Carbon Dynamics in Terrestrial and Aquatic Ecosystems: Effects of Climate Change

Carbon dynamics in terrestrial and aquatic ecosystems: Effects of climate change

Workshop 12 – 13 November, 2007 Norsk Landbruksmuseum, Norwegian University of Life Sciences, Aas, Norway Organization committee:

Dept. of Plant and Jan Mulder Environmental Sciences, Norway [email protected] UMB Dept. of Plant and Vegard Environmental Sciences, Norway [email protected] Martinsen UMB

Scientific committee:

Dept. of Plant and Jan Mulder Environmental Sciences, Norway [email protected] UMB Dept. of Ecology and Natural Mikael Ohlson Resource Management, Norway [email protected] UMB Dept. of Ecology and Natural Terje Kristensen Resource Management, Norway [email protected] UMB Norwegian Forest and Holger Lange Norway [email protected] Landscape Institute Department of Geosciences, Per Aagaard Norway [email protected] University of Oslo

2 Agenda:

Monday 12 November 0900-0910 Knut Hove UMB Welcome 0910-0915 Jan Mulder IPM, UMB 0900-1135 Research presentations and discussion: Chair: Arne Stuanes (IPM, UMB) Dan Berggren, SLU, 0915-1000 Presentation Carbon sequestration in Swedish forest soils invited Uppsala speaker Terje 1000-1020 Presentation INA, UMB Linking belowground Carbon with LiDAR Kristensen 1020-1035 Coffee

Carbon sequestration in soil; the importance of 1035-1055 Presentation Lars Bakken IPM, UMB Occam's razor in modeling and experiments

Susanne Influence of climate change on growth and 1055-1115 Presentation Eich- IPM, UMB carbon sequestration potential of bioenergy crops Greatorex General 1115-1135 Presentation discussion 1135-1235 Lunch Chair: Holger Lange (Norwegian Forest and 1235-1720 Research presentations and discussion: Landscape Institute) Frank Hagedorn, Climate change at the alpine treeline; impacts of 1235-1320 Presentation invited WSL, elevated CO2 and warming on carbon cycling. speaker Switzerland Effects of sheep grazing on levels of carbon and Vegard 1320-1340 Presentation IPM, UMB nitrogen in soil and surface water in alpine areas Martinsen of Southern Norway

Carbon Pool and Potential Carbon Sequestration Ambachev D 1340-1400 Presentation IPM, UMB of the Land use Types in Central Rift valley of S. Wele Ethiopia 1400-1415 Coffee Mats Nilsson, Carbon dynamics in mires - in perspective of a 1415-1500 Presentation invited SLU, Umeå changing climate. speaker 1500-1520 Presentation Peter Dörsch IPM, UMB CH4 fluxes in a stratified boreal landscape 1520-1535 Fruits Michael Hauhs, Complex or Interactive? New Perspectives in 1535-1620 Presentation invited BITÔK, Ecological Modelling speaker Bayreuth Bharat Modeling soil organic carbon stocks and changes 1620-1640 Presentation IPM, UMB Shrestha in a mountain watershed of Nepal Growth in situ of Lobaria spp, area 1640-1700 Presentation Per Larsson INA, UMB measurements with digital photography Norwegian Holger Lange Forest and General 1700-1720 and Jan Landscape discussion Mulder Institute, IPM (UMB) Workshop 1830 dinner

3 Tuesday 13 November 0900-0910 Announce-ments Jan Mulder IPM, UMB

0910-1210 Research presentations and discussion: Chair: Gunhild Riise (INA, UMB)

Carbon, climate change, and why Chris Evans, invited CEH, 0910-0955 Presentation sulphur and nitrogen make things speaker Bangor, UK more complicated Precipitation experiments in small 0955-1015 Presentation Ståle Haaland IPM, UMB catchments in a montane area in southern Norway Dept. of Linking surface water NO3 and 1015-1035 Presentation Anne Merete Sjøeng Bio., UiO TOC; results from a N addition and NIVA field experiment Aleksandra Climate change and 1035-1055 Presentation IPM, UMB Romarheim eutrophication process in lakes 1055-1110 Coffee Long-term trends in DOC - a 1110-1130 Presentation Heleen de Wit NIVA response to reduced acid deposition Dept. of Causes for the increasing trends 1130-1150 Presentation Rolf D. Vogt Chem., UiO in DOC and colour

General 1150-1210 Gunhild Riise IPM, UMB discussion 1210-1310 Lunch Group Discussions in small 1310-1500 discussions groups Discussion leader: 1500-1530 Panel discussion INA, UMB Mikael Ohlson

1530-1545 Summing up Jan Mulder

4 Participants:

Participants Institute E-mail: Department of Andersen Tom Biology, University of [email protected] Oslo Department of Auterives Chrystelle Biology, University of [email protected] Oslo Dept. of Plant and Bakken Lars Environmental [email protected] Sciences, UMB Dept. of Plant and Bleken Marina Azzaroli Environmental [email protected] Sciences, UMB Swedish University of Berggren Dan Agricultural Sciences, [email protected] Uppsala Dept. of Ecology and Bergseng Even Natural Resource [email protected] Management, UMB Norwegian Forest and D. Eldhuset Toril [email protected] Landscape Institute Dept. of Plant and D. Wele Ambachev Environmental [email protected] Sciences, UMB Norwegian Institute for de Wit Heleen [email protected] , Water Research Dept. of Plant and Dörsch Peter Environmental [email protected] Sciences, UMB Dept. of Plant and Eich-Greatorex Susanne Environmental [email protected] Sciences, UMB Centre for Ecology Evans Chris and Hydrology, [email protected] Bangor, UK Dept. of Plant and Fjeld Tove Environmental [email protected] Sciences, UMB Dept. of Ecology and Gauslaa Yngvar Natural Resource [email protected] Management, UMB

Swiss Federal Institute Hagedorn Frank of Forest, Snow and [email protected] Landscape Research

Ecological Modelling, Hauhs Michael [email protected] University of Bayreuth Hove Knut Central administration [email protected] Norwegian Forest and Hylen Gro [email protected] Landscape Institute Dept. of Plant and Haaland Ståle Environmental [email protected] Sciences, UMB Dept. of Plant and Islam Nazrul Environmental [email protected] Sciences, UMB Norwegian Institute for Jentzen Anna [email protected] Water Research

5 Participants Institute E-mail: Dept. of Plant and Jibat Girma Abera Environmental [email protected] Sciences, UMB Norwegian Forest and Kjønås Janne [email protected] Landscape Institute Dept. of Ecology and Kristensen Terje Natural Resource [email protected] Management, UMB Dept. of Plant and Kynding Borgen Signe Environmental [email protected] Sciences, UMB Norwegian Forest and Lange Holger [email protected] Landscape Institute Department of Larsen Søren Biology, University of [email protected] Oslo Dept. of Ecology and Larsson Per Natural Resource [email protected] Management, UMB Dept. of Plant and Martinsen Vegard Environmental [email protected] Sciences, UMB Dept. of Ecology and Meen Eivind Natural Resource [email protected] Management, UMB. Dept. of Plant and Mulder Jan Environmental [email protected] Sciences, UMB Norwegain Forest and Nilsen Petter [email protected] Landscape Institute Swedish University of Nilsson Mats Agricultural Sciences, [email protected] Umeå Dept. of Ecology and Næsset Erik Natural Resource erik.næ[email protected] Management, UMB. Dept. of Ecology and Ohlson Mikael Natural Resource [email protected] Management, UMB Norwegian Institute for Agricultural and Rasse Daniel [email protected] Environmental Research Dept. of Plant and Riise Gunhild Environmental [email protected] Sciences, UMB Dept. of Plant and Romarheim Aleksandra Environmental [email protected] Sciences, UMB Dept. of Plant and Semb Vestgarden Live Environmental [email protected] Sciences, UMB Dept. of Plant and Shrestha Bharat Environmental [email protected] Sciences, UMB Dept. of Plant and Singh Bal Ram Environmental [email protected] Sciences, UMB

6 Participants Institute E-mail: Department of Biology, UiO and Sjøeng Anne Merete [email protected] Norwegian Institute for Water Research Dept. of Plant and Sogn Trine Environmental [email protected] Sciences, UMB Dept. of Ecology and Solhaug Knut Asbjørn Natural Resource [email protected] Management, UMB Norwegian Institute for Agricultural and Stolte Jannes [email protected] Environmental Research Dept. of Plant and Stuanes Arne Environmental [email protected] Sciences, UMB Dept. of Plant and Sørensen Rolf Environmental [email protected] Sciences, UMB Dept. of Plant and Tau Strand Line Environmental [email protected] Sciences, UMB Dept. of Plant and Tiwari Krishna Environmental [email protected] Sciences, UMB Department of Vogt Rolf D. Chemistry, University [email protected] of Oslo, Norwegian Institute for Wright Richard F. Water Research [email protected] Dept. of Plant and Environmental Wu Yijie Sciences, UMB/ [email protected] Norwegain Forest and Landscape Institute University of Oslo, Xie Ruikai Department of [email protected] Chemistry Department of Aagaard Per Geosciences, [email protected] University of Oslo

7 Abstracts:

Carbon sequestration in Swedish forest soils

Dan Berggren Kleja1, Magnus Svensson2, Per-Erik Jansson2 and Mats Olsson3

1Department of Soil Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden

2Department of Land and Water Resources Engineering, Royal Institute of Technology, Stockholm, Sweden

3Department of Forest Soils, Swedish University of Agricultural Sciences, Uppsala, Sweden

We present an integrated analysis of organic carbon (C) pools in soils and vegetation, within- ecosystem fluxes and net ecosystem exchange (NEE) in three 40-year old Norway spruce stands along a north-south climatic gradient in Sweden, measured 2001-2004. A process-orientated ecosystem model (CoupModel), previously parameterised on a regional dataset, was used for the analysis. Pools of soil organic carbon (SOC) and tree growth rates were highest at the southernmost site (1.6 and 2.0-fold, respectively). Tree litter production (litterfall and root litter) was also highest in the south, with about half coming from fine roots (< 1 mm) at all sites. However, when the litter input from the forest floor vegetation was included, the difference in total litter input rate between the sites almost disappeared (190-233 g C m-2 yr-1). We propose that a higher N deposition and N availability in the south result in a slower turnover of soil organic matter than in the north. This effect seems to overshadow the effect of temperature. At the southern site, 19% of the total litter input to the O horizon was leached to the mineral soil as dissolved organic carbon, while at the two northern sites the corresponding figure was approx. 9%. The CoupModel accurately described general C cycling behaviour in these ecosystems, reproducing the differences between north and south. The simulated changes in SOC pools during the measurement period were small, ranging from -8 g C m-2 yr-1 in the north to +9 g C m-2 yr-1 in the south. In contrast, NEE and tree growth measurements at the northernmost site suggest that the soil lost about 90 g C m-2 yr-1.

References Berggren Kleja D., Svensson M., Majdi,H., Jansson, P-E., Langvall, O., Bergkvist, B., Johansson, M-B., Weslien, P., Lindroth, A & Ågren, G.I. 2007. Pools and fluxes of carbon in three Norway spruce ecosystems along a climatic gradient in Sweden . Biogeochemistry (in press)

Svensson M., Jansson P.-E., Berggren Kleja D. 2007. Soil C sequestration in spruce forest ecosystems along a Swedish transect based on current conditions. Biogeochemistry (in press)

8 Linking belowground Carbon with LiDAR

Terje Kristensen, Dep. of ecology and natural resource management (INA) Norwegian University of Life Sciences (UMB).

Carbon stored belowground can be characterized by large heterogeneity, both in biochemical attributes and spatial distribution. To understand the C dynamics in a forest ecosystem it is necessary to disclose and quantify this heterogeneity. Until now it has been almost impossible to get high definition information for large geographical areas, because conventional methology is too expensive to bring forward the data needed. As there is an increased international interest in C accounting in forest ecosystems, there is a need for efficient methods to estimate the above- as well as the below-ground biomass components of the trees over large areas. LiDAR (Light Detection and Ranging) enables us to draw a 3-dimensional picture of the structure of trees and ground. LiDAR has proofed to be an accurate technology for precise estimation of aboveground biomass and C stocks in boreal forests. Next step is to study the relationship between the aboveground biomass and belowground C. The relationship between the biomass that can be derived from using LiDAR and the amount of C in the soil might seem delicate, but new research results shows that the relationship between the photosynthesis in the aboveground biomass and the biological activity in the soil community is much more directly linked to each other than believed before. On behalf of this strong connection and the fact that the respiration from the soil communities regulates the processing of soil C, e.g. if the soil saves or releases C, is my hypothesis that LiDAR data could be used to quantify the amount of C in forest soil.

9 Carbon sequestration in soil; the importance of Occam's razor in modelling and experiments

Lars Bakken, Dept. of Plant and Environmental Sciences, Norwegian University of Life Sciences (UMB).

The carbon mineralization in soil is a very complex process, but can be modelled reasonably well with simple first order decay models with some modifications to include the process of "stabilization", i.e. transfer of fractions of the reactive compounds to stable pools.

Experiments should be guided by such models to zoom in on critical factors governing the soil organic carbon dynamics in soil. Occams razor should be "used" to avoid complication of the models unless strongly supported by residuals. Examples are variable Q10 values for different reactions and different humification coefficients for root- versus shoot-material, "priming" of mineralization by soil tillage and input of fresh organic materials.

Global warming has fostered much headless and futile experimentation, and ditto interpretations. Useful research schemes may involve mechanistic/molecular approaches to improve our understanding of the stabilization experiment, but will not necessarily provide a basis for improvement of predictive models.

10 Influence of climate change on growth and carbon sequestration potential of bioenergy crops

Susanne Eich-Greatorex, Dept. of Plant and Environm. Sciences, Norwegian University of Life Sciences (UMB).

Bioenergy has a large potential for reducing use of fossil fuels both worldwide and in Norway. With increasing temperatures due to climate change it is predicted that Northern Europe will increase its importance for producing food and energy crops during the course of the 21st century. For Norway with its limited area that is available for crop production, it will be important to know which energy crops are the most productive in terms of yield per area while at the same time considering the different potential of these crops with respect to C sequestration. The main objective of this project therefore aims at developing a modelling tool to predict the consequences of climate change on the yields and C sequestration potential of different energy crops in different climatic and geographical regions of Norway. The energy crop systems include agricultural, traditional forest and short- rotation forest systems. The effects of climate change are to be evaluated based on sustainability principles. Existing data from field experiments in Norway, Sweden and Denmark will be collected in a database on yield, carbon binding and soil characteristics of different land use systems for calibration of the model. Due to the diversity of the crops to be simulated, several existing models designed for different land use systems are being considered. A model originally designed for forest systems will also be tried in an agricultural system or vice versa.

11 Climate change at the alpine treeline: Impacts of elevated CO2 and warming on carbon cycling

Frank Hagedorn, Swiss Federal Institute of Forest, Snow and Landscape Research (WSL), Zürcher Str. 111, CH-8903 Birmensdorf, Switzerland

The ongoing increase in atmospheric CO2 affects ecosystem functioning either directly through its effects on photosynthesis or indirectly by climatic warming. At the Swiss alpine treeline, we are assessing ecosystem responses to a seven-year free air CO2 enrichment experiment (FACE) and a 13 one-year experimental soil warming of 3°C. The added CO2 contains another  C signature than normal air, which allows to trace the new carbon through the plant and soil system and to gain insight into carbon cycling at the treeline. Our results show that CO2 enrichment stimulated photosynthetic CO2 uptake by pine and larch by 20 to 50% throughout the years. The growth response was, however, species and time dependent with larch profiting initially (up to 35%) and pine and dwarf shrubs showing no response. Soil respiration was about 30% greater at the higher CO2 level, suggesting that elevated CO2 increased C cycling rates but not C storage which would be relevant for C sequestration. The 13C tracing revealed that a large fraction was rapidly cycling through the plant and soil system: 70% of assimilated carbon by plants was allocated to the belowground, from which more than 80% was respired back to the atmosphere. Only 1-3% of the C allocated to the belowground was leached as DOC from the organic layer, implying that DOC consists primarily of relative old C. Experimental warming for one year affected C fluxes differently with soil respiration being most responsive, plant growth showing a slight stimulation and DOC leaching not responding.

12 Effects of sheep grazing on levels of carbon and nitrogen in soil and surface water in alpine areas of Southern Norway

Vegard Martinsen, Department of Plant and Environmental Sciences, Norwegian University of Life Sciences (UMB).

Much research has been done to determine effects of climate change and grazing on carbon and nitrogen dynamics. Depending on site fertility, levels of grazing pressure and amplitude of climatic changes, ecosystem impact may vary considerably. Increases in CO2 concentration leading to a warmer climate may increase carbon sequestration (i.e. increased soil carbon stocks) if not constrained by availability of nutrients or offset by increased decomposition. This may lead to structural and functional changes in vegetation and thereby both directly and indirectly affecting soil processes controlling carbon and nutrient availability. Herbivory is reported to affect productive and unproductive ecosystems differently depending on grazing intensity, grazing frequency and length of grazing season. These direct consequences of grazing activity may indirectly lead to positive or negative feedback mechanisms controlling ecosystem structure and function.

In the last decades a woody encroachment has been observed in mountainous areas in Norway. This has been attributed to combined effects of changes in land use and climate. Studies have shown positive correlations between amount of DOC in surface water and factors such as soil carbon stocks, which is highly affected by vegetation cover. It has been reported increased levels of nitrate draining highly grazed areas, indicating nitrogen saturation or changed hydrological pathways (e.g. reduced infiltration rate and increased surface runoff). Little has been done to determine effects of changes in land use patterns in Norway.

Even though we are starting to understand some of the biogeochemical changes caused by changes in climate and land use, there is still a lack of knowledge regarding integrated effects in high latitude ecosystems. Few studies have looked at the combined effect of changes in these environmental drivers. The aim of this talk is to present the sites and methodology that will be used determining impacts on above ground and below ground processes controlling levels of carbon and nitrogen as affected by different grazing pressures of sheep and altitudinal differences in temperature and moisture. Hypothesis will be presented and discussed.

13 Carbon Pool and Potential Carbon Sequestration of the Land use Types in Central Rift valley of S. Ethiopia

Ambachev D Wele, Dept. of Plant and Environmental Sciences, Norwegian University of Life Sciences (UMB).

Global warming caused by the build-up of greenhouse gases (GHGs) is threatening mankind. The major causes for the efflux of these gases are fossil fuel combustion, deforestation, and land use changes around the world. Poor land cover, overgrazing and mismanagement of agricultural lands are strongly correlated with the loss of soil organic matter, C pool and many essential nutrients for plant growth. Decrease in plant productivity may lead to reduction in soil C sequestration and increase in net emission of GHGs. Occurrence of these processes in an environment of limited resources and in areas where introduction of sustainable technologies and practices are not propitious, resource degradation and the vicious cycle of poverty is exacerbated. In Ethiopia, the forest cover is reduced from 16% in the early 1950s to 2.8 % in the 1990s resulting in rural poverty and underdevelopment. The Rift Valley is characterized with diverse climatic conditions, vegetation cover and agricultural land use systems. Clearing of woodlands and overgrazing are rampant. Reduction in soil productivity and desertification are the main threats to natural resources. The C sequestration potential of the vegetation and other land use systems in the study area has not yet been assessed. Therefore, this study aims at investigating the effect of vegetation management and land uses on C sequestration to restore degraded soils in the central Rift Valley of southern Ethiopia.

14 Carbon dynamics in mires - in perspective of a changing climate

Mats Nilsson, Department of Forest Ecology and Management, SLU, Umeå, Sweden.

Since the last deglaciation mires in the northern hemisphere has accumulated organic carbon and emitted methane to the atmosphere. Based on extensive data from peat cores the global estimate of the Holocene apparent carbon accumulation rate centre around 15-30 g C m-2 yr-1. More detailed studies of peat cores from the more recent Holocene time period (~ 500 – 2000 BP) though indicate a decline in apparent C-accumulation. Some data on the contemporary land-atmosphere exchange of CO2 (NEE) as well as theories on both mire development and their response to a changing climate has also resulted in that the current role of mires as a net carbon sink has been questioned. A rigorous evaluation of the contemporary mire C-balance requires that all significant C-fluxes are considered. The net ecosystem carbon balance (NECB), including all C-fluxes, of mires is dominated by three flux components: the land-atmosphere exchange of 1) CO2 (NEE), and 2) methane, and 3) the runoff export of carbon. Data on the annual C-flux for each flux component are relatively frequent. However, data based on full year measurements are still limited. Even more important is that simultaneous full year measurements of all significant flux components from the same mire are even more restricted. Estimates of the contemporary annual NEE based on continuous Eddy-Covariance measurements exist from about ten sites in the northern hemisphere. The estimated annual NEE -2 -1 constitute in all cases a net uptake ranging between ≈ 20 - 80g CO2-C m yr . This annual net uptake of CO2-C from the atmosphere is though counterbalanced by loss through methane emission and water runoff export of C. The emission of methane range from about zero in “dry” ombrogenic -2 -1 mires (bog) to > 30 g CH4-C m yr from more “wet” minerogenic mires (fen). The runoff-C is comprised by total organic carbon (TOC) > dissolved inorganic carbon (DIC) + dissolved CO2 >> -2 CH4. The annual export of the major component TOC from mires varies between ~ 5 g – 25 C m yr-1. The relative importance of each of the C-flux components though varies most substantially depending on mire type and climatic regions. Also the climatic drivers for each C-flux component are most different. The effect of a changing climate on the mire net ecosystem carbon balance (NECB) might therefore be quite different depending on mire type and climatic region. Published data on multi year measurements of all flux components exists, to my knowledge, only from two mires, one ombrotrophic mire (bog) in southern Canada and one minerogenic mire (fen) in northern Sweden. Both mires constituted net carbon sinks, comparable in size to the long term average.

15 Exploring CH4 fluxes in a stratified boreal landscape

P. Dörsch 1, H. Lange2, C. Auterives3 and L. Bakken1

1 Dept. of Plant and Environmental Sciences, Norwegian University of Life Sciences (UMB). 2 Norwegian Institute of Forest and Landscape 3 Department of Biology, University for Oslo

A significant part of the boreal landmass is covered by poorly drained soils which act as long-term sinks for atmospheric carbon and net source for methane (CH4). It is unknown how changes in climate will affect the balance between organic matter storage and CH4 source strength; hydro- climatic changes affect both C sequestration through changes in productivity and decomposition and CH4 emission through changes in substrate quality and hydrological status. To advance our understanding of boreal responses to future climate change, we need to study emergent biogeochemical patterns in complex landscapes and to delineate the mechanisms that drive such changes at multiple scales. 2 Small-scale variability of CH4 emission rates was studied by chamber methods (0.07 – 1 m ) in a highly stratified mountainous landscape within the Langtjern watershed in Buskerud county, Southern Norway (60o22’ N 9o39’E, 510-750 m, 3oC, 850 mm). The watershed is characterized by mostly unproductive, old-growth Scots pine forest interspersed with peatlands covering ca. 30% of the area. Deep peat (> 3 m) is encountered in depressions, floodplains and in riparian zones. Shallower peat (< 1m) is found on gentle sloping food hills connecting the deeper peatlands along hydrological drainage networks. Typical peatland types are forested swamps with heath-dominated transition zones, Sphagnum-Carex lawns and hummocky fens. The latter are characterized by microtope complexes consisting of hummocks, hollows, strings and pools. We report ongoing attempts to characterize spatio-temporal CH4 emission patterns in this landscape and outline synoptic approaches based on ‘emerging technologies’ such as ground penetrating radar, remote imagery and molecular biology, to develop proxies for biogeochemical settings in general and CH4 fluxes in particular. The overall goal of this approach is to improve quantification of gas exchange between biosphere and atmosphere in complex landscapes.

16 Complex or Interactive? New Perspectives in Ecological Modelling

Michael Hauhs, Ecological Modelling University of Bayreuth.

Modelling offers two perspectives at environmental systems and ecosystems. The first one originated from Newtonian physics and is based on the theory of dynamic systems. Its central physical notion is that of state. This first approach is widespread among environmental modellers and is sometimes even identified with the scientific method as such. The second (new) approach has recently been derived within computer science. Its central notions are behaviour and interaction, which can be implemented with today’s computers. The notion of interactive computation extends the physical notion of functions into the realm of decision making, e.g. in a growing organism. Difficulties and limits of ecological modelling have often been described as resulting from the high complexity of these systems. Such an interpretation can now be challenged with the view, that principle limits may be linked with the interactive nature of Life rather than with its complexity. The alternate perspectives will be illustrated in an example from hydrology.

17 Modeling Soil Organic Carbon Stocks and Changes in a Nepalese Watershed

B. M. Shrestha1, S. Williams2, M. Easter2, K. Paustian2, B. R. Singh1*

1 Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, PO Box 5003, 1432 ÅS, Norway

2 The Natural Resources Ecology Laboratory, Colorado State University, Fort Collins, CO 80523- 1499, USA

* Corresponding author: Email: [email protected], Phone +47 6496 5564, Fax +47 6496 5601

Land use, land use change and forestry activities play an important role in determining whether the soil is a sink or source of atmospheric carbon dioxide (CO2). Effect of Land use change on climate change in many developing countries is receiving greater attention. We studied changes in soil organic carbon (SOC) pool over 100 years (1950 – 2050) under managed forest (DS), rain fed upland (Bari) and irrigated low land (Khet) of Pokhare Khola, a mid-hill watershed of Nepal, by using Century C model. The modelled temporal blocks of 1950-1970, 1971-1990 and 1991-2004 were based on the history of land use changes in the study area and the projection was done for the period 2005-2050. The model was calibrated and parameterized on the basis of biophysical and weather data of the watershed. Field work was done in September/October 2004. Historic carbon pool data was calculated following IPCC guideline for year 1976 and 1989. The Century C model performed well in its representation of the effect on SOC of various land management systems in Pokhare Khola watershed. Model results underscored the human impacts on the system. There was dramatic loss of SOC due to the removal of tree biomass in the first temporal block (1950-1970). However, it has been shown that partial recovery of lost SOC is possible through better forest management, especially if erosion is abated. In the cultivated land we found better recovery by addition of farm yard manure and fertilizer. In all the land use systems, the SOC recovery was lower under climate change scenario than under prevailing climate.

Key words: Century C model, Climate Change, Land Use Change, Mountain Watershed, Nepal, SOC pool

18 Growth in situ of Lobaria spp, area measurements with digital photography.

Per Larsson, Dept. of Ecology and Natural Resource Management, Norwegian University of Life Sciences.

The growth of Lobaria pulmonaria and L. scrobiculata is quantified in situ on small twigs of Picea abies in boreal rain forests in Nord-Trøndelag, middle Norway. Area growth of individual juvenile thalli will be monitored throughout a two years period by means of repeated digital photography. In addition, the first appearance and enlargement of surface areas devoted for vegetative reproduction propagules will be recorded. Size-dependent growth curves and onset of reproductive stage allow as assessment of the generation time under natural conditions. A similar study of the in situ growth of L. pulmonaria on trunks of Populus tremula is conducted in southeast Norway and will be compared with the study on twigs in Nord-Trøndelag. Methodology and some data for the first recording interval will be presented.

19 Carbon, climate change, and why sulphur and nitrogen make things more complicated

Chris Evans, Centre Ecology Hydrology, Bangor, UK.

Peatlands and other organic-rich soils contain large stores of carbon. Much recent work has suggested that soils in northern temperate and boreal ecosystems may be highly sensitive to climate change, either reducing their current role as a carbon sink, or converting them into a carbon source. This would represent a positive climate change feedback, with potentially severe consequences. In the UK, long-term data showing increases in surface water dissolved organic carbon (DOC) concentrations, and apparent decreases in soil C stocks, have been taken as evidence that these positive climate-change feedbacks are already occurring. This presentation will review this evidence, taking into account some of the other anthropogenic factors influencing carbon cycling in the UK and in other industrialised areas of the world. It is argued that perturbations to other biogeochemical cycles, notably sulphur and nitrogen, may be having a significant impact on carbon cycling, that changes in these cycles may help to explain observed trends. The influence of these other pollutants needs to be taken fully into account if environmental change in terrestrial and aquatic ecosystems is to be correctly attributed, climate change impacts accurately predicted, and appropriate policies applied to protect these ecosystems in future.

20 Precipitation experiments using small catchments in a montane heathland area in Southern Norway

Haaland S.1*, Austnes K.1, Kaste Ø.2, Mulder J.1, Riise G.1, Semb Vestgarden L.1, Stuanes A.1 1Norwegian University of Life Sciences, Department of Plant- and Environmental Sciences, P.O. Box 5003, NO-1432 Ås, Norway 2Norwegian Institute for Water Research, Televeien 3, NO-4879 Grimstad, Norway

Projected changes in climate in Southern Norway include increases in summer and autumn precipitation. This may affect the production and leaching of dissolved organic matter (DOM) from soils. Effects of experimentally added extra precipitation (10 mm week-1) to small headwater catchments in a montane heathland landscape in southern Norway (59°0´N, 550 – 600 m a.s.l.) on concentrations and fluxes of total organic carbon (TOC) and total organic nitrogen (TON) in runoff were assessed. Experimental manipulation was done during the growing season of three years (2004 – 2006). Episodic changes in TOC and TON concentrations occurred, but in general extra precipitation did not have a significant effect on the average TOC and TON concentrations in runoff. Hence, fluxes of TOC and TON increased almost proportionally with water fluxes. This suggests that a store of accumulated TOC and TON in catchment soils buffers the concentration of DOM in runoff. Pronounced droughts did not occur during the 3-year ecosystem manipulation period. Effects of relatively short drought episodes on TOC and TON fluxes in runoff from the reference catchments at Storgama are small.

21 Linking surface water NO3 and TOC; results from a N addition field experiment.

Anne Merete Smelhus SJØENG 1 ([email protected]) Dag Olav HESSEN 2 ([email protected]) Brit Lisa SKJELKVÅLE 1 ([email protected]) Søren Larsen 2 ([email protected]) Berit Kaasa 2 ([email protected])

1. Norwegian Institute for Water Research, P.O. 173 Kjelsås, N-0411 Oslo, Norway 2. The University for Oslo, Section of Marine Biology and Limnology, Department of Biology, P.O. Box. 1064, Blindern, N-0316 Oslo, Norway

Recent studies have shown an inverse relationship between dissolved organic carbon (DOC) and nitrate in surface water (see fig 1, Skjelkvåle et al., 1998), and a causal relationship between DOC and nitrate has been suggested (Goodale et al., 2005). In previous field manipulation experiments chronic N addition to (the NITREX project, Moldan et al., 2006 In press) or N removal from (the RAIN project, Wright et al., 1993) atmospheric deposition of these catchments did not cause any changes in DOC leaching from the catchment soil to surface water, thus the causal link in soils does not seem to be supported by empirical evidence. To test whether the observed inverse relationship between DOC and nitrate in surface water is due to processes within the water column, a field manipulation experiment was conducted in small humic lakes from June to November 2005. We hypothesized that N addition to humic lakes with low nutrient (e.g. nitrogen and phosphorus) content would stimulate bacterial production, hence resulting in an increased bacterial consumption of DOC and burn-off to CO2. If this actually would occur, we would expect a stabilization of the DOC concentrations during fall, rather than an increase as normally is observed in these lakes. Two small humic lakes were manipulated; one by adding nitrogen (NaNO3) and the other by adding nitrogen (NaNO3) + phosphorus (NaH2PO4). Three other humic lakes in the same area (<1 km apart) were chosen as controls. The lakes were sampled daily the first week after manipulation, then approximately weekly for about nine weeks. Results indicate that primary production (measured as chlorophyll a) increased more than the bacterial consumption of DOC, particularly in the N+P added lake.

Hardangervidda Femundsmarka 200 Rondane l

/ 150 N

N 100 Figure 1 Relationship between TOC and NO - concentrations 50 3 in mountain lakes (Skjelkvåle et al., 1998) 0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 TOC mg C/l

References Goodale, C.L., Aber, J.D., Vitousek, P.M. & McDowell, W.H. 2005. Ecosystems 8: 334-337. Moldan, F., Kjønaas, J.O., Stuanes, A. & Wright, R.F. 2006. Environmental Pollution xx: 1-11.Skjelkvåle, B. L. & Henriksen, A. 1998. NIVA report LNO 3895-98, 48pp. In Norwegian. Wright, R.F., Lotse, E. & Semb, A. 1993. Canadian Journal of Fisheries and Aquatic Sciences 50: 258-268.

22 Climate change and eutrophication process in lakes

Aleksandra Romarheim, Dept. of Plant and Environmental Sciences, Norwegian University of Life Sciences (UMB).

Enrichment of nutrients (eutrophication) in freshwater ecosystems enhances the primary production which seriously might affect the biogeochemical cycling of several elements. Oxygen depletion and changes in biodiversity with frequent blooms of blue green bacteria are consequences that might occur. Many shallow temperate lakes, such as the eutrophic lake Årungen, show a delay in the recovery process although several countermeasures have been made to reduce the external loading of nutrients, such as improved agricultural practices, treated sewage systems, construction of wetlands and other abatement strategies that reduce loss of phosphorus transported with eroded particles from the catchment. Lately, lots of attention has been given to climate changes and its impact on lake ecosystems. Increased precipitation and warming can change the seasonal availability of nutrients and thus the seasonality of the lake phytoplankton.

23 Drivers of long-term DOC trends in surface waters: climate or deposition?

Heleen de Wit, Norwegian Institute for Water Research (NIVA), Gaustadalléen 21, N-0349 Oslo, Norway [email protected], +47 9543 4360

Lake and stream water in glaciated landscapes across substantial areas of North America and northern and central Europe has become enriched in dissolved organic carbon (DOC) over the past two decades. Hypotheses about underlying causes include climate-change driven changes in temperature and precipitation and changes in acid deposition. Time series of DOC are analysed using step-wise regression to test various hypotheses on controls of DOC trends. First, an assessment of time series from over 500 acidification- sensitive sites in North America and northern Europe shows that the tendency for DOC increases in most regions between 1990 and 2004 can be explained by changes in the acid anion concentration of atmospheric deposition. DOC concentrations have increased proportionally with the decline both in anthropogenic sulphur, and, in some regions, seasalt deposition. This analysis is based on statistical correlation of annual mean element concentrations. Second, an analysis of time series of weekly DOC in 3 acid-sensitive catchments in Norway shows that seasonal variation in DOC is primarily climatically controlled, while acid deposition explains the long term increase in DOC. Increased humic charge and reduced ionic strength – both increasing organic matter solubility – are proposed as mechanistic explanation for the statistical relation between reduced acid deposition and increased DOC. Further reduction of atmospheric deposition will be limited suggesting that future increases in DOC will level off. In coast-near areas, DOC is likely to be impacted by seasalt deposition that fluctuates with the North Atlantic Oscillation index (NAOi). GCMs predict a higher frequency of positive NAOi under climate change, possibly correlated with more seasalt deposition.

24 Causes for the increasing trends in DOC and colour

Rolf D. Vogt; Dept. of Chemistry, University of Oslo.

The concentration of dissolved natural organic matter (DOM) and water colour of lakes and streams in Europe and North America, which have been suffering from acid rain, have showed an unprecedented increase during the last two decades. Several hypotheses to explain this increase have been put forward. This presentation argues that the strong decrease in aluminium concentrations, due to reduced acid deposition, has acted as a strong governing factor for the increased amount of aquatic DOM and specially colour in surface waters in Norway. Aluminium is a powerful precipitator and flocculent of DOM, particularly its more coloured hydrophobic fraction. This conceptual hypothesis is empirically substantiated by a multivariate statistical analysis of monitoring data on surface water chemistry in water courses that have been to varying degree exposed to acid rain in Norway and the UK. Inorganic labile aluminium (Al_i ) and total organic carbon (TOC) show strong opposite scores along the first two principal components (PC) in principal component analysis (PCA) at the 4 most acidified of the 10 monitored water courses in Norway. In addition strong negative correlations were found along either the first or second PC at 5 of the other sites. The same relationships were found in sites in the UK where there has been a significant reduction in Al_i concentrations. Hydrology (discharge) and temperature (daily deviation from norm) were not found to have any significant explanatory value in the Norwegian high order water courses at a long term scale.

25 Organizer of the workshop:

The main organizer of this workshop is the research school “Biogeochemistry in a changing environment” coordinated by Professor Jan Mulder, IPM, IMB. The research school has been funded by the Norwegian University of Life Sciences.

In addition to IPM, UMB, the workshop has been co-organized by the partners of the research school. The partners include research groups at UMB’s Department of Ecology & Natural Resource Management, the University of Oslo (Departments of Geosciences, Biology and Chemistry) and three independent national research institutes (Norwegian Institute for Water Research (NIVA), Norwegian Institute for Agricultural and Environmental Research (Bioforsk) and Norwegian Forest and Landscape Institute).