based on these N. Scott, E. Davidson, D. Hollinger, C. assumptions, and estimates of slash Rodrigues, J. Lee, H. Hughes, J. Walsh and P. decomposition (20, 7, 2, and 3.5 year half-lives Malerba for stumps/coarse roots, branches, foliage, and fine roots, respectively), we predict a much While many forests in the northeastern larger reduction in NEE (Fig. 2) than suggested US are actively sequestering carbon, little by our initial comparison of NEE in the control research has examined the direct effects of and harvested stands. This could result from forest management practices in this region on under-estimating carbon uptake by the trees carbon sequestration. This is a critical issue for after harvest, or over-estimating dead-wood the region, where a large proportion of forests decay. To better quantify carbon fluxes from are undergoing some form of management. dead-wood decay, we examined the relationship Will forest management prolong the capacity of between dead-wood respiration rates, forests to accumulate carbon, or perhaps reduce temperature, and moisture content. Both maximum potential carbon storage? At temperature and moisture content correlated Howland Forest in Maine, in collaboration with positively with respiration rates, but International Paper, we are using eddy temperature was important only when water covariance, biometric techniques and modeling content was >50% (Fig. 3). Below 50%, to evaluate changes in carbon storage following respiration from dead wood averaged 1.7 µgC a shelterwood cut that removed just under 30% g-1dw hr-1. Above 50% water content, dead- of aboveground biomass. Shelterwood cuts wood respiration was estimated using the have become increasingly popular in Maine, relationship between temperature and accounting for just over 25% of the harvest respiration rate (Fig. 3b). In conjunction with activity (in terms of land area) in 1999 (about annual temperature data, these results can be 60,000 ha). used to estimate CO2 production from dead- Prior to harvest, the stand contained wood decay. Better estimates of tree growth about 76 Mg C ha-1 (30 m2 ha-1 basal area) in are being obtained using a combination of above- and below-ground live biomass. forest inventory plots and dendrometer bands. Harvesting removed about 15 Mg C ha-1 (SEM=2.1), and created about 5.3 Mg C ha-1 (SEM=1.1) of aboveground and 5.2 Mg C ha-1 Temporal and Spatial Variation of (SEM=0.7) of root/stump detritus. Leaf-area Nearground Atmospheric CO2 in a index and litterfall declined by about 40% with Permanent Woodlot Site in Prospect Hill harvest. When compared to a nearby unharvested stand (with average net annual T. Sipe, J. Clowers*, A. Sanchez Sierra* and J. uptake of 1.7 Mg C ha-1 y-1), net ecosystem Vuong* exchange (NEE) declined following the harvest by about 18% (Fig. 1), which is less than We measured ambient CO2 expected based on reductions in basal area and concentrations in the herbaceous stratum during LAI and (expected) increased heterotrophic the first phase of a three-year study on the respiration resulting from slash decay. Both combined effects of nearground enriched CO2 daily uptake and nocturnal respiration declined (NEC) and sunflecks on photosynthesis by after harvest. Soil respiration declined slightly herbaceous and woody species. CO2 was but non-significantly with harvest; harvesting sampled simultaneously every 30 minutes at had little effect on soil moisture and two heights (10, 30 cm) each in 23 locations temperature. spaced regularly across a 30 x 50 m permanent plot in a mixed hardwood-hemlock forest. Fresh

116 samples were queued for analysis and stored in not measurable on most nights. Falling soil the sample tubes over a 3.5-minute period. temperatures reduced soil respiration and Samples were then transferred sequentially to eventually caused declines in ambient CO2 an infrared gas analyzer (LI-7000, Li-Cor, Inc.) during the early morning hours (1-6 am). through multiport switching valves and Although soil temperature rose throughout the measured in differential mode against CO2-free day, ambient CO2 did not track temperature in nitrogen gas bled through the reference cell. An midday and early afternoon due to increased entire measurement sequence required 11 wind and probably to photosynthesis in the minutes. Soil temperature (5 cm, thermistors) herbaceous stratum. CO2 began to build in the was measured at 8 of the 23 locations and early evening and increased for several hours windspeed (40 cm, cup anemometers) was after soil temperatures peaked. Though we were measured at 3 of these 8 to provide data on the not able to measure it, the subsidence of cooled primary factors controlling soil CO2 flux and air with comparatively low CO2 concentrations nearground mixing. Soil respiration rates were from the canopy toward the forest floor estimated by applying empirical relationships probably contributed to the decline in ambient for similar soils in Prospect Hill to the soil CO2 in the early morning hours. temperature data. The difference in CO2 between 10 and We tested the CO2 measurement system 30 cm averaged 20 ppm (range 4-70) across the by repeatedly sampling one intake tube 16 23 sample locations, and showed a modest times over a 2.2-min period during each 30-min exponential relationship to overall CO2 2 event across several 24-hour cycles. The 16 concentration (R = 0.74, N = 106). CO2 samples showed no trends across the 2.2 concentrations at the two heights were strongly minutes, suggesting that the pumping did not correlated across the 5-day run (R2 = 0.98, N = induce significant vertical mixing at the tube 106). Global spatial variation expressed as the inlets. The first sample showed a very high standard deviation across the 23 sampling correlation to the mean for all 16 samples (R2 = locations averaged 23 ppm and showed an 0.96, N = 106), and was thus a reliable measure exponential relationship to ambient CO2 for 2 2 of ambient CO2 at the time pumping was both 10 cm (R = 0.68, N = 106) and 30 cm (R initiated. The sampling error, calculated across = 0.62, N = 106). The two most divergent the 16 successive samples as the coefficient of sample locations differed by an average of 94 variation, averaged 0.75% (range 0.2 to 2.0%, ppm (range 21-306 ppm) at 30 cm. Horizontal N = 106) over a 405-706 ppm range of ambient variation expressed as the range across the 23 CO2. sample locations showed a fairly strong linear Ambient CO2 averaged 475 ppm (range relationship to the maximum vertical difference 356-1024) across the two heights, the 23 between 10 and 30 cm (R2 = 0.59, N = 106). sample locations, and all sampling events These results, plus prior work on during five successive 24-hour cycles (July 1- photosynthesis by several species, suggest there 5). Daytime (6 am-8 pm) values were is marked variation both horizontally and considerably lower (mean 447, range 356-829) vertically in nearground CO2 environments and than nighttime (8 pm-6 am) values (mean 511, that the enrichment is of sufficient magnitude to range 394-1024). The diurnal cycle was substantially affect diurnal carbon gain by pronounced, with peaks near midnight and plants in the herbaceous stratum. troughs near solar noon on most days (Fig. 1). The cycle was phase-shifted with soil temperature by about 7 hours, so ambient CO2 correlated poorly (R2 = 0.12) with estimated soil respiration. The correlation was improved only marginally when samples were divided between daytime (R2 = 0.29) and nighttime hours (R2 = 0.39). Windspeeds ranged as high as 3.0 m/s, peaked in early afternoon, and were

117

Figure 1. Comparison of net CO uptake between eddy covariance towers in the control and harvested stands Figure 1. Comparison of n2e t CO2 uptake between eddy covariance towers in the control botanhd pre ha-harvrevsetsetd an sdta postnds- habortvhest pre-h. Difaferervenscest an ind t hpoe slsto-phearvs oef stht.e s Die relffaetrieonsnchiesps i ns utghgees stl oanp es18 %of rethdesuceti on in NEE following harvest. relationships suggest an 18% reduction in NEE following harvest.

Figure 2. Predicted changes in net carbon storage for 30 years after shelterwood harvest. E Net C storage including slash and wood product decay. D Net C storage including slash only. ? Net C storage not including either slash or wood products. Negative sign indicates net C loss.

N. Scott, et al.

118 Figure 3. Effects of temperature on dead-wood respiration rates when water content is <50% (a) and >50% (b).

Scott, et al.

650 300

600 275

550 250

500 225 CO2 (ppm) 450 200 or Windspeed (cm/s)

400 175 Predicted Soil Resp (mg C/m2/hr)

350 150 12 24 36 48 60 72 84 96 108 120 132 144 156 168 Time (hrs) CO2 6 am-8 pm Predicted Soil Resp Windspeed

Figure 1. Diurnal patterns of nearground atmospheric CO2, windspeed, and soil respiration estimated from soil temperature measurements over July 1-5, 2003 in a mixed hardwood- hemlock site in Prospect Hill. CO2 was sampled simultaneously every 30 minutes at 10 and 30 cm above ground at 23 locations regularly spaced across a 30 m x 50 m grid. Soil temperature and windspeeds were measured continuously at 8 and 3 of the locations, respectively. CO2 and windspeed data are smoothed (n = 7).

T. Sipe, et el.

119 Microbial Responses to Soil Warming the control for a majority of the substrates; however, this could be largely attributed to H. Smith, S.D. Frey, M. Knorr, H. Lux, and J. lower microbial biomass with heating. To Melillo normalize the data for differences in microbial biomass, the response for each substrate was During fall 2003 we collected soil cores divided by the average response for each (2.5 cm diam) from the control, disturbance treatment-replicate. Principal components control, and heated plots (n = 6) at the Prospect analysis indicated that normalized patterns of Hill soil warming experiment to examine the substrate utilization were significantly different effects of soil warming on the active biomass between treatments for the mineral soil, but not and functional capacity of the soil microbial the O-horizon material (Fig. 1). The mineral community. Each core was divided into O- soil data separated along the first principal horizon material (depth varied) and the top 10 component which explained 66% of the cm of mineral soil. Total physiologically active variation in the data. For the majority of microbial biomass was determined by substrate- substrates, the heated soils exhibited lower induced respiration. Catabolic response relative utilization compared to the control. profiles were obtained by measuring the short- However, six substrates were utilized to a term respiration responses to 25 substrates. relatively greater degree in the heated plots. This approach provides a fingerprint of the Taken as a whole, the catabolic response profile functional potential of the microbial data indicate that there was differential use of community. The substrates consisted of two specific substrates in heated soils. Microbial carbohydrates (glucose, mannose), two amines community composition and soil conditions (D-glucosamine, L-glutamine), six amino acids interact to determine substrate use patterns, (L-arginine, L-asparagine, L-glutamic acid, L- making it difficult to discern whether changes histidine, L-lysine, L-serine), and 15 carboxylic in catabolic response profiles are indicative of a acids (L-ascorbic acid, citric acid, fumaric acid, change in species composition or a change in gluconic acid, α-ketobutyric acid, α- microbial function in response to altered soil ketoglutaric acid, α-ketovaleric acid, DL-malic conditions. acid, malonic acid, pantothenic acid, quinic acid, succinic acid, tartaric acid, uric acid, urocanic acid). We also measured several soil Forecasting Stream Ecosystem Responses to organic matter fractions in the mineral soil, a Regional Landscape Disturbance: Indirect including total C and N, particulate organic Ecological Consequences of the Removal of matter C and N, and labile C. We found no Eastern Hemlock from New England Forests differences between the control and disturbance control plots for any of our measured W. Sobczak and B. Colburn parameters thus only show the data for the control and heated plots here. The question of how organic matter Active microbial biomass was 26% and moves from terrestrial to aquatic ecosystems 44% lower in the heated compared to control and within aquatic food webs is of fundamental plots for the O-horizon and mineral soil, importance to ecology. Knowledge of respectively. Lower biomass in the mineral soil mechanisms that control magnitudes and paths of heated plots was concomitant with of organic matter flux translates directly into significantly less labile C and a trend, though better ways to manage and restore aquatic food not significant, toward lower total and webs and ecosystem health. Such knowledge is particulate organic matter C contents (Table 1). of basic importance because it helps ecologists We observed a significant effect of warming on understand how seemingly diverse ecosystems the overall respiratory response following are closely connected and how perturbation addition to soil of 25 organic substrates. The within one ecosystem or habitat can alter microbial communities in the heated plots ecological functions and communities in exhibited a reduced response in comparison to adjacent or distant ecosystems or habitats.

120 Table 1. Carbon pools isolated from mineral soil collected from control, disturbance control, and heated plots at Harvard Forest Soil Warming Studya.

Treatment Total soil C POM- Labile b C C -1 ------µg C g soil------Control 4840 1140 537 (48) (710) (87) Heated 4490 963 365 (38) (117) (75) aValues represent the mean of six replicates ± one standard error. bPOM = Particulate organic matter

0.8

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0.4 Heated soil 0.2

Control O-horizon 0.0 2

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-0.4 Control soil

-0.6

-0.8

-1.0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 PC1 Figure 2. Principal components analysis of the catabolic response profiles for soil collected from control and heated plots.

H. Smith, et al

Eastern hemlock dominates many New England into New England and subsequent loss of forests and stream-side riparian areas, thus eastern hemlock from New England forests will influencing the supply of detritus and result in an array of ecological consequences. availability of light to many regional streams. Terrestrial ecosystem responses are just now Regional declines of hemlock have been being documented, yet aquatic ecosystem documented following the invasion of the responses to regional changes in riparian forest hemlock woolly adelgid, an exotic forest pest. composition are less certain. The proposed The continued expansion of the adelgid's range research aims to understand how the ecology

121 and biogeochemistry of the region's stream outermost (youngest) and innermost (oldest) ecosystems will be altered as riparian forests sapwood following equilibration to four change. We plan to examine (with colleagues) combinations of O2 and CO2 (shown changes in 1) stream hydrologic and thermal respectively, with mole fraction represented as regimes, 2) stream light regimes and primary a percent): 10% + 0%, 10% + 10%, 5% + 0%, production, 3) quantity and quality of organic 5% + 10%. In general, inhibition by reduced matter inputs, 4) microbial metabolism and O2 was far greater than inhibition by elevated downstream organic matter fluxes, and 5) CO2. All species showed reduced respiration at macroinvertebrate biomass and functional low O2 (average inhibition across species was feeding groups. Study areas will be streams just 25%), whereas only two species showed dominated by hemlock or hardwood, including inhibition by high CO2. In these cases, there former hemlock streams where hemlock has was a significant interaction between the gases been killed by the hemlock woolly adelgid. such that inhibition by CO2 was reduced at low O2. The effect of gas treatment was the same for both old and young sapwood. Our results Heartwood Formation in Forest Trees: suggest that gas concentrations within stems are Parenchyma Cell Death as a Driver of unlikely to play a role in the transition from Sapwood Senescence sapwood to heartwood. Instead, our work on the diversity of patterns of parenchyma cell R. Spicer and N.M. Holbrook death, as well as changes in nuclear morphology and cellular ultrastructure during The amount of sapwood maintained by this transition, suggest that this is a form of a tree affects carbon balance at a range of programmed cell death and should be viewed as scales, from the individual tree to the stand and an active stage in development. ecosystem. Sapwood functions in both water transport and carbohydrate storage in tree stems, and is ultimately converted to heartwood Long-Term Trends in Soil CH4 Consumption through the death of xylem parenchyma cells. at the Harvard Forest Chronic Nitrogen Heartwood then ceases to be physiologically Addition Experiment: Implications for the active - it no longer conducts water, and does Future Growth in Atmospheric CH4. not contribute to any respiratory gas exchange because it contains no living cells. But what P.A. Steudler, A.K. Chan, J.D. Aber, J. actually causes the death of xylem parenchyma Gulledge, C. Cavanaugh and J.M. Melillo cells is not known. Recent work demonstrating the role of transpiration in the supply of oxygen For the past 15 years we have been to internal stem tissue has raised the possibility conducting a field experiment designed to that anoxia may be responsible for cell death, examine the short- and long-term effects of whereas others have proposed that a build-up of chronic N additions to temperate forests on a respiratory carbon dioxide may be involved. number of biogeochemical processes including Instead, we have found that parenchyma cell soil CH4 consumption. The N additions were respiration is only slightly inhibited at the begun in 1988 in a 50+ year-old mixed reduced oxygen levels found within stems, and hardwood stand and a 70+ year-old red pine is also surprisingly robust to high levels of plantation. Nitrogen was applied as NH4NO3 at carbon dioxide. Species studied this summer at annual rates of 0, 50 and 150 kg N/ha over the Harvard Forest, with the help of REU student six- month growing season. Forests in this Teresa Abbott, included two conifers (Tsuga region receive about 8 kg N/ha/yr from dry and canadensis, Pinus strobus), two ring-porous wet deposition. During the first year of angiosperms (Quercus rubra, Fraxinus treatment we observed an immediate decrease americana) and one diffuse-porous angiosperm in the rate of soil consumption of atmospheric (Acer rubrum). Respiration rates were CH4 of about 23% in all of the amended plots measured for fresh xylem tissue from the compared to the controls. Over the next four

122 years the overall decrease in consumption Because the effects of global change on stabilized at about 36% and 62% in the weedy and invasive species raise ecological and hardwood and pine high N plots, respectively. socioeconomic concerns, we investigated how We re-measured the consumption rates CO2-enriched environments would influence at these sites in 2003, after 15 years N addition. light competition in the allergenic species, Results indicate that consumption rates have common ragweed (Ambrosia artemisiifolia). not remained constant at the levels measured in We grew competing stands at either ambient 1993, but have continued to decrease (360 ppm) or twice ambient (720 ppm) levels of dramatically in all treatments. The greatest atmospheric CO2 in an open-top chamber change was in the high N pine plot where the experiment (Fig. 1). We measured variance in consumption rate was reduced by 83%, while size, architecture, and photosynthetic rates the rate in the low N plot was reduced by 56%. between subordinate and dominant (small and The hardwood plots showed a similar pattern big) individuals, and generated vertical light with a reduction in the rates in the high and low profiles for each competing stand in the two N plots by 66% and 40%, respectively. treatments. Our findings on the long-term effect of The coefficient of variation (CV) was N amendments on the rate of CH4 consumption used to measure size inequalities among by temperate forest soils are consistent with competing plants. We found that elevated CO2 measurements in other forests in the United reduced the CV in plant size (Fig. 2). Thus States and Europe that have received moderate there were smaller proportional differences to high N deposition rates for decades. between dominants and subordinate plants at These results have important long-term high levels of CO2. We also found more implications for the CH4 consumption capacity positive relationships between total biomass of temperate forest soils. It appears that even and shoot biomass inequalities at ambient levels moderate levels of chronic N deposition may compared to enriched CO2 levels. In other diminish the potential for these soils to slow the words, larger plants showed proportionally less future growth in atmospheric CH4. advantage relative to small plants in enriched CO2 stands. Plants grown at high CO2 also grew taller and had proportionally greater upper Elevated CO2 Allows Smaller Plants to stem biomass than those in ambient conditions, “Catch Up” to Dominants in Competing which corresponded to decreasing light levels Stands of Common Ragweed (Ambrosia in the enriched treatments (Figs. 3 and 4). artemisiifolia) Finally, photosynthetic gains by larger plants were less pronounced in elevated- compared to K A. Stinson and F A. Bazzaz ambient-grown plants, but only in the upper canopy leaves (Fig. 5). The predicted doubling of atmospheric We conclude that physiological and carbon dioxide over the next century is likely to developmental stimulation in the growth of affect population, community and ecosystem subordinate plants allows smaller individuals to processes by altering competition for resources "catch up" to larger individuals in high CO2 within and among plant species. Asymmetric environments, leading to a reduction in competition for light can arise when larger dominant-subordinate size structures. This is plants progressively pre-empt greater quantities the first study to provide a comprehensive of light per unit size than smaller ones, thereby analysis of CO2-induced effects on biomass further suppressing subordinate individuals and allocation and photosynthesis in competing leading to greater size inequalities. Growth plant populations. Both architectural and stimulation by elevated atmospheric CO2 may physiological mechanisms lead to the reduced either mitigate or exacerbate light competition, size asymmetry in competing stands of this depending upon the developmental and allergenic pest species. Hence, these architectural responses of small and large mechanisms are likely to affect the outcome of plants.

123 competition, population densities, and human sunny habitat also outperform those from health in an enriched CO2 world. shaded habitat, but have equally poor reproductive success when grown together in the shade (Fig. 3b). Thus, the invasion process The Impact of Garlic Mustard (Alliaria appears to be driven by net influx of superior petiolata) on Native New England Forest seeds from high light habitats into shaded ones Communities and the Importance of Habitat at our study sites. It is possible that this process for Controlling its Spread. leads to an evolutionary “lag phase” which slows the successful invasion of forested sites K A. Stinson by shade-adapted genotypes. This study also includes a mapping Alliaria petiolata, or garlic mustard, project of garlic mustard populations in and threatens the native New England flora, around Harvard Forest (Fig. 4). Using these including spring ephemerals and regenerating maps, we are estimating dispersal into target tree seedlings (Fig. 1). Garlic mustard areas from local and more distant source establishes in two contrasting habitat types: populations and investigating relationships open sites such as roadsides, trails and forest between land use history, habitat quality, and edges receiving high light levels (sunny invasion success. This work will help explain habitat); and adjacent forest understory where how population dynamics and anthropogenic light availability is much lower (shaded disturbance facilitate habitat expansion in this habitat). We are conducting studies aimed at species. understanding 1) the impact of garlic mustard Our results to date demonstrate that on the native community structure of forests in small scale removals of garlic mustard from the New England, and 2) the influence of different forest understory can result in the restoration of habitats on the control and spread of this exotic native plant diversity within one growing plant. season. However, these removals are not likely We experimentally removed garlic to sufficiently control future invasions if high mustard from forested sites in western light populations are present. Roadside, forest Massachusetts in 2003. The Shannon Diversity edge, and other high light populations are Index was higher and native species were more probably important targets of eradication, even evenly distributed in experimental removal when management efforts seek to control plots compared to the control plots (Fig. 2). invasion in forested sites. Thus, garlic mustard reduces native plant diversity by dominating the herbaceous component of forest understory vegetation in Historic and Current Influences on Habitat these sites. Invasibility in a Mosaic Landscape: Cape Ongoing demographic observations and Cod National Seashore physiological experiments have further suggested that populations in high light sites B. Von Holle, D.R. Foster and G. Motzkin contribute to invasion into the forest understory in central Massachusetts. Despite its successful Effects of non-native species are a invasion into forested habitat elsewhere in the hazard to global biodiversity, second only to region, Harvard Forest populations demonstrate habitat destruction. For informed management lower reproductive output and population decisions, we must determine factors that growth in forested compared to sunny sites contribute to ecological resistance to biological (Fig. 3a). In addition, seedlings originating invasion. Habitat invasibility to plant invaders from parental plants in both habitats was investigated in the highly resistant Cape demonstrate higher photosynthetic rates, water Cod ecosystem through a spatially-explicit use efficiency, and seed production when study of historical disturbances and current experimentally planted into sunny conditions environmental and biotic properties of 20 x versus shade treatments. Plants originating in 20m field plots, randomly located across the

124

Figure 1. Atmospheric CO2 was maintained at either ambient (350 µL L-1) or elevated (720 µL L-1) levels using 16 open top chambers. Experimental stands were created by planting seedlings into evenly spaced positions on a grid. This design achieved natural field densities of approximately 102 plants/m2. Two replicate stands were grown in each chamber.

720 350

60 )

m 50 (c th g

n 40 e l

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c 30 n a r

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to 10 V C 0 19-Jul 30-Jul 7-Aug 18-Aug

Figure 2. Average stand-level coefficient of variation (CV) for ragweed plants based on total branch length, showing decline in variation among small and large plants at elevated CO2, and increased variation at ambient CO2. -1 -1 Light and dark colored bars represent elevated (720 µL L ) and ambient (360 µL L ) CO2 concentrations, respectively. Error bars represent ±1 standard error.

K. Stinson and F. Bazzaz

125

2000 1800 1600

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cm cm 5cm 5 0cm 5cm 0cm 5cm 0cm 5cm 0cm 0- 10 -1 -2 -2 -3 -3 -4 -4 -5 6- 11 16 21 26 31 36 41 46 Height (cm) 760ppm 360ppm

Figure 3. Light attenuation curves showing light availability through the canopy vertical profile for stands of -1 -1 ragweed. Open and closed symbols represent ambient (360 µL L ) and elevated (720 µL L ) CO2 concentrations, respectively. Data points symbolize mean PAR values for each treatment for three dates on which measurements were taken. Error bars represent ± 1 standard error.

720 350

0.60

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ass 0.40 m o i b f a

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em 0.20 st

ean

M 0.10

0.00 0-10 11-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90 91-100 Plant Section (cm)

Figure 4. Average above ground biomass for vertical sections of ragweed plants grown in ambient (360 µL L-1) -1 and elevated (720 µL L ) CO2 concentrations, represented by closed and open bars, respectively. Error bars represent ± 1 standard error.

K. Stinson and F. Bazzaz

126 14 720 12 350

R2 = 0.4537

) 10 c e /s 2 eaves /m l 2 8 y O C op l mo can

µ 6 2 per

ax ( R = 0.3922 m up -

p 4

2

0 0 10203040506070 total branch length (cm)

K. Stinson and F. Bazzaz

Figure 5. Relationships between maximum photosynthetic rates and total branch length (size) of ragweed plants. Larger plants have proportionally greater photosynthetic rates than smaller plants in ambient compared to elevated CO2 treatments. Open and closed symbols represent measurements for individual plants under ambient (360 µL -1 -1 L ) and elevated (360 µL L ) CO2 concentrations, respectively. (ANCOVA, p<0.01).

Figure 1. An invasive population of garlic mustard (Alliaria petiolata) in a forest site in Berkshire County, Massachusetts.

K. Stinson

127

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% high med low A. petiolata density

A. petiolata Sugar maple Ash cherry fine sedge aster violet

Figure 2. Native understory plants species are more evenly distributed in plots with experimentally reduced garlic mustard (A. petiolata) cover. The base of each bar represents percent A. petiolata cover. Other shades show key native forest species. These data correspond with significant increases in the Shannon Diversity Index.

a) b) Average rates of

reproduction 9.0 )

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g (

450 (

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S

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u 2.0 o

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t t 150 1.0 High light Low light 100 age N

er 50 v A 0

Figure 3. Reproductive success of plants from sunny and forest habitat a) in field populations at Harvard Forest, 2003; and b) when grown together in experimental light treatments. Fecundity is higher in open/sun sub- populations. Plants from sun (solid line) and shade (dashed line) sub-populations are equally less fecund in experimental low light treatments.

K. Stinson

128

Figure 4. Map of garlic mustard populations at Harvard Forest, showing relationship between presence of invasive populations and history of human disturbance (agricultural use). The mapping project will continue in 2004.

K. Stinson

landscape. These 352 plots were within natural conditions provided by the depauperate soils in areas, half within Cape Cod National Seashore, this area. In addition to this modeling study, MA. This region experienced intensive land two observational field studies were undertaken use during European settlement of the area, in the summer of 2003, to investigate further followed by large-scale reforestation in the last the determinants of invasibility of habitats in century and fire suppression in the last 60 years. Cape Cod National Seashore. Historic disturbances, current vegetation, Differential effects of natural and edaphic properties and other environmental anthropogenic disturbances on habitat conditions were determined for each plot using invisibility: Habitat invasibility to plant historic and field methods. These factors were invaders was investigated in the highly resistant assessed for their influence on exotic species Cape Cod ecosystem through a field survey of richness and cover with multiple linear native and nonindigenous plant species cover regressions and canonical correspondence along gradients of current natural and analyses. The most influential factors for non- anthropogenic disturbances. We surveyed 100 indigenous plant cover and richness were transects, each containing 3 field plots (20 x current soil nutrient conditions. While land use 20m) located perpendicular to and 2, 50 and history in Cape Cod National Seashore is a 100 meters from typical anthropogenic (roads, strong determinant of native community trails and parking lots) and natural (salt spray assemblages, this is not the case for non-native and wind) disturbances. Nonnative and native species in natural areas. The resistance of species richness and abundance values these natural areas may be due to the harsh decreased linearly with distance from current

129 anthropogenic disturbances. Nonnative species (nitrogen-fixing tree) into this upland forested richness and abundance values also decreased ecosystem resulted in ‘islands of invasion’ linearly with distance from natural within this otherwise resistant ecosystem. disturbances, however native species richness However, because of the significant natural and abundance showed a typical intermediate decline of this species in this ecosystem, we disturbance response, increasing curvilinearly recommend no active management of this with distance from coastal bluffs. While there species at this time. We will investigate the was a trend towards higher nonnative species relationship between native and nonnative richness in the anthropogenically-disturbed species richness with stand age to understand plots, this was statistically nonsignificant. the effect of succession on species dynamics in Native and nonnative species clearly have these stands. Additionally, we will undertake categorically different responses to natural spatially-explicit analyses of similarity values disturbances and similar responses to of nonnative species composition within Locust anthropogenic disturbances, which suggests that stands to understand if there is inter-patch these disturbance types mediate habitat movement of nonnative plant species. invasibility in distinctive ways. Facilitations between the introduced N- fixing tree, Robinia pseudoacacia, and Hurricane Damage Exerts Long-Term nonnative plant species in upland forests: Effects on Forest Development Black Locust, Robinia pseudoacacia, was identified as the nonindigneous species with the K. Wilson*, A. Barker Plotkin and D. R. Foster greatest impact on the native communities of Cape Cod National Seashore (CCNS). We Central to the Harvard Forest LTER is initiated this project to determine the impact of examination of natural disturbance and Black Locust on plant species distribution and anthropogenic stress. Hurricane blowdown is a to estimate the spread of this species within the major natural disturbance process in New National Seashore. We censused 20 x 20m England, and has been studied at Harvard plots for species cover and environmental Forest through large-scale manipulation, characteristics in the center of twenty historical reconstruction and modeling. randomly-selected Robinia pseudoacacia Permanent plot data allow us to expand our stands. Additionally, paired plots were understanding of long-term hurricane effects on surveyed under native overstory stands, forest dynamics; here, we use permanent plot comprised largely of Pitch Pine (Pinus rigida). data to illustrate the persistent effects of These native stands were located 20m from the hurricane damage 30-60 years after the great edge of the sampled Locust stand, and had hurricane of 1938. A 2.9 hectare hardwood similar land use histories. To determine the forest plot was established in 1969 at Harvard historical expansion of Black Locust, we Forest. All living and dead trees were censused digitized and georeferenced historical aerial in 1969, 1975, 1987-92 and 2001. Based on photographs of randomly-selected stands in distribution of windthrown stems and damage CCNS from 1970 to 2002. Nonnative plant boundaries delineated immediately after the species richness and abundance values were 1938 hurricane, the site was divided into severe statistically significantly higher within Robinia (91-100% damage, 0.3 ha), moderate (51-75% stands than within the paired native stands (Fig. damage, 0.9 ha) and low (11-25% damage, 1.7 1). Robinia stand area significantly decreased ha) damage areas. over time, however this decrease depended Intensity of hurricane damage upon the distance of the stand from roads. continues to shape forest development, 30-60 Robinia stands closer to roads experienced the years after the initial disturbance event. Stand greatest declines in size, possibly owing to the development in the severely damaged area vulnerability of this species to wind damage, lagged about 30 years behind the low and which is greater near open areas. The moderately damaged areas (Fig. 1). There were introduction of a novel functional type also marked differences in species compositon

130 between the severely damaged area versus the the Terra satellite (1/2001 – 12/2002) were less-damaged areas (Fig. 2). Red oak used, respectively. Three vegetation indices, dominated basal area in the low and moderately Normalized Difference Vegetation Index damaged areas, whereas red maple, birch (NDVI), Enhanced Vegetation Index (EVI) and species and white pine were collectively more Land Surface Water Index (LSWI), were important in the severely damaged area. The evaluated. Multi-year (1998-2001) data different areas did not converge over time; analyses have shown that EVI had a stronger black and yellow birches became more linear relationship with GPP than did NDVI. A important in the severe area over time, whereas combination of LSWI and EVI describes well a growing number of later-successional species the seasonal dynamics of leaf phenology (beech, hemlock and sugar maple) recruited (green-up (leaf flush, full leaf expansion), into the low and moderate areas. This case senescence and leaf-off). Secondly, we ran the study shows that forest recovery following satellite-based Vegetation Photosynthesis hurricane disturbance is a gradual process Model (VPM) to estimate GPP of forest at the extending beyond the timeframe of most studies flux tower site in Harvard Forest. The VPM and allows for a better understanding of the model is built upon the conceptual partitioning long-term role of hurricane disturbance in the of photosynthetically active vegetation and non- New England landscape. photosynthetic vegetation within the leaf and canopy. The input data of the VPM model are satellite-derived vegetation indices (EVI, Satellite-Based Modeling of Gross Primary LSWI), air temperature and photosynthetically Production in a Deciduous Broadleaf Forest active radiation. Seasonal dynamics of predicted GPP values from the VPM model, X. Xiao, Q. Zhang, B. Braswell, S. Urbanski, S. when using vegetation indices from the 10-day Boles, S. Wofsy, B. Moore III and D. Ojima VGT composites over 1998-2001, agreed reasonably well with observed GPP of the Net ecosystem exchange (NEE) of CO2 deciduous broadleaf forest at Harvard Forest, in between the atmosphere and forest ecosystems terms of phase and magnitude (Fig. 1). is determined by gross primary production Predicted GPP from the 8-day MODIS (GPP) of vegetation and ecosystem respiration. composites in 2001 also had a good agreement Continuous CO2 flux measurements at with observed GPP from the flux tower site individual CO2 eddy flux sites provide valuable (Fig. 2). In comparison, predicted GPP from the information on the seasonal dynamics of GPP. standard MODIS GPP/NPP product provided Satellite images also provide systematic by the MODIS Land Science Team do not observations of leaf and canopy processes. The agree well with observed GPP of forest at linkage between flux tower sites and satellite Harvard Forest in 2001. This study has remote sensing offers an opportunity to help highlighted the biophysical performance of interpret flux data and scale-up site-specific improved vegetation indices in relation to GPP flux data for the regional analysis. In this and demonstrated the potential of the VPM presentation, we report the results from model for scaling-up of GPP of deciduous analyses of a temperate deciduous broadleaf broadleaf forests. forest at Harvard Forest, Massachusetts, using satellite images and site-specific CO2 flux and climate data (1998-2001). First, we conducted analyses of improved vegetation indices in relation to the seasonal dynamics of GPP. The 10-day composites from the VEGETATION (VGT) sensor onboard the SPOT-4 satellite (4/1998 – 12/2001) and the 8-day composites from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard

131

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aaa b Robinia Stand Native stand Figure 1. Plot richness of native and nonnative species in Robinia pseudoacacia and paired native stands.

B. Von Holle, et al.

132 Figure 1. Basal area and stem density trends in the different damage areas over time. Stand development in the severely damaged area appears to lag behind the other areas.

Figure 2. Species composition changes from 1969 – 2001 in the low, moderately and severely damaged areas. Red oak dominated basal area in the low and moderately damaged areas, whereas red maple, birch species and white pine were collectively more important in the severely damaged area.

K. Wilson* et al.

133

140 140

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Figure1. The seasonal dynamics of predicted gross primary production (GPP) from the VPM model and observed GPP of forest at the flux tower site in Harvard Forest during 4/1998 – 12/2001. Vegetation indices (EVI, LSWI) derived from the 10-day VGT composite images (VGT-S10), site-specific air temperature and PAR data were used in simulation of the VPM model.

X. Xiao, et al.

134

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0 0 20406080100120140 Observed GPP (g C/m2/8-day) in 2001 from tower site

Figure 2. A comparison between the predicted and observed gross primary production (GPP) of forest in 2001 at the flux tower site in Harvard Forest, Massachusetts. Vegetation indices derived from the 8-day MODIS Surface Reflectance Product (MOD09A1), and site-specific air temperature and PAR data were used in simulation of the VPM model.

X. Xiao, et al.

135 Publications of the Harvard Forest LTER

Aber, J. 2004. Biogeochemistry: The change on biogeographical cycles in Physiology of Ecosystems. Pp. 32-40 In northeastern (U.S.) forests. Ecological D. Foster and J. Aber (Eds.), Forests in Modelling 67: 37-47. Time: The Environmental Consequences Aber, J. D. and C. T. Driscoll. 1997. Effects of of 1000 Years of Change in New England. land use, climate variation and N Yale University Press, New Haven, CT. deposition on N cycling and C storage in Aber, J. 2004. The long lens of history. Pp. northern hardwood forests. Global 394-400 In D. Foster and J. Aber (Eds.), Biogeochemical Cycles 11: 639-648. Forests in Time: The Environmental Aber, J. D. and C. A. Federer. 1992. A Consequences of 1000 Years of Change in generalized, lumped-parameter model of New England. Yale University Press, photosynthesis, evapotranspiration and net New Haven, CT. primary production in temperate and Aber, J., W. Currie, M. Castro, M. Martin, and boreal forest ecosystems. Oecologia 92: S. Ollinger. 2004. Synthesis and 463-474. extrapolation: models, remote sensing and Aber, J. D. and R. Freuder. 2000. Sensitivity of regional analysis. Pp. 338-362 In D. a forest production model to variation in Foster and J. Aber (Eds.), Forests in Time: solar radiation data sets for the Eastern The Environmental Consequences of 1000 U.S. Climate Research 15: 33-43. Years of Change in New England. Yale Aber, J. D., A. Magill, R. Boone, J. M. Melillo, University Press, New Haven, CT. P. A. Steudler, and R. Bowden. 1993. Aber, J. D. 1992. Nitrogen Cycling and Plant and soil responses to three years of Nitrogen Saturation in Temperate Forest chronic nitrogen additions at the Harvard Ecosystems. Trends in Ecology & Forest, Petersham, MA. Ecological Evolution 7: 220-223. Applications 3: 156-166. Aber, J. D. 1993. Modification of nitrogen Aber, J. D., A. Magill, S. G. McNulty, R. cycling at the regional scale: the subtle Boone, K. J. Nadelhoffer, M. Downs, and effects of atmospheric deposition. Pp. R. A. Hallett. 1995. Forest 163-174 In M. J. McDonnell and S. T. A. biogeochemistry and primary production Pickett (Eds.), Humans as Components of altered by nitrogen saturation. Water, Air Ecosystems. Springer-Verlag, NY. and Soil Pollution 85: 1665-1670. Aber, J. D. 1997. Why don't we believe the Aber, J. D., A. Magill, K. J. Nadelhoffer, J. models? Bulletin of the Ecological Society Melillo, P. Steudler, J. Hendricks, R. of America 78: 232-233. Bowden, W. Currie, W. McDowell, and Aber, J. D. 1998. Mostly a misunderstanding, I G. Berntson. 2004. Exploring the process believe. Bulletin of the Ecological Society of nitrogen saturation. Pp. 259-279 In D. of America 79: 256-257. R. Foster and J. D. Aber (Eds.), Forests in Aber, J. D. 2002. Nitrogen saturation in Time: The Environmental Consequences temperate forest ecosystems: current of 1000 Years of Change in New England. theory, remaining questions and recent Yale University Press, New Haven, CT. advances. Pp. 179-188 In Horst, W.J. et Aber, J. D. and A. H. Magill. 2004. Chronic al (Eds.), Progress in Plant Nutrition: Nigrogen Additions at the Harvard Forest: Plenary Lectures of the XIV International The First Fifteen Years of a Nitrogen Plant Nutrition Colloquium. Kluwer Saturation Experiment. Forest Ecology Academic Publishers, Dordrecht. and Management (submitted). Aber, J. D., C. Driscoll, C. A. Federer, R. Aber, J. D., W. H. McDowell, K. J. Nadelhoffer, Lathrop, G. Lovett, J. M. Melillo, P. A. H. Magill, G. Berntson, M. Kamekea, Steudler, and J. Vogelmann. 1993. A S. G. McNulty, W. Currie, L. Rustad, and strategy for the regional analysis of the I. Fernandez. 1998. Nitrogen saturation effects of physical and chemical climate in temperate forest ecosystems:

136 hypotheses revisited. BioScience 48: temporal and spatial variability. J. Atm. 921-934. Sci. 58: 2650-2667. Aber, J. D., J. M. Melillo, and C. A. Akachuku, A. E. 1991. Wood growth McClaugherty. 1990. Predicting long- determined from growth ring analysis in term patterns of mass-loss, nitrogen red pine (Pinus resinosa) trees forced to dynamics and soil organic matter lean by a hurricane. IAWA Bulletin n.s. formation from initial litter chemistry in 12: 263-274. forest ecosystems. Canadian Journal of Akachuku, A. E. 1993. Recovery and Botany 68: 2201-2208. morphology of Pinus resinosa Ait. trees Aber, J. D., J. M. Melillo, K. J. Nadelhoffer, J. 50 years after they were displaced by a Pastor, and R. Boone. 1991. Factors hurricane. Forest Ecology and controlling nitrogen cycling and nitrogen Management 56: 113-129. saturation in northern temperate forest Allen, A. 1995. Soil science and survey at ecosystems. Ecological Applications 1: Harvard Forest. Soil Survey Horizons 36: 303-315. 133-142. Aber, J. D., K. J. Nadelhoffer, P. Steudler, and J. Amthor, J. S., M. L. Goulden, J. W. Munger, M. Melillo. 1989. Nitrogen saturation in and S. C. Wofsy. 1994. Testing a northern forest ecosystems - Hypotheses mechanistic model of forest-canopy mass and implications. BioScience 39: 378- and energy exchange using eddy 386. correlation: carbon dioxide and ozone Aber, J. D., S. V. Ollinger, C. A. Federer, and C. uptake by a mixed oak-maple stand. Driscoll. 1997. Modeling nitrogen Journal of Plant Physiology 21: 623-51. saturation in forest ecosystems in response Anderson, J. A., S. Cooper-Ellis, and B. C. Tan. to land use and atmospheric deposition. 1998. New distribution notes on the Ecological Modelling 101: 61-78. mosses of Massachusetts. Rhodora 99: Aber, J. D., S. V. Ollinger, C. A. Federer, P. B. 352-367. Reich, M. L. Goulden, D. W. Kicklighter, Anderson, R. L. 2001. Integrating lateral J. M. Melillo, and Jr. R. G. L. Lathrop. expansion into models of peatland 1995. Predicting the effects of climate development in temperate new England. change on water yield and forest MFS Thesis, Harvard University. production in the northeastern U.S. Anderson, R. L., D. R. Foster, and G. Motzkin. Climate Research 5: 207-222. 2003. Integrating lateral expansion into Aber, J. D., P. B. Reich, and M. I. Goulden. models of peatland development in 1996. Extrapolating leaf CO2 exchange to temperate New England. Journal of the canopy: a generalized model of forest Ecology 91: 68-76. photosynthesis validated by eddy Bain, W. 2002. Wind-induced systematic error correlation. Oecologia 106: 257-265. in the closed dynamic chamber soil Aber, J. D., C. A. Wessman, D. L. Peterson, J. respiration measurement method. B.S. M. Melillo, and J.H. Fownes. 1989. Honors Thesis, Harvard. Remote sensing of litter and soil organic Barford, C. C. 97. Stable isotope dynamics of matter decomposition in forest denitrification. PhD Thesis, Harvard. ecosystems. Remote Sensing of Biosphere Barford, C. C., S. C. Wofsy, M. L. Goulden, J. Functioning 87-103. W. Munger, E. Hammond-Pyle, S. P. Abrams, M. D., D. A. Orwig, and J. Dockry. Urbanski, L. Hutyra, S. R. Saleska, D. 1997. Dendroecology and successional Fitzjarrald, and K. Moore. 2001. Factors status of two contrasting old-growth oak controlling long- and short-term forests in the Blue Ridge Mountains, sequestration of atmospheric CO2 in a U.S.A. Canadian Journal of Forest mid-latitude forest. Science 294: 1688- Research 27: 994-1002. 1691. Acevedo, O. C. and D. R. Fitzjarrald. 2001. Barford, C. C., S. C. Wofsy, M. L. Goulden, J. The early evening surface-layer transition: W. Munger, E. H. Pyle, S. P. Urbanski, L.

137 Hutyra, D. Fitzjarrald, and K. Moore. Long, A. Magill, J. Aber, and G. M. 2001. Factors controlling long-term rates Berntson. 2004. Effects of chronic N and inter-annual variations of CO2 additions on tissue chemistry, sequestration in a temperate forest. In: photosynthetic capacity, and carbon American Geophysical Union Conference. sequestration potential of a red pine (Pinus Barnes, D. H. 2000. Quantifying resinosa Ait.) stand in the NE United Urban/Industrial Emissions of Greenhouse States. Forest Ecology and Management and Ozone-depleting Gases Based on (Submitted). Atmospheric Observations. PhD Thesis, Bauer, G. A., G. M. Berntson, and F. A. Bazzaz. Harvard. 2001. The effect of elevated CO2 and Barnes, D. H., S. C. Wofsy, B. P. Fehlau, E. W. increased N availability on regenerating Gottlieb, J. W. Elkins, G. S. Dutton, and temperate forest communities: S. A. Montzka. 2003. Urban/industrial biochemical versus stomatal limitation of pollution for the New York City- photosynthesis. New Phytologist 152: Washington, D.C. corridor, 1996-1998: 1. 249-266. Providing independent verification of CO Bazzaz, F. A. 1990. Plant-plant interaction in and PCE emissions inventories. Journal of successional environments. Pp. 239-263 Geophysical Research 108. In J. B. Grace and G. D. Tilman (Eds.), Barnes, D. H., S. C. Wofsy, B. P. Fehlau, E. W. Perspectives on Plant Competition . Gottlieb, J. W. Elkins, G. S. Dutton, and Academic Press, San Diego, CA. S. A. Montzka. 2003. Urban/industrial Bazzaz, F. A. 1990. The response of natural pollution for the New York City- ecosystems to the rising global CO 2 Washington D. C. corridor, 1996-1998: 2. levels. Annual Review of Ecology and A study of the efficacy of the Montreal Systematics 21: 167-196. Protocol and other regulatory measures. Bazzaz, F. A. 1991. Habitat selection in plants. Journal of Geophysical Research 108. American Naturalist 137: S116-S130. Barnes, D. H., S. C. Wofsy, B. P. Fehlau, E. W. Bazzaz, F. A. 1993. Scaling in biological Gottlieb, J. W. Elkins, G. S. Dutton, and systems: Population and community P. C. Novelli. 2004. Hydrogen in the perspectives. Pp. 233-254 In .J. atmosphere: observations above a forest Ehleringer and C. B. Field (Eds.), Scaling canopy in a polluted environment. Journal Physiological Processes: Leaf to Globe. of Geophysical Research (In Press). Academic Press, Inc., San Diego, CA. Bassow, S. L. 95. Canopy photosynthesis and Bazzaz, F. A. (Ed.) 1996. Plants in Changing carbon cycling in a deciduous forest: Environments: Linking Physiological, implications of species composition and Population, and Community Ecology. rising concentrations of CO2. PhD Cambridge University Press, Cambridge, Thesis, Harvard University. England. Bassow, S. L. and F. A. Bazzaz. 1997. Intra- Bazzaz, F. A. 1997. Allocation of resources in and inter-specific variation in canopy plants: state-of-the-science and critical photosynthesis in a mixed deciduous questions. Pp. 1-37 In F. A. Bazzaz and forest . Oecologia 109: 507-515. J. Grace (Eds.), Plant Resource Bassow, S. L. and F. A. Bazzaz. 1998. How Allocation. Physiological Ecology Series environmental conditions affect leaf-level of Academic Press, San Diego, CA. photosynthesis in four deciduous tree Bazzaz, F. A. 1998. Tropical forests in a species. Ecology 79: 2660-2675. changing climate: the future of biological Bassow, S. L., K. D. M. McConnaughay, and F. diversity and impact on carbon cycle. Pp. A. Bazzaz. 1994. The response of 177-336 In S. H. Schneider (Eds.), temperate tree seedlings grown in elevated Climate Change, Special Issue: Potential CO2 to extreme temperature events. Impacts of Climate Change on Tropical Ecological Applications 4: 593-603. Forest Ecosystems. Kluwer Academic Bauer, G. A., F. A. Bazzaz, R. Minocha, S. Publishers, London.

138 Bazzaz, F. A., S. L. Bassow, G. M. Berntson, Global climate change and agricultural and S. C. Thomas. 1996. Elevated CO2 production: an assessment of current and terrestrial vegetation: implications for knowledge and critical gaps. Pp. 319-330 and beyond the global carbon budget . Pp. Global Change and Agricultural 43-76 In B. Walker and W. Steffen Production. John Wiley and Sons, Ltd., (Eds.), Global Change and Terrestrial England. Ecosystems. Cambridge University Press. Bazzaz, F. A. and K. A. Stinson. 2001. Genetic Bazzaz, F. A. and S. Catovsky. 2001. Resource versus environmental control of partitioning. Pp. 173-183 In S. Levin ecophysiological processes: some (Eds.), Encyclopedia of Biodiversity. challenges for predicting community Academic Press, San Diego. responses to global change. Pp. 283-295 Bazzaz, F. A. and S. Catovsky. 2002. Impacts In M. C. Pres, J. D. Scholes, and M. G. of global change on plants: from cells to Barker (Eds.), Physiological Plant ecosystems. Pp. 94-111 In H. A. Mooney Ecology. British Ecological Society, U. K. and J. Canadell (Eds.), Encyclopedia of Bazzaz, F. A., K. A. Stinson, and G. A. Bauer. Global Environmental Change. John 2004. Predicting terrestrial feedback on Wiley and Sons, Ltd., London. the carbon cycle: suggestions for a Bazzaz, F. A. and S. Catovsky. 2004. Initial research agenda. Global Change Biology conditions and the structure of annual (In Progress). plant communities. Journal of Ecology Bazzaz, F. A. and P. M. Wayne. 1994. Coping (In Press). with environmental heterogeneity: the Bazzaz, F. A., G. Ceballos, M. Davis, R. Dirzo, physiological ecology of tree seeding P. R. Ehrlich, T. Eisner, S. Levin, J. H. regeneration across the gap-understory Lawton, J. Lubchenco, P. A. Matson, H. continuum. Pp. 349-390 In M. Caldwell A. Mooney, P. H. Raven, J. E. and R. Pearcy (Eds.), Exploitation of Roughgarden, J. Sarukhan, G. D. Toam, P. Environmental Heterogeneity by Plants: Vitousek, B. Walker, D. H. Wall, E. O. Ecophysiological Processes Above and Wilson, and G. M. Woodwell. 1998. Below Ground . Academic Press . Editorial- Ecological science and the Bell, S. 2000. Microbial nitrogen utilization human predicament. Science 282: 879. under nitrogen-saturation conditions in Bazzaz, F. A., J. S. Coleman, and S. R. Morse. temperate forests. Senior Thesis, 1990. Growth response of seven major University of Oregon. co-occurring tree species of the Bellemare, J. 2002. Environmental and northeastern United States to elevated historical controls on the distribution and CO2. Canadian Journal of Forest Research variation of rich mesic forests in western 20: 1479-1484. Massachusetts. MFS Thesis, Harvard Bazzaz, F. A. and E. D. Fajer. 1992. Plant life University. in a CO2-rich world. Scientific American Bellemare, J., G. Motzkin, and D. Foster. 2002. 266: 68-77. Legacies of the agricultural past in the Bazzaz, F. A. and J. Grace. (Eds) 1997. Plant forested present: an assessment of Resource Allocation. Academic Press, historical land-use effects on rich mesic San Diego, CA. forests. Journal of Biogeography 29: Bazzaz, F. A. and S. L. Miao. 1993. 1401-1420. Successional status, seed size, and Berg, B. and C. McClaugherty. (2003. Plant responses of tree seedlings to CO2, light, Litter: Decomposition, Humus Formation, and nutrients. Ecology 74: 104-112. Carbon Sequestration. Springer-Verlag, Bazzaz, F. A. and W. G. Sombroek. (Eds.) 1996. Berlin. Global Climate Change and Agricultural Berlik, M. 99. The illusion of conservation. An Production. John Wiley and Sons Ltd., environmental argument for forest cutting England. in Massachusetts. Honors Thesis, Bazzaz, F. A. and W. G. Sombroek. 1996. Harvard.

139 Berlik, M. M., D. B. Kittredge, and D. R. Foster seasonal dynamics of root production and . 2002. The illusion of preservation: a loss in Betula papyrifera. Plant and Soil global environmental argument for the 190: 211-216. local production of natural resources. Berntson, G. M. and F. A. Bazzaz. 1997. Harvard Forest Paper #26 . Nitrogen cycling in microcosms of yellow Berlik, M. M., D. B. Kittredge, and D. R. Foster birch exposed to elevated CO2: . 2002. The illusion of preservation: a simultaneous positive and negative global environmental argument for the belowground feedbacks. Global Change local production of natural resources. Biology 3: 247-258. Journal of Biogeography 29: 1557-1568. Berntson, G. M. and F. A. Bazzaz. 1998. Berliner, R. and J. G. Torrey. 1989. On Regenerating temperate forest microcosms tripartite Frankia - mycorrhizal in elevated CO2: species composition, associations in the Myricaceae. Canadian belowground growth and nitrogen cycling. Journal of Botany 67: 1708-1712. Oecologia 113: 115-125. Berliner, R. and J. G. Torrey. 1989. Studies on Berntson, G. M., J. P. Lynch, and S. Snapp. mycorrhizal associations in Harvard 1998. Fractal geometry and the Forest, Massachusetts. Canadian Journal description of plant root systems: current of Botany 67: 2245-2251. perspectives and future applications. Pp. Bernardos, D., D. R. Foster, G. Motzkin, and J. 113-152 In Baveye, Parlage, and Smith Cardoza. 2004. Wildlife dynamics in the (Eds.), Chaos and Fractals in Soil changing New England landscape. Pp. Science. CRC Press, Boca Raton. 142-168 In D. Foster and J. Aber (Eds.), Berntson, G. M., N. Rajakaruna, and F. A. Forests in Time: The Environmental Bazzaz . 1998. Species- and community- Consequences of 1000 Years of Change in level growth and nitrogen acquisition in New England. Yale University Press, elevated CO2 atmospheres in an New Haven, CT. experimental annual community. Global Berntson, G. 96. Root growth and nitrogen Change Biology 4: 101-120. cycling in temperate deciduous forests in Berntson, G. M. and P. Stoll. 1997. Correcting an elevated CO2 world. PhD Thesis, for finite spatial scales of self-similarity Harvard. when calculating the fractal dimensions of Berntson, G. M. 1997. Topological scaling and real-world structures. Proceedings of plant root system architecture: Royal Society, Biological Sciences 264: developmental and functional hierarchies. 1531-1537. New Phytologist 135: 621-634. Berntson, G. M., P. M. Wayne, and F. A. Berntson, G. M. and J. D. Aber. 2000. Fast Bazzaz. 1997. Belowground architectural nitrate immobilization in N-saturated and mycorrhizal responses to elevated temperate forest soils. Soil Biology and CO2 in Betula alleghaniensis populations. Biochemistry 32: 151-156. Functional Ecology 11: 684-695. Berntson, G. M. and F. A. Bazzaz. 1996. The Bishop, G. D., M. R. Church, J. D. Aber, R. P. allometry of root production and loss in Neilson, S. V. Ollinger, and C. Daley. seedlings of Acer rubrum (Aceraceae) and 1998. A comparison of mapped estimates Betula papyrifera (Betulaceae): of long-term runoff in the northeastern implications for root dynamics in elevated United States. Journal of Hydrology 206: CO2. American Journal of Botany 83: 176-190. 608-616. Blackman, R. 2000. The determination of the Berntson, G. M. and F. A. Bazzaz. 1996. relationship between wood respiration and Belowground positive and negative sapwood temperature in an old growth feedbacks on CO2 growth enhancement. eastern hemlock (Tsuga canadensis) Plant and Soil 187: 119-131. stand. Senior Thesis, University of Berntson, G. M. and F. A. Bazzaz. 1997. Edinburgh. Elevated CO2 and the magnitude and Bliss, J., G. Aplet, C. Hartzell, P. Harwood, P.

140 Jahnige, D. Kittredge, S. Lewandowski, historical variation in hurricanes across and M. L. Soscia. 2001. Community- the Yucatan Peninsula. Pp. 495-516 In A. based Ecosystem Monitoring. Journal of Gómez-Pompa, M. F. Allen, S. L. Fedick, Sustainable Forestry 12: 143-167. and J. J. Jiménez (Eds.), Lowland Maya Bolster, K. L., M. E. Martin, and J. D. Aber. Area: Three Millennia at the Human- 1996. Interactions between precision and Wildland Interface. Haworth Press, New generality in the development of York. calibrations for the determination of Boose, E. R., D. R. Foster, and M. Fluet. 1994. carbon fraction and nitrogen concentration Hurricane impacts to tropical and in foliage by near infrared reflectance. temperate forest landscapes. Ecological Canadian Journal of Forest Research 26: Monographs 64: 369-400. 590-600. Boose, E. R., M. I. Serrano, and D. R. Foster. Bond, R. S. 1998. Professional Forestry, 2004. Landscape and regional impacts of forestry education and research. Pp. 220- hurricanes in Puerto Rico. Ecological 225 In C. H. W. Foster (Eds.), Stepping Monographs (In Press). Back to Look Forward - a History of the Bowden, R., M. C. Castro, J. M. Melillo, P. A. Massachusetts Forest. Harvard Forest, Steudler, and J. D. Aber. 1993. Fluxes of Petersham, MA. greenhouse gases between soils and the Boone, R. D., K. J. Nadelhoffer, J. D. Canary, atmosphere in a temperate forest and J. P. Kaye. 1998. Roots determine following a simulated hurricane the temperature sensitivity of soil blowdown. Biogeochemistry 21: 61-71. respiration. Nature 396: 571-572. Bowden, R. D., E. Davidson, K. Savage, C. Boose, E. R. 2003. Hurricane impacts in New Arabia, and P. Steudler. 2004. Chronic England and Puerto Rico. Pp. 25-42 In nitrogen additions reduce total soil D. Greenland, G. Goodin, and R. C. Smith respiration and microbial respiration in (Eds.), Climate Variability and Ecosystem temperate forest soils at the Harvard Response at Long-term Ecological Forest. Forest Ecology and Management Research Sites. Oxford University Press, (submitted). U.K. Bowden, R. D., E. Davidson, K. Savage, C. Boose, E. R. 2004. A historical-modeling Arabia*, and P. Steudler. 2004. Long- method for reconstructing hurricane term suppression of soil respiration by impacts . In R. Murnane and K. Liu nitrogen deposition: contribution of (Eds.), Hurricanes and typhoons: Past, microbial decomposition. Forest Ecology Present and Future. Columbia University and Management (Submitted). Press, (In Press). Bowden, R. D., J. M. Melillo, P. A. Steudler, Boose, E. R., E. F. Boose, and A. L. Lezberg. and J. D. Aber. 1991. Effects of nitrogen 1998. A practical method for mapping additions on annual nitrous oxide fluxes trees using distance measurements. from temperate forest soils in the Ecology 79: 819-827. northeastern United States. Journal of Boose, E. R., K. E. Chamberlin, and D. R. Geophysical Research 96: 9321-9328. Foster . 1997. Reconstructing historical Bowden, R. D., K. J. Nadelhoffer, R. D. Boone, hurricanes in New England. In: 22nd J. M. Melillo, and J. B. Garrison. 1993. Conference on Hurricanes and Tropical Contributions of aboveground litter, Meteorology. American Meteorological belowground litter, and root respiration to Society, Boston, MA. total soil respiration in a temperate mixed Boose, E. R., K. E. Chamberlin, and D. R. hardwood forest. Canadian Journal of Foster . 2001. Landscape and regional Forest Research 123: 1402-1407. impacts of hurricanes in New England. Bowden, R. D., K. M. Newkirk, and G. M. Ecological Monographs 7: 27-48. Rullo. 1998. Carbon dioxide and Boose, E. R., D. R. Foster, A. Barker Plotkin, methane fluxes by a forest soil under and B. Hall. 2003. Geographical and laboratory-controlled moisture and

141 temperature conditions. Soil Biology Catosvky, S. and F. A. Bazzaz. 1999. Elevated Biochemistry 30: 1591-1597. CO2 influences the responses of two birch Bowden, R. D., P. A. Steudler, J. M. Melillo, species to soil moisture: implications for and J. D. Aber. 1990. Annual nitrous forest community structure. Global oxide fluxes from temperate forest soils in Change Biology 5: 507-518. the northeastern United States. Journal of Catovsky, S. 1998. Functional groups: Geophysical Research 95: 13997-14005. clarifying our use of the term. Bulletin of Bryant, A*. 2000. Sustainable forest the Ecological Society of America 79: management and forest certification on the 126-127. Southern Yucatan Peninsula, Mexico. Catovsky, S. 1998. Taking a Functional View Undergraduate Thesis, Oregon State of Ecosystems (book review). Ecology University. 79 : 1843-1844. Buckley, H. L., T. E. Miller, A. M. Ellison, and Catovsky, S. 2000. Linking community N. J. Gotelli. 2003. Reverse latitudinal dynamics and ecosystem function in trends in species richness of pitcher-plant mixed conifer broad-leaved forests. Ph.D food webs. Ecology Letters 6: 825-829. Thesis, Harvard. Bürgi, M. 1998. Wie veränderte sich der Wald Catovsky, S. and F. A. Bazzaz. 2000. als Lebensraum im 19. und 20. Contributions of coniferous and broad- Jahrundert? - ein Fallbeispiel aus dem leaved species to mixed forest carbon Zürcher Unterund Weinland. Schweiz Z. uptake: A bottom-up approach. Canadian Forstwes. 149: 758-769. Journal of Forest Research 30: 100-111. Bürgi, M., E. W. B. Russell, and G. Motzkin. Catovsky, S. and F. A. Bazzaz. 2000. The role 2000. Effects of postsettlement human of resource interactions and seedling activities on forest composition in the regeneration in maintaining a positive north-eastern United States: a comparative feedback in hemlock stands. Journal of approach. Journal of Biogeography 27: Ecology 88: 100-112. 1123-1128. Catovsky, S. and F. A. Bazzaz. 2002. Carlton, C. G. and F. A. Bazzaz. 1998. Feedbacks between canopy composition Regeneration of three sympatric birch and seedling regeneration in mixed conifer species on experimental hurricane broad-leaved forests. Oikos 98: 403-420. blowdown microsites. Ecological Catovsky, S. and F. A. Bazzaz. 2002. Nitrogen Monographs 68: 99-120. availability influences regeneration of Carlton, G. 93. Effects of microsite coniferous and broad-leaved tree species environment on tree regeneration in the understory seedling bank. following disturbance. PhD Thesis, Ecological Applications 12: 1056-1070. Harvard. Catovsky, S. and F. A. Bazzaz. 2002. Plant Carlton, G. C. and F. A. Bazzaz. 1998. competition in an elevated CO2 world. Pp. Resource availability, heterogeneity, and 471-481 In H. A. Mooney and J. Canadell congruence following simulated hurricane (Eds.), Encyclopedia of Global Change. blowdown of a temperate forest. Ecology John Wiley and Sons, Ltd., Chichester, 79: 1305-1319. England. Castro, M. S., J. M. Melillo, P. A. Steudler, and Catovsky, S. and F. A. Bazzaz. 2004. Forest J. W. Chapman. 1995. Soil moisture as a regeneration dynamics: current patterns predictor of methane uptake by temperate and future responses to global forest soils. Canadian Journal of Forest environmental change. In D. R. Foster Research 24: 1805-1810. and J. D. Aber (Eds.), Forests in Time: Castro, M. S., P. A. Steudler, J. M. Melillo, J. D. The Environmental Consequences of 1000 Aber, and R. D. Bowden. 1995. Factors Years of Change in New England. controlling atmospheric methane Catovsky, S., R. Crabtree, T. Sipe, G. Carlton, S. consumption by temperate forest soils. Bassow, L. George, and F. A. Bazzaz. Global Biogeochemical Cycles 9: 1-10. 2004. Experimental approaches to

142 understanding forest regeneration. Pp. Yucatán: Final Frontiers. Oxford 316-337 In D. Foster and J. Aber (Eds.), University Press, New York. Forests in Time: The Environmental Ciccarello, S. C. 97. A study of the effects of Consequences of 1000 Years of Change in microclimate on leaf phenology of scrub New England. Yale University Press, oak (Quercus ilicifolia) on Montague New Haven, CT. Plain. MS Thesis, Antioch New England Catovsky, S., N. M. Holbrook, and F. A. Graduate School. Bazzaz. 2002. Coupling whole-tree Cobb, R. C. and D. A. Orwig. 2002. Impact of transpiration and canopy photosynthesis in hemlock woolly adelgid on coniferous and broad-leaved tree species. decomposition: an overview. In: Canadian Journal of Forest Research 32: Symposium on the Hemlock Woolly 295-309. Adelgid in Eastern North America Cavender-Bares, J., S. Apostol, I. Moya, J. M. Proceedings. New Jersey Agricultural Briantais, and F. A. Bazzaz. 1999. Experiment Station, New Jersey. Chilling-induced photoinhibition in oaks: Cogbill, C., J. Burk, and G. Motzkin. 2002. are evergreen leaves inherently better The forests of presettlement New England, protected than deciduous leaves? USA: Spatial and compositional patterns Photosynthetica 587-596. based on town proprietor surveys. Journal Cavender Bares, J. and F. A. Bazzaz. 2000. of Biogeography 29: 1279-1304. Changes in drought response strategies Compton, J. and R. Boone. 2004. Land-use with ontogeny in Quercus rubra: legacies on soil properties and nutrients. implications for scaling from seedlings to Pp. 189-201 In D. Foster and J. Aber mature trees. Oecologia 124: 8-18. (Eds.), Forests in Time: The Cavender-Bares, J., F. A. Bazzaz, and K. A. Environmental Consequences of 1000 Stinson. 2004. Terrestrial photosynthesis: Years of Change in New England. Yale the ecological viewpoint. In Papageorgiou University Press, New Haven, CT. and Govindgee (Eds.), Chlorophyll Compton, J., L. Watrud, A. Porteus, and S. Fluorescence: A Signature of Bell*. 2004. Microbial biomass and Photosynthesis. Kluwer Academic Press, diversity after long-term nitrogen Germany (In Press). additions at Harvard Forest. Forest Cavender-Bares, J. and N. M. Holbrook. 2001. Ecology and Management (Submitted). Hydraulic properties and freezing-induced Compton, J. E. and R. Boone. 2000. Long-term cavitation in sympatric evergreen and impacts of agriculture on soil carbon and deciduous oaks with contrasting habitats. nitrogen in New England forests. Plant, Cell and Environment 24: 1243- Ecology 81: 2314-2330. 1256. Compton, J. E., R. D. Boone, G. Motzkin, and Cavender-Bares, J., M. Potts, E. Zacharias, and D. R. Foster. 1998. Soil carbon and F. A. Bazzaz. 2000. Consequences of nitrogen in a pine-oak sand plain in central CO2 and light interactions for leaf Massachusetts: role of vegetation and phenology, growth, and senescence in land-use history. Oecologia 116: 536- Quercus rubra. Global Change Biology 542. 6: 877-887. Compton, J. E., L. S. Watrud, L. A. Porteous, Chowdhury, R. R., L. Schneider, with Y. and S. DeGrood. 2004. Response of Soil Ogneva-Himmelberger Pedro Marcario Microbial Biomass and Community Mendoza, S. C. Villar, and A. Barker- Composition to Chronic Nitrogen Plotkin. 2004. Land Cover and Land Additions at Harvard Forest. Forest Use: Classification and Ecology and Management (submitted). Change Analysis. In B. L. Turner, J. Cooper-Ellis, S. 1998. Bryophytes in old- Geoghegan, and D. R. Foster (Eds.), growth forests of western Massachusetts . Integrated Land Change Science and Journal of the Torrey Botanical Society Tropical Deforestation in Southern 125: 117-132.

143 Cooper-Ellis, S., D. R. Foster, G. Carlton, and debris at the Harvard Forest. Ecosystems A. Lezberg. 1999. Forest response to 5: 446-460. catastrophic wind: results from an Currie, W. S., K. J. Nadelhoffer, and J. D. Aber . experimental hurricane . Ecology 80: 1999. Soil detrital processes controlling 2683-2696. the movement of 15N tracers to forest Crabtree, R. C. 92. Birch regeneration in a vegetation. Ecological Applications 9: changing nitrogen environment. Ph.D. 87-102. Thesis, Harvard. Currie, W. S., K. J. Nadelhoffer, and J. D. Aber . Crabtree, R. C. and F. A. Bazzaz. 1993. Black 2004. Decadal scale turnover of soil birch (Betula lenta L.) seedlings as organic N at the Harvard Forest: an foragers for nitrogen. New Phytologist inverse modeling analysis of ecosystem- 122: 617-625. level 15N tracer redistributions. Forest Crabtree, R. C. and F. A. Bazzaz. 1993. Ecology and Management (Submitted). Seedling response of four birch species to Currie, W. S., K. J. Nadelhoffer, and J. D. Aber . simulated nitrogen deposition: 2004. Decadal time series in 15N Ammonium versus nitrate. Ecological indicate forest C response is controlled by Applications 3: 315-321. fast turnover and replenishment of light- Currie, W. 1999. The responsive C and N fraction mineral soil organic N. Forest biogeochemistry of the temperate forest Ecology and Management (submitted). floor. TREE 14: 316-320. Currie, W. S., K. J. Nadelhoffer, and B. Colman. Currie, W. S. 95. Forest floor leachate 2002. Long-term movement of 15N biogeochemistry and decomposition tracers into fine woody debris under dynamics. PhD Thesis, University of New chronically elevated N inputs. Plant and Hampshire. Soil 238: 313-323. Currie, W. S. 2003. Relationships between Curry, B. 2002. The initial impact of a selective carbon turnover and bioavailable energy harvest on aboveground carbon storage in fluxes in two temperate forest soils. a northern temperate forest. B.S. Honors Global Change Biology 9: 919-929. Thesis, Notre Dame. Currie, W. S. and J. D. Aber. 1997. Modeling Curtis, P. S., P. J. Hanson, P. Bolstad, C. leaching as a decomposition process in Barford, J. C. Randolph, H. P. Schmid, humid, montane forests. Ecology 78: and K. B. Wilson. 2002. Biometric and 1844-1860. eddy-covariance based estimates of annual Currie, W. S., J. D. Aber, and C. T. Driscoll. carbon storage in five eastern North 1999. Leaching of nutrient cations from American deciduous forests. Agiculture the forests floor: effects of nitrogen and Forest Meteorology 113: 3-19. saturation in two long-term manipulations. Czikowsky, M. J. and D. R. Fitzjarrald. 2001. Canadian Journal of Forest Research 29: Seasonal and successional effects on 609-620. streamflow in the northeast. Eos. Trans. Currie, W. S., J. D. Aber, W. H. McDowell, R. AGU 82 (80). D. Boone, and A. H. McGill. 1996. Dail, D. B., E. A. Davidson, and J. Chrover. Vertical transport of dissolved organic C 2001. Rapid abiotic transformation of and N under long-term N amendments in nitrate in an acid forest soil. pine and hardwood forests. Biochemistry Biogeochemistry 54: 131-146. 35: 471-505. Davidson, E. A., E. Belk, and R. D. Boone. Currie, W. S. and K. J. Nadelhoffer. 1999. 1998. Soil and water content and Dynamic redistribution of isotopically temperature as independent or confounded labeled cohorts of nitrogen inputs in two factors controlling soil respiration in a temperate forests. Ecosystems 2: 4-18. temperate mixed hardwood forest. Global Currie, W. S. and K. J. Nadelhoffer. 2003. The Change Biology 4: 217-228. imprint of land use history: patterns of Davidson, E. A., K. Savage, L. V. Verchot, and carbon and nitrogen in downed woody R. I. *. Navarro. 2003. Minimizing

144 artifacts and biases in chamber-based Eberhardt, R. 2001. Implications of land-use measurements of soil respiration. legacies in the sand plain vegetation of Agricultural and Forest Meteorology 113: Cape Cod National Seashore. MFS 21-37. Thesis, Harvard. Donohue, K. 2002. Germination timing Eberhardt, R., D. R. Foster, G. Motzkin, and B. influences natural selection on life-history Hall. 2003. Conservation of changing characters in Arabidopsis thaliana. landscapes: vegetation, land-use history, Ecology 83: 1006-1016. and fire on Cape Cod National Seashore. Donohue, K. 2003. The influence of neighbor Ecological Applications 13: 68-84. relatedness on multilevel selection in the Ellison, A. M. 2003. Wetlands of Central Great lakes sea rocket. The American America. Wetlands Ecology & Naturalist 162: 77-92. Management 12: 3-55. Donohue, K. 2003. Setting the stage: Ellison, A. M., E. J. Farnsworth, and N. J. phenotypic plasticity as habitat selection. Gotelli. 2002. Ant diversity in pitcher- International Journal of Plant Sciences plant bogs of Massachusetts. Northeastern (special issue) 164: S79-S92. Naturalist 9: 267-284. Donohue, K. 2004. Density-dependent Ellison, A. M., N. J. Gotelli, J. S. Brewer, L. multilevel selection in the Great Lakes sea Cochran-Stafira, J. Kneitel, T. E. Miller, rocket. Ecology 85: 180-191. A. S. Worley, and R. Zamora. 2003. The Donohue, K., D. R. Foster, and G. Motzkin. evolutionary ecology of carnivorous 2000. Effects of the past and the present plants. Advances in Ecological Research on species distributions: land-use history 33: 1-74. and demography of wintergreen. Journal Esquivel, R. 2000. Presence of Hypsipyla of Ecology 88: 303-316. grandella in plantations of Cedrela Donohue, K., A. C. Warneka, and J. Dickey. odorata and Swietenia macrophylla in 2004. Identifying mechanisms of Calakmul, Campeche, Mexico. Journal of seasonal cueing of germination using Tropical Ecology (notes). Arabidopsis mutants. Heredity (In Fan, S.-M., M. L. Goulden, J. W. Munger, B. C. Review). Daube, P. S. Bakwin, S. C. Wofsy, J. S. Downs, M. R., R. H. Michener, B. Fry, and K. J. Amthor, D. R. Fitzjarrald, K. E. Moore, Nadelhoffer. 1999. Routine measurement and T. R. Moore. 1995. Environmental of dissolved inorganic 15N in streamwater. controls on the photosynthesis and Environmental Monitoring & Assessment respiration of a boreal lichen woodland: a 55: 211-220. growing season of whole-ecosystem Downs, M. R., K. J. Nadelhoffer, J. M. Melillo, exchange measurements by eddy and J. D. Aber. 1993. Foliar and fine root correlation. Oecologia 102: 443-452. nitrate reductase activity in seedlings of Feigl, B. J., J. M. Melillo, and C. C. Cerri. 1995. four forest tree species in relation to Changes in the origin and quality of soil nitrogen availability. Trees, Structure and organic matter after pasture introduction Function 7: 233-236. in Rondônia (Brazil). Plant and Soil 175: Downs, M. R., K. J. Nadelhoffer, J. M. Melillo, 21-29. and J. D. Aber. 1996. Immobilization of Feild, T. S., D. W. Lee, and N. M. Holbrook. a 15N labelled nitrate addition by 2001. Why leaves turn red in autumn: the decomposing forest litter. Oecologia 105: role of anthocyanims in senescing leaves 141-150. of red-osier dogwood (Cornus Dunwiddie, P., D. Foster, D. Leopold, and R. stolonifera). Plant Physiology 127: 566- Leverett. 1996. Old-growth forests of 574. southern New England, New York and Fenn, M. E., M. Poth, J. D. Aber, J. S. Baron, B. Pennsylvania. Pp. 126-143 In M. B. T. Bormann, D. W. Johnson, A. D. Lemly, Davis (Eds.), Eastern Old Growth Forests. S. G. McNulty, D. F. Ryan, and R. Island Press, Covelo, CA. Stottlemeyer. 1998. Nitrogen excess in

145 North American ecosystems: a review of University Press, New Haven, CT. predisposing factors, geographic extent, Foster, D., J. Aber, R. Bowden, J. Melillo, and ecosystem responses and management F. Bazzaz. 2004. Comparison between strategies. Ecological Applications 8: physical disturbance and novel stresses. 706-733. Pp. 296-299 In D. Foster and J. Aber Finley, A. O. 2002. Forest owner attitudes (Eds.), Forests in Time: The towards management at a multi-property Environmental Consequences of 1000 scale. MS Thesis, University of Years of Change in New England. Yale Massachusetts. University Press, New Haven, CT. Finnie, T. C., C. D. Tomlin, J. Bossler, D. Foster, D., S. Clayden, D. A. Orwig, B. Hall, Cowen, B. Petchenik, H. Thomas, T. and S. Barry. 2002. Oak, chestnut and Wilbanks, and J. Estes. (1990. Spatial fire: climatic and cultural controls of data needs: the future of the national long-term forest dynamics in New mapping program. National Academy England. Journal of Biogeography 29: Press, Washington, D. C. 1359-1379. Fitzjarrald, D. R., O. C. Acevedo, and K. E. Foster, D., S. Cooper-Ellis, A. Barker Plotkin, Moore. 2001. Climatic consequences of G. Carlton, R. Bowden, A. Magill, and J. leaf presence in the eastern United States. Aber. 2004. Simulating a catastropic J. Climate 14: 598-614. hurricane. Pp. 235-258 In D. Foster and Foster, C. H. W. (Ed.) 1998. Stepping Back to J. Aber (Eds.), Forests in Time: The Look Forward - a History of the Environmental Consequences of 1000 Massachusetts Forest. Harvard Forest and Years of Change in New England. Yale Harvard University Press, Petersham and University Press, New Haven, CT. Cambridge. Foster, D., B. Hall, S. Barry, S. Clayden, and T. Foster, C. H. W. and D.R. Foster. 1999. Parshall. 2002. Cultural, environmental, Thinking in Forest Time - A Strategy for and historical controls of vegetation the Massachusetts Forest. Harvard Forest patterns and the modern conservation Paper No. 24. setting on the island of Martha's Vineyard, Foster, D. and J. Aber. 2004. Background and U.S.A. Journal of Biogeography 29: framework for long -term ecological 1381-1400. research. Pp. 3-18 In D. Foster and J. Foster, D., D. Knight, and J. Franklin. 1998. Aber (Eds.), Forests in Time: The Landscape patterns and legacies of large Environmental Consequences of 1000 infrequent disturbances. Ecosystems 1: Years of Change in New England. Yale 497-510. University Press, New Haven, CT. Foster, D., G. Motzkin, D. Bernardos, and J. Foster, D. and J. Aber. (Eds) 2004. Forests in Cardoza. 2002. Wildlife dynamics in the Time: The Environmental Consequences changing New England landscape. Journal of 1000 Years of Change in New England . of Biogeography 29: 1337-1357. Yale University Press, New Haven, CT. Foster, D., G. Motzkin, J. O'Keefe, E. Boose, D. Foster, D. and J. Aber. 2004. Overviews of the Orwig, J. Fuller, and B. Hall. 2004. The experiments and approaches. In D. Foster environmental and human history of New and J. Aber (Eds.), Forests in Time: The England. Pp. 43-100 In D. Foster and J. Environmental Consequences of 1000 Aber (Eds.), Forests in Time: The Years of Change in New England. Yale Environmental Consequences of 1000 University Press, New Haven, CT. Years of Change in New England. Yale Foster, D. and J. Aber. 2004. The Physical and University Press, New Haven, CT. Biological Setting for Ecological Foster, D., G. Motzkin, and B. Slater. 1998. Research. Pp. 19-31 In D. Foster and J. Land-use history as long-term broad-scale Aber (Eds.), Forests in Time: The disturbance: regional forest dynamics in Environmental Consequences of 1000 central New England. Ecosystems 1: 96- Years of Change in New England. Yale 119.

146 Foster, D. R. 1988. Disturbance history, future trends: an example from the US community organization and vegetation Long Term Ecological Research (LTER) dynamics of the old-growth Pisgah Forest, Program. PAGES Newsletter 8: 23-25. southwestern New Hampshire, U.S.A. Foster, D. R. 2001. Conservation lessons and Journal of Ecology 76: 105-134. challenges from ecological history. Forest Foster, D. R. 1988. Species and stand response History Today Fall 2000: 2-11. to catastrophic wind in central New Foster, D. R. 2001. New England's Forest England, U.S.A. Journal of Ecology 76: Primeval. Wild Earth 11: 40-44. 135-151. Foster, D. R. 2002. Conservation issues and Foster, D. R. 1992. Land-use history (1730- approaches for dynamic cultural 1990) and vegetation dynamics in central landscapes. Journal of Biogeography 29: New England, USA. Journal of Ecology 1533-1535. 80: 753-772. Foster, D. R. 2002. Insights from historical Foster, D. R. 1993. Land-use history and forest geography to ecology and conservation: transformations in central New England. lessons from the New England landscape. Pp. 91-110 In S. Pickett and M. Journal of Biogeography 29: 1269-1275. McDonald (Eds.), Humans as Components Foster, D. R. 2002. Thoreau's country: a of Ecosystems. Springer-Verlag, NY. historical-ecological approach to Foster, D. R. 1995. Land-use history and four conservation of the New England hundred years of vegetation change in landscape. Journal of Biogeography 29: New England. Pp. 253-319 In B. L. 1537-1555. Turner , A. G. Sal, F. G. Bernaldez, and F. Foster, D. R., J. Aber, J. Melillo, R. D. Bowden, DiCastri (Eds.), .Global Land Use and F. A. Bazzaz. 1998. Forest response Change: a Perspective from the to natural disturbance versus human- Columbian Encounter. SCOPE induced stresses. Arnoldia 58: 35-40. Publication, Consejo Superior de Foster, D. R., J. D. Aber, J. M. Melillo, R. Investigaciones Cientificas, Madrid. Bowden, and F. Bazzaz. 1997. Forest Foster, D. R. 1999. Forests the way they used to response to disturbance and anthropogenic be. C-4. New York. stress. Rethinking the 1938 Hurricane and Foster, D. R. (1999. Thoreau's Country: the impact of physical disturbance vs Journey Through a Transformed chemical and climate stress on forest Landscape. Harvard University Press, ecosystems. BioScience 47: 437-445. Cambridge, MA. Foster, D. R. and E. Boose. 1992. Patterns of Foster, D. R. 2000. From bobolinks to bears: forest damage resulting from catastrophic interjecting geographical history into wind in central New England, USA. ecological studies, environmental Journal of Ecology 80: 79-99. interpretation, and conservation planning. Foster, D. R. and E. Boose. 1992. Technology Journal of Biogeography 27: 27-30. development in the LTER Network - Foster, D. R. 2000. Hemlock's future in the Current status of GIS, remote sensing, context of its history: an ecological Internet connectivity, archival storage and perspective. In: Sustainable Management global positioning systems. LTER of Hemlock Ecosystems in Eastern North Publication, Seattle, WA. America. USDA GRT-NE, Symposium Foster, D. R. and E. Boose. 1995. Hurricane Proceedings. disturbance regimes in temperate and Foster, D. R. 2000. Linking the deep and recent tropical forest ecosystems. Pp. 305-339 past to the modern New England In M. Coutts and J. Grace (Eds.), Wind Landscape. Rhodora 102: 278-279. and Trees. Cambridge University Press, Foster, D. R. 2000. The primeval forests of Cambridge. New England. Sanctuary. 39: 9-12. Foster, D. R., M. Fluet, and E. R. Boose. 1999. Foster, D. R. 2000. Using history to interpret Human or natural disturbance: landscape- current environmental conditions and scale dynamics of the tropical forests of

147 Puerto Rico. Ecological Applications 9: paleoecology to community ecology. 555-572. Trends in Ecology and Evolution 5: 119- Foster, D. R. and G. Motzkin. 1998. Ecology 122. and conservation in the cultural landscape Foster, D. R. and B. L. Turner. 2004. The Long of New England: lessons from nature's View: Human--Environment history. Northeastern Naturalist 5: 111- Relationships, 1000 BC--AD 1900. Pp. 126. 23-37 In B. L. Turner, J. Geoghegan, and Foster, D. R. and G. Motzkin. 1999. Historical D. R. Foster (Eds.), Integrated Land influences on the landscape of Martha's Change Science and Tropical Vineyard: perspectives on the Deforestation in Southern Yucatán: Final management of the Manuel F. Correllus Frontiers. Oxford University Press, New State Forest. Harvard Forest Paper No. 23. York. Foster, D. R. and G. Motzkin. 2003. Foster, D. R., T. Zebryk, P. Schoonmaker, and Interpreting and conserving the openland A. Lezberg. 1992. Post-settlement habitats of coastal New England: insights history of human land-use and vegetation from landscape history. Forest Ecology dynamics of a hemlock woodlot in central and Management 185: 127-150. New England. Journal of Ecology 80: Foster, D. R., G. Motzkin, D. Orwig, J. Aber, J. 773-786. Melillo, R. Bowden, and F. Bazzaz. 1998. Foster, D. R. and T. M. Zebryk. 1993. Long- Case studies in forest history and ecology term vegetation dynamics and disturbance from the Harvard Forest. Arnoldia 58: history of a Tsuga -dominated forest in 32-44. New England. Ecology 74: 982-998. Foster, D. R. and J. O'Keefe. (Eds.) 2000. New Francis, D. R. and D. R. Foster. 2001. England Forests Through Time: Insights Response of small New England ponds to from the Harvard Forest Dioramas. historic land use. The Holocene 11: 301- Harvard Forest and Harvard University 312. Press, Petersham and Cambridge . Freedman, J. M. and D. R. Fitzjarrald. 2001. Foster, D. R., D. A. Orwig, and J. S. McLachlan. Postfrontal airmass modification. J. 1996. Ecological and conservation Hydromet 419-437. insights from reconstructive studies of Freedman, J. M., D. R. Fitzjarrald, K. E. Moore, temperate old-growth forests. Trends in and R. K. Sakai. 2001. Boundary layer Ecology and Evolution 11: 419-424. clouds and vegetation-atmosphere Foster, D. R., Orwig, D. A., and O'Keefe, J. feedbacks. J. Climate 14: 180-197. 1996. Evaluation of the old-growth forest Frey, S. D. and M. Knorr. 2004. Chronic at Mount Wachusett, central nitrogen enrichment affects the structure Massachusetts. Commonwealth of and function of the soil microbial Massachusetts , 9 pp. Department of community . Forest Ecology and Environmental Management. Management (Submitted). Foster, D. R., Orwig, D. A., and O'Keefe, J. F. Frey, S. D. K. M., J. L. Parrent, and R. T. 1997. Impact of development on the Simpson. 2004. Chronic Nitrogen forests of Wachusett Mountain. Enrichment Affects the Structure and Commonwealth of Massachusetts , 15 pp. Function of the Soil Microbial Department of Environmental Community in Temperate Hardwood and Management. Pine Forests. Forest Ecology and Foster, D. R., Orwig, D. A., and O'Keefe, J. F. Management (in press). 1997. Old-growth forest monitoring on Fry, B., D. E. Jones, G. W. Kling, R. B. Wachusett Mountain. Commonwealth of McKane, K. J. Nadelhoffer, and B. J. Massachusetts , 12 pp. Department of Peterson. 1995. Adding 15N tracers to Environmental Management. ecosystem experiments. In E. Wada, T. Foster, D. R., P. K. Schoonmaker, and S. T. A. Yoneyama, M. Minagawa, T. Ando, and Pickett. 1990. Insights from B. Fry (Eds.), Stable Isotopes in the

148 Biosphere. Kyoto University Press, understory as an ecological filter: growth Kyoto, Japan. and survival of canopy tree seedlings. Fuller, J., D. R. Foster, G. Motzkin, J. Ecology 80: 846-856. McLachlan, and S. Barry. 2004. Broad- Gerhardt, F. 93. Physiographic and historical scale forest response to land-use and influences of forest composition in central climate change. Pp. 101-124 In D. New England, U.S.A. MFS Thesis, Foster and J. Aber (Eds.), Forests in Time: Harvard. The Environmental Consequences of 1000 Gerhardt, F. and D. R. Foster. 2002. Years of Change in New England. Yale Physiographic and historical effects on University Press, New Haven, CT. forest vegetation in central New England, Fuller, J. L. 1997. Holocene forest dynamics in USA. Journal of Biogeography 29: 1421- southern Ontario, Canada: fine-resolution 1437. pollen data. Canadian Journal of Botany Godbold, D. L. and G. M. Berntson. 1997. 75: 1714-1727. Elevated atmospheric CO2 concentrations Fuller, J. L. 1998. Ecological impact of the lead to changes in ectomycorrhizal mid-Holocene hemlock decline in morphotype assemblages in Betula southern Ontario, Canada. Ecology 79: papyrifera. Tree Physiology 17: 347-350. 2337-2351. Godbold, D. L., G. M. Berntson, and F. A. Fuller, J. L., D. R. Foster, J. S. McLachlan, and Bazzaz . 1997. Growth and mycorrhizal N. Drake. 1998. Impact of human colonization of three North-American tree activity on regional forest composition species under elevated atmospheric CO2. and dynamics in central New England. New Phytologist 137: 433-440. Ecosystems 1: 76-95. Goldstein, A. H. 94. Non-methane Gaudinski, J. B., S. E. Trumbore, E. A. hydrocarbons above a mid-latitude forest: Davidson , and E. Belk. 1997. biogenic emissions and seasonal Determination of organic carbon turnover concentration variations. PhD Thesis, rates at Harvard Forest, Massachusetts. In: Harvard. Agronomy Abstracts Annual Meeting. Goldstein, A. H., B. C. Daube, J. W. Munger, Gaudinski, J. B., S. E. Trumbore, E. A. and S. C. Wofsy. 1995. Automated in Davidson , and A. Richter. 2001. The age situ monitoring of atmospheric non- of fine-root carbon in three forests of the methane hydrocarbon concentrations and eastern United States measured by gradients. Journal of Atmospheric radiocarbon. Oecologia 129: 420-429. Chemistry 21: 43-59. Gaudinski, J. B., S. E. Trumbore, E. A. Goldstein, A. H., S. M. Fan, M. L. Goulden, J. Davidson , and S. Zheng. 2000. Soil W. Munger, and S. C. Wofsy. 1996. carbon cycling in a temperate forest: Emissions of ethene propene and 1-butene radiocarbon-based estimates of residence by a midlatitude forest. Journal of times, sequestration rates and partitioning Geophysical Research 101: 9149-9157. of fluxes . Biogeochemistry 51: 33-69. Goldstein, A. H., M. L. Goulden, J. W. Munger, George, L. 96. The understory as an ecological S. C. Wofsy, and C. D. Geron. 1998. filter. Ph.D. Thesis, Harvard. Seasonal course of isoprene emissions George, L. and F. A. Bazzaz. 2004. The from a midlatitude deciduous forest. herbaceous layer as a filter determining Journal of Geophysical Research 103: spatial patterns in forest regeneration. In 31045-31051. K. Jensen (Eds.), Oxford University Goldstein, A. H., C. M. Spivokovsky, and S. C. Press, U. K. (In Press). Wofsy. 1995. Seasonal variations of non- George, L. O. and F. A. Bazzaz. 1999. The fern methane hydrocarbons in rural New understory as an ecological filter: England: constraints on OH emergence and establishment of canopy concentrations in northern midlatitudes. tree seedings. Ecology 80: 833-845. Journal of Geophysical Research 100: George, L. O. and F. A. Bazzaz. 1999. The fern 21023-21033.

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150 1-24. McManus, and S. C. Wofsy. 1999. Nitric Hendricks, J. J. 94. Assessing the effects of acid and nitrogen dioxide flux nitrogen availability on fine root turnover measurements: a new application of and tissue chemistry in forest ecosystems. tunable diode laser absorption Ph.D. Thesis, University of New spectroscopy. SPIE 3758: 152-165. Hampshire. Hughes, L. and F. A. Bazzaz. 1997. Effect of Hendricks, J. J., J. D. Aber, K. J. Nadelhoffer, elevated CO2 on interactions between the and R. D. Hallett. 2000. Nitrogen western flower thrips, Frankliniella controls on fine root substrate quality in occidentalis (Thysanoptera: Thripidae) temperate forest ecosystems. Ecosystems and the common milkweed, Asclepias 3: 57-69. syriaca. Oecologia 109: 286-290. Hendricks, J. J., K. J. Nadelhoffer, and J. D. Hurst, J. M., D. J. Barket, O. Herrera-Gomez, T. Aber. 1993. The role of fine roots in L. Couch, P. B. Shepson, I. Faloona, D. energy and nutrient cycling. Trends in Tan, W. Brune, H. Westberg, B. Lamb, T. Ecology and Evolution 8: 174-178. Biesenthal, V. Young, A. H. Goldstein, J. Hendricks, J. J., K. J. Nadelhoffer, and J. D. W. Munger, M. A. Carroll, and T. Aber. 1997. A 15N tracer technique for Thornberry. 2001. Investigation of the assessing fine root production and nighttime decay of isoprene. Journal of turnover. Oecologia 112: 300-304. Geophysical Research 106: 335-24, 346. Hill, C. 97. The representation of categorical Jasienski, M., F. J. Ayala, and F. A. Bazzaz. ambiguity: a comparison of fuzzy, 1997. Phenotypic plasticity and probabilistic Boolean and index similarity of DNA among genotypes of an approaches in suitability analysis. Ph.D. annual plant. Heredity 78: 176-181. Thesis, Harvard. Jasienski, M. and F. A. Bazzaz. 1999. The Hirose, T., D. D. Ackerly, and F. A. Bazzaz. fallacy of ratios and the testability of 1996. CO2 and canopy development in models in biology. Oikos 84: 321-326. stands of herbaceous plants. Pp. 413-430 Jasienski, M., S. C. Thomas, and F. A. Bazzaz. In Ch. Körner and F. A. Bazzaz (Eds.), 1998. Blaming the trees: a critique of Carbon Dioxide, Populations and research on forest responses to high CO2. Communities. Academic Press , London. Tree 13: 427. Hirose, T., D. D. Ackerly, M. B. Traw, and F. A. Jenkins, J., J. Aber, and C. Canham. 1999. Bazzaz. 1996. Effects of CO2 elevation Hemlock woolly adelgid impacts on on canopy development in the stands of community structure and N cycling rates two co-occurring annuals. Oecologia 108: in eastern hemlock forest. Canadian 215-223. Journal of Forest Research 29: 630-645. Hirsch, A. I., J. W. Munger, D. J. Jacob, L. W. Jenkins, J. C., D. W. Kicklighter, and J. D. Aber. Horowitz, and A. H. Goldstein. 1996. 1999. Sources of variability in NPP Seasonal variation of the ozone production predictions at a regional scale: a efficiency per unit NOx at Harvard Forest, comparison using PnET-II and TEM 4.0 Massachusetts. Journal of Geophysical in northeastern forests. Ecosystems 2: Research 101: 12659-12666. 555-570. Holbrook, N. M. and M. A. Zwieniecki. 1999. Jenkins, J. C., D. W. Kicklighter, and J. D. Aber. Embolism repair and xylem tension: do 2000. Predicting the regional impacts of we need a miracle? Plant Physiology 120: increased CO2 and climate change on 7-10. forest productivity: a model comparison Holbrook, N. M., M. A. Zwieniecki, and P. J. using PnET-II and TEM 4.0. Pp. 383-423 Melcher. 2002. The dynamics of "dead" In R. Birdsey, J. Hom, and R. Mickler wood: maintenance of water transport (Eds.), Responses of Northern Forests to through plant stems. Integrative and Environmental Change. Springer-Verlag. Comparative Biology 42: 492-496. Johnson, T. C., E. T. Brown, J. McManus, S. Horii, C. V., M. S. Zahniser, D. D. Nelson, J. B. Barry, P. Barker, and F. Gasse. 2002. A

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152 Cultivation: Regional and Stand-Level disturbance in central New England, Constraints. In B. L. Turner, J. U.S.A. Ecoscience 5: 232-240. Geoghegan, and D. R. Foster (Eds.), Mack, R. N., D. Simberloff, W. M. Lonsdale, H. Integrated Land Change Science and Evans, M. Clout, and F. A. Bazzaz. 2000. Tropical Deforestation in Southern Biotic invasions: causes epidemiology, Yucatán: Final Frontiers. Oxford global consequences and control. Issues University Press, New York. in Ecology. Ecological Society of America Lefer, B. L., R. W. Talbot, and J. W. Munger. 5: 2-20. 1999. Nitric acid and ammonia at a rural Mack, R. N., D. Simberloff, W. M. Lonsdale, H. northeastern U.S. site. Journal of Evans, M. Clout, and F. A. Bazzaz. 2000. Geophysical Research 104: 1645-1661. Biotic invasions: causes epidemiology, Lerdau, M. T., J. W. Munger, and D. J. Jacob. global consequences and control. 2000. The NO2 flux conundrum. Science Ecological Applications 10: 689-710. 289: 2291. Magill, A. H. and J. D. Aber. 1998. Long-term Lewis, D. A., W. Garrison, E. Wommack, A. effects of chronic nitrogen additions on Whittemore, P. Steudler, and J. Melillo. foliar litter decay and humus formation in 1999. Influence of environmental forest ecosystems. Plant and Soil 203: changes on degradation of chiral 301-311. pollutants in soils. Nature 401: 898-901. Magill, A. H. and J. D. Aber. 2000. Dissolved Li, A., D. L. Godbold, G. M. Berntson, and F. organic carbon and nitrogen relationships A. Bazzaz. 1998. The dynamics of root in forest litter as affected by nitrogen production and loss in Betula papyrifera deposition. Soil Biology and Biochemistry seedlings in response to elevated CO2 and 32: 603-613. an aluminum pulse. Z. Pflanzenernähr. Magill, A. H. and J. D. Aber. 2000. Variation Bodenk. 161: 17-21. in soil net mineralization rates with Linkins, A. E., R. L. Sinsabaugh, C. M. dissolved organic carbon additions. Soil McClaugherty, and J. M. Melillo. 1990. Biology and Biochemistry 32: 597-601. Comparison of cellulase activity on Magill, A. H., J. D. Aber, G. M. Berntson, W. H. decomposing leaves in a hardwood forest McDowell, K. J. Nadelhoffer, J. M. and woodland stream. Soil Biology and Melillo, and P. A. Steudler. 2000. Long- Biochemistry 22: 423-425. term nitrogen additions and nitrogen Loiselle, B. A., Howell, C. A., Graham, C. H., saturation in two temperate forests. Goerck, J. M., Brooks, T., Smith, K. G., Ecosystems 3: 238-253. and Williams, P. H. 2003. Avoiding Magill, A. H., J. D. Aber, W. Currie, K. J. Pitfalls of Using Species Distribution Nadelhoffer, M. E. Martin, W. H. Models in Conservation Planning. McDowell, J. M. Melillo, and P. Steudler. Conservation Biology 17[6], 1591-1600. 2004. Ecosystem Response to 15 years of Louis, I., S. Racette, and J. G. Torrey. 1990. Chronic Nitrogen Additions at the Occurrence of cluster roots on Myrica Harvard Forest LTER, Massachusetts, cerifera L. (Myricaceae) in water culture USA. (submitted). in relation to phosphorus nutrition. New Magill, A. H., J. D. Aber, J. J. Hendricks, R. D. Phytologist 115: 311-317. Bowden, J. M. Melillo, and P. A. Steudler. Mabry, C., M. Jasienski, J. S. Coleman, and F. 1997. Biogeochemical response of forest A. Bazzaz. 1997. Genotypic variation in ecosystems to simulated chronic nitrogen Polygonum pensylvanicum: nutrient deposition. Ecological Applications 7: effects on plant growth and aphid 402-415. infestation. Canadian Journal of Botany Magill, A. H., M. R. Downs, K. J. Nadelhoffer, 75: 546-551. R. A. Hallett, and J. D. Aber. 1996. Mabry, C. and T. Korsgren. 1998. A permanent Forest ecosystem response to four years of plot study of vegetation and vegetation- chronic nitrate and sulfate additions at site factors fifty-three years following Bear Brooks Watershed, Maine, USA.

153 Forest Ecology and Management 84: gas exchange in five temperate deciduous 29-37. tree species grown in elevated CO2 Magill, A. M., J. D. Aber, K. N. Nadelhoffer, J. concentrations. Global Change Biology 2: M. Melillo, and P. Steudler. 2004. 25-34. Integrated ecosystem response to chronic McConnaughay, K. D. M., A. B. Nicotra, and F. nitrogen additions at the Harvard Forest: A. Bazzaz. 1996. Rooting volume, introduction and long-term data. Forest nutrient availability and CO2-induced Ecology and Management (Submitted). growth enhancement in temperate forest Maherali, H., E. H. DeLucia, and T. W. Sipe. tree seedlings. Ecological Applications 6: 1997. Hydraulic adjustment of maple 619-627. saplings to canopy gap formation. McDowell, W. H., W. S. Currie, J. D. Aber, and Oecologia 112: 472-480. Y. Yano. 1998. Effects of chronic Martin, M. E. 94. Measurements of foliar nitrogen amendment on production of chemistry using laboratory and airborne dissolved organic carbon and nitrogen in high spectral resolution visible and forest soils. Water, Air and Soil Pollution infrared data. PhD Thesis, University of 105: 175-182. New Hampshire. McDowell, W. H., A. Magill, J. A. Aikenhead- Martin, M. E. and J. D. Aber. 1990. The effect Peterson, J. D. Aber, J. Merriam, and S. of water content and leaf structure on the Kaushal. 2004. Effects of chronic estimation of nitrogen, lignin and cellulose nitogen amendment on dissolved organic content of forest foliage samples. Remote matter and inorganic nitrogen soil Sensing for the Nineties IGARSS: 24-28. solution. Forest Ecology and Management Martin, M. E. and J. D. Aber. 1990. Effects of (submitted). moisture content and chemical McGuire, A. D., D. W. Kicklighter, and J. M. composition on the near infrared spectra Melillo. 1996. Global climate change and of forest foliage. In: Proceedings of the carbon cycling in grasslands and conifer International Society for Optical forests. Pp. 389-412 In A. I. Breymeyer, Engineering Technical Symposium on D. O. Hall, J. M. Melillo, and G. Ĺgren Aerospace Sensing. (Eds.), Global Change: Effects on Martin, M. E. and J. D. Aber. 1997. Estimation Coniferous Forests and Grasslands. John of forest canopy lignin and nitrogen Wiley and Sons. concentration and ecosystem processes by McGuire, A. D., J. M. Melillo, A. Joyce, D. W. high spectral resolution remote sensing. Kicklighter, A. L. Grace, B. I. Moore, and Ecological Applications 7: 431-443. C. J. Vorosmarty. 1992. Interactions Martin, M. E. and J. D. Aber. 2000. Estimating between carbon and nitrogen dynamics in forest canopy characteristics as inputs for estimating net primary productivity for models of forest carbon exchange by high potential vegetation in North America. spectral resolution remote sensing. Pp. Global Biogeochemical Cycles 6: 101- 61-72 In H. Gholz (Eds.), The Use of 124. Remote Sensing in the Modeling of Forest McGuire, A. D., J. M. Melillo, and L. A. Joyce. Productivity at Scales from the Stand to 1995. The role of nitrogen in the the Globe. Kluwer Academic Publishers, response of forest net primary production The Netherlands . to elevated atmospheric carbon dioxide. Martin, M. E., S. D. Newman, J. D. Aber, and R. Annual Review of Ecology and Congalton. 1997. Determining forest Systematics 26: 473-503. species composition using high spectral McGuire, A. D., J. M. Melillo, D. W. resolution remote sensing data. Remote Kicklighter , and L. A. Joyce. 1995. Sensing of the Environment 65: 249-254. Equilibrium responses of soil carbon to McConnaughay, K. D. M., S. L. Bassow, G. M. climate change: Empirical and process- Berntson, and F. A. Bazzaz. 1996. Leaf based estimates. Journal of Biogeography senescence and decline of end-of-season 22: 785-796.

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ACKNOWLEDGEMENT OF SUPPORT

Research activities described in this booklet are supported in part by funds provided by the following sources:

Friends of the Harvard Forest Anonymous Donor John and Edith Downs Memorial Trust Golden Family Foundation Harvard University Joseph H. Clark Fund V. Kann Ramussen Foundation Charles H. Tozier Fund Massachusetts Environmental Trust A. W. Mellon Foundation Mount Everett Research and Protection Fund of the Southern Taconics Research and Conservation Center National Park Foundation National Park Service National Science Foundation, Programs in Biocomplexity in the Environment Digital Government Ecological Biology Cluster Ecosystems Studies Field Stations Information Technology Research Program Instrumentation and Instrument Development Long Term Ecological Research Research Experience for Undergraduates The Nature Conservancy Sweetwater Trust U. S. Department of Agriculture, Northeastern Area Federal Focus Funding U. S. Department of Energy National Institutes for Global Environmental Change

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