A Changing Arctic: Ecological Consequences for Tundra, Streams and Lakes
Total Page：16
File Type：pdf, Size：1020Kb
A CHANGING ARCTIC: ECOLOGICAL CONSEQUENCES FOR TUNDRA, STREAMS AND LAKES Edited by John E. Hobbie George W. Kling Chapter 1. Introduction Chapter 2. Climate and Hydrometeorology of the Toolik Lake Region and the Kuparuk River Basin: Past, Present, and Future Chapter 3. Glacial History and Long-Term Ecology of the Toolik Lake Region Chapter 4. Late-Quaternary Environmental and Ecological History of the Arctic Foothills, Northern Alaska Chapter 5. Terrestrial Ecosystems Chapter 6. Land-Water Interactions Research Chapter 7. Ecology of Streams of the Toolik Region Chapter 8. The Response of Arctic-LTER Lakes to Environmental Change Chapter 9. Mercury in the Alaskan Arctic Chapter 10. Ecological consequences of present and future change 1 <1>Chapter 1. Introduction John E. Hobbie <1>Description of the Arctic LTER site and project Toolik, the field site of the Arctic Long Term Ecological Research (LTER) project, lies 170 km south of Prudhoe Bay in the foothills of Alaska’s North Slope near the Toolik Field Station (TFS) of the University of Alaska Fairbanks (Fig. 1.1).[INSERT FIGURE 1.1 HERE] The project goal is to describe the communities of organisms and their ecology, to measure changes that are occurring, and to predict the ecology of this region in the next century. Research at the Toolik Lake site began in the summer of 1975 when the completion of the gravel road alongside the Trans-Alaska Pipeline, now called the Dalton Highway, opened the road-less North Slope for research. This book synthesizes the research results from this site since 1975, as supported by various government agencies but mainly by the U.S. National Science Foundation (NSF), and focuses on the Arctic LTER project started in 1987. Toolik Lake is located in the foothills of the North Slope (Fig. 1.1), the arctic region of northern Alaska, at 68o38’N and 149o43’W and an altitude of 719 m. The LTER research site is defined as the catchment south of the junction of two rivers: the Toolik Lake outlet and the headwaters of the Kuparuk River (Fig. 1.2).[INSERT FIGURE 1.2 HERE] The view looking south from above Toolik Lake shows the Toolik Field Station, the inlet stream, numerous lakes in the inlet basin, and the Brooks Range (Fig. 1.3).[INSERT FIGURE 1.3 HERE] 2 The North Slope (about the size of Nebraska) encompasses the 207,000 km2 of Alaska that drain to the Arctic Ocean. There are three physiographic divisions: coastal plain (71,000 km2), foothills (62,400 km2), and mountains (73,600 km2). The North Slope is underlain by hundreds of meters of permafrost, which is defined as earth material (soil, rock, ice, and organic matter) that remains at or below 0 °C for at least two consecutive years (van Everdingen 1988). Permafrost is a product of the low annual temperature of -8 oC at Toolik; it limits the plants and roots to the upper layer of soil, called the active layer, which thaws during the three months of summer. Permafrost also holds the ~300 mm of annual precipitation at the surface so the tundra is moist, rivers and streams plentiful, and wetlands, ponds, and lakes abundant. The largest disturbance affecting this site occurred when a series of glaciers advanced northward from the valleys of the Brooks Range during the last ice age. Today, the age of the land surface across the research site is either >300,000 years, ~60,000 years, or ~10,000 years (Chapter 3). The age affects the chemistry and topography with the result that there are characteristic drainage patterns, land forms, and even vegetation communities on each of these glacial tills. The dominant plants of the foothills are the sedges and grasses of tussock tundra, a vegetation type that covers some 80 % of arctic Alaska. Low shrubs, including birches and willows, grow between the tussocks and abundantly along the streams. Nutrients, particularly nitrogen (N), are in short supply and primary productivity low. Low concentrations of N and phosphorus (P) are also found in streams and lakes; both are ultra-oligotrophic. During the nine months of winter the lakes are covered with ~1.5 m of ice and the streams are frozen solid. <2>Advantages of the Site for LTER Research 3 The LTER program includes more than 20 sites located in most of the major biomes of the U.S., surrounding oceans, and of the Polar Regions. In the north, there is the boreal Bonanza Creek site near Fairbanks, Alaska, and the Arctic LTER site at Toolik Lake. For comparative studies of ecological questions in the LTER network, the Toolik site provides the cold end of a temperature gradient and also a virtually pristine site where natural communities of fish and wildlife continue to exist and there is little air-borne pollution. There is virtually no nitrogen deposition from acid rain and the western Arctic location of the site minimizes the cross-pole deposition of pollutants (Ford et al. 1995). This contrasts with the Canadian Arctic where deposition of pollutants from Europe can be high. The site has become the location for a large number of non-LTER research projects, many of which cooperate with the LTER. It is quite probably the best known arctic research site because of logistics that include an excellent living and research facility, helicopter and truck transportation, the availability of the LTER database containing all the data since 1975, and availability of climate information from the LTER and the TFS. The LTER data set provides researchers with climate data, soil chemistry information, vegetation distribution information, the results of experiments, and other ecological information from many projects. In addition, scientists make use of the long-term terrestrial experiments (some running for more than 20 years) of warming the tundra, fertilizing the tundra and streams, reducing the available solar radiation to plants, and excluding grazing animals. <1>History of Research at the Toolik LTER site 4 <2>Research on the Coastal Plain: Naval Arctic Research Laboratory (NARL) Environmental research on the North Slope of Alaska, summarized by Hobbie (1997) and Shaver (1996), began during the 1882 First International Polar Year when a research station was set up at Barrow. Over the next 60 years, expeditions collected plants and animals and surveyed the geological features. “Big science” in the north began in 1947 when the Arctic Research Laboratory, the predecessor of NARL, was established at the edge of the coastal plain at Barrow. The Office of Naval Research (ONR) at that time operated as a source of federal money for basic research at university laboratories (summarized from England 1982). Over the next three decades, NARL-ONR-supported research covered every aspect of the arctic environment including soils, vegetation, permafrost, beach formation, microbiology, taxonomy, marine biology, limnology, and atmospheric concentrations of carbon dioxide. The enlightened attitude of ONR was stated by Britton (1973, p. 11) that to the Navy "fell a first responsibility, and what might be considered a moral commitment, to learn both how to use the environment and how to protect it." Not only was research carried out near Barrow, but also float planes were used to set up field camps in the mountains on deep lakes in the Brooks Range (Livingstone et al. 1958, Hobbie 1964). “Big international science” reached the North Slope in the three years (1971-1973) of the NSF-funded International Biological Programme (IBP) at Barrow. The overall themes were (1) to develop a predictive understanding of the arctic ecosystem, (2) to obtain a database for modeling and comparison, and (3) to use environmental knowledge for problems of degradation, maintenance, and restoration of ecosystems. All of the major ecosystem components such as primary producers, decomposers, herbivores, predators, climate and microclimate, and soils, 5 were studied on the same site. For the aquatic study, investigators focused on three small ponds (results synthesized in Hobbie 1980). In the terrestrial study, the focus site was the wet sedge tundra (reported in Brown et al. 1980). One of the ways the entire project was integrated was the whole-system goal of understanding carbon, nitrogen, and phosphorus cycling. The scale of support and facilities enabled scientists to go far beyond descriptive ecology and investigate the processes and controls of carbon and nutrient fluxes. And the scale of support was immense; there were hundreds of scientists at Barrow during the IBP, 32 authors for the terrestrial book, and 19 for the aquatic study. In many ways, some of the IBP goals were ahead of the available technology. Computer programs for a database had to be written de novo, took years to complete, and never worked well. Ecological modeling of large systems was just beginning and computers were small; model results were inconclusive although the aquatic program pioneered the development of stochastic versions of deterministic models (e.g., Tiwari et al. 1978). However, the processes necessary for the modeling were studied in well-documented detail, many for the first time in the Arctic. The relationships and parameters from the IBP studies are still used in ecological modeling today (e.g., the effects of temperature and moisture on decomposition determined by Flanagan and Veum (1974)). The integration of research caused by the modeling efforts, by the concentration of research onto a single site, and by the crush of scientists and students into the close living and laboratory quarters at NARL produced close interactions and sharing of information. <2>Research in the Foothills: Toolik Lake, R4D, LTER 6 At the end of the IBP project in 1974, the aquatic scientists decided to look for a new site on the North Slope where they could investigate deeper lakes in the foothills, an area never before studied in arctic Alaska.