INSTAAR Ecosystems Group

Ecosystems Group

The primary aim of the Ecosystems Group is to study the ecological components of arctic and alpine systems and their interactions with climatic and biophysical variables. The Ecosystems Group has recently expanded to include study of the tropics and human dimensions. Basic research topics include:

ecosystem dynamics
biogeochemical processes
biodiversity
ecosystem disturbance and recovery
modeling of biotic pattern distribution
ecological assessments
conservation planning

We address questions of how climatic influences, biophysical factors, and biotic components interact to control the distribution and maintenance of ecosystems; how the hierarchical organization of current ecosystems was produced in response to past and present environments; how predicted climatic changes and current and future changes in land-use patterns will affect ecosystems; and how conservation planning can contribute to sustainable ecosystems at multiple geographic scales. Ongoing projects investigate the following characteristics and scales of ecological systems: populations, species, communities, landscapes, and regions; plants and animals; biogeochemistry, ecophysiology, hydrology, patterns of biotic distribution, and biogeography; and above- and below-ground systems.

Background

Changes in ecosystem structure, function, and distribution, whether induced by global climatic shifts or by land use practices, have become a pressing and controversial topic worldwide. Public awareness and concern have increased in response to climatic events (e.g., droughts and blizzards) which have led to dramatic large-scale floods and fires. Indeed, such recent events as the Yellowstone fires and floods in the Midwest have led to the rapid implementation of regional ecological assessments in order to mitigate the effects of potential changes and sustain managed and natural ecosystems. The general public and politicians have increasingly sought answers from scientists about how much pressure ecosystems can withstand, what probable changes will occur, and how to sustain ecosystems within desirable bounds. As both public perception and need for scientific advice have increased, disagreements and lack of understanding have persisted concerning how the potential changes may affect ecosystems, whether and how human activities interact with other changes to alter ecosystems, and what the appropriate geographic and temporal scales are at which these changes may be expected.

To answer these questions, work in the Ecosystems Group is organized along six general scientific objectives:

effects of global changes on ecosystem composition and structure
degree to which various biogeochemical processes (e.g., C, N, and P cycles) constrain ecosystem response
relationships between biophysical and biotic components of ecosystems
determination of the appropriate ecological units for analysis at various geographic scales and definition of the types of ecological issues and functions that must be addressed at each scale
linkage of terrestrial and aquatic systems
prototyping new methods for conservation planning.

Recent Achievements

Hierarchical Ecological Classifications (HECs) are increasingly used in ecological assessments for management and conservation purposes at continental, regional and landscape scales. Decisions are made using these HECs that impact the economy and the human communities of entire regions.

Human-induced nitrogen deposition will have important influences on water quality and biotic communities in alpine environments. Replacement of slow growing dominant species with fast growing species can lead to a 10-fold increase in net N mineralization rates, higher soil NO3- levels, and potentially greater leaching of N into surface waters.

Rather than being recalcitrant organic material removed from energy and carbon cycling, humic substances partly control the degradation of organic contaminants found in marine and freshwater sediments. In research for the McMurdo Dry Valleys LTER project, progress was made on understanding nitrogen cycling in glacial meltwater streams that flow during the austral summer.

Autotrophic and heterotrophic organisms in alpine environments affect patterns of carbon and nitrogen sequestration in soils. Results have implications for policy dealing with carbon sequestration (e.g., several aspects of land use) and mitigation (e.g., power plants).

The conversion of tropical forests to cattle pasture in the central Amazon, Brazil, has both regional and global biogeochemical consequences. Loss of cations and phosphorous was correlated with soil types and management practices, and can be severe.

Water quality parameters can be utilized to understand ecosystem degradation in the context of the global-local continuum, and to translate science into public policy. New land-use codes serve as a model for how county, state, federal, and university researchers can work together to understand and protect natural resources.

The role of biotic factors (e.g. competition for resources, symbiotic N2-fixation, plant feedbacks to soil biogeochemistry) in determining the composition of species and spatial and temporal variation in ecosystem function in the alpine is critical. Understanding how changes in plant and microbial species influence the alpine is crucial to predicting the response of this system to environmental change.

Ecosystem nitrogen status measured in streamwaters. We propose that the ratio of the annual flux of DIN to DON in streamwaters provides a robust and sensitive method of determining the N-status of ecosystems from a variety of biomes.Our results from many biomes suggest that N-limited ecosystems have DIN:DON ratios less than 0.5 and that ecosystems where N is no longer limiting have DIN:DON ratios greater than 2.0. The DIN:DON ratio in annual riverine yields is independent of ecosystem N storage, rates of N cycling, magnitude of N yield in surface waters, and hence a robust indicator of the N-status of ecosystems.

Understanding amphibian population decline. Research on the global die-off of tropical amphibians has been linked to global-scale physical and biogeochemical processes. This work was integrated into the creation of a new network to monitor the amphibian die-off called RANA (Research and Analysis Network for Neotropical Amphibians), based in Costa Rica and founded in 2002.

See also:

For a snapshot of past activities, view the Ecosystems Group Description in the 1998 INSTAAR Annual Report (PDF file; 209 KB).
Kiowa Environmental Chemistry Laboratory
Terrestrial Ecosystem Analysis Laboratory (TEAL)