The overall goal of the Hubbard Brook LTER project is a better understanding of the response of northern hardwood-conifer watersheds to large-scale disturbance. We continue to approach this goal through a coordinated program of long-term monitoring, whole-watershed manipulations smaller scale experiments and surveys, and development of simulation models. Drawing upon continuous, long-term monitoring of the quantity and chemistry of precipitation and streamflow, as well as periodic measurement of forest composition biomass and chemistry for several watersheds with contrasting disturbance histories we are quantifying changes in ecosytem structure and function over the time scale of several decades in a northern hardwood-conifer forest.
Increasingly the Hubbard Brook program is seeking mechanistic explanations for the behavior of biogeochemical cycles in ecosystems. Integration of biogeochemical studies and assessments of ecosystem response to disturbance have long been hindered by difficulties in analyzing element-element interactions. Because virtually every pathway of element transfer is coupled to the H-ion cycle, proton budgets serve to couple element cycles through the stoichiometry of biogeochemlcai reactions. Thus, we are focusing our efforts on the development of proton budgets for contrasting watersheds in the Hubbard Brook Valley, utilizing process studies to quantify pathways and the small watershed approach coupled with intensive soil measurements to verify the internal proton budgets. Our detailed program of process studies on reference and treated watersheds includes:
- Analysis of vegetation development using permanent plots, natural and experimental gaps, quantification of neighborhood competition, and ecophysiology and life history studies of dominant species
- Organic matter processing in soils and streams, long-term decay of bole wood, and the formation and disruption of organic debris dams
- Biogeochemical processes such as wet and dry deposition stream channelization and outflow, and soil solution chemistry and weathering
- Hillslope hydrology and routing of rain and snowmelt to streams using field manipulations and monitoring as well as hydrologic models
The Hubbard Brook LTER program also concentrates on the dynamics of certain critical heterotroph populations in northern hardwood-conifer ecosystems. Building upon long-term records of breeding bird populations in the area, we are seeking mechanistic explanations of fluctuations in population sizes of birds and phytophagous insects. We are investigating the complexities and controls of food webs in first- and second-order mountain streams, focusing especially on bacterial productivity. Finally, we are examining the controls on populations of an important pathogenic fungus and the nutritional ecology of a large herbivore – the white-tailed deer.
Major participants:
- Timothy Fahey, Cornell University
- Charles Driscoll, Syracuse University
- F. Herbert Bormann, Yale University
- Breck Bowden, University of New Hampshire
- Jon Cole, Institute of Ecosystem Studies
- John Eaton, Institute of Ecosystem Studies
- C. Anthony Federer, U.S. Forest Service
- Stuart Findiay, Institute of Ecosystem Studies
- Richard Holmes, Dartmouth College
- Jeffrey Hughes, Cornell University
- Arthur Johnson, University of Pennsylvania
- Gene Likens, Institute of Ecosystem Studies
- Gary Lovett, Institute of Ecosystem Studies
- David Pearl, Dartmouth College
- Robert Pierce, U.S. Forest Service
- William Reiners, University of Wyoming
- Tom Siccama, Yale University
- William Smith, Yale University
- Louise Tritton, U.S. Forest Service
For additional information contact Tim Fahey, Department of Natural Resources, Cornell University Ithaca, NY 14853.
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