PROCEEDINGS: Index of Abstracts

CLIMATIC AND POLLUTION INFLUENCES ON ECOSYSTEM PROCESSES IN NORTHERN HARDWOOD FORESTS

Kurt S. Pregitzer-1, David D. Reed-1, Glenn D. Mroz-1, Andrew J. Burton-1, John A. Witter-2, and Donald A. Zak-2

1-School of Forestry & Wood Products, Michigan Technological University, Houghton, MI 49931. 2-School of Natural Resources & Environment, University of Michigan, Ann Arbor, MI 48109.

The Michigan gradient study was established in 1987 to examine the effects of climate and atmospheric deposition on forest productivity and ecosystem processes in the Great Lakes region. Four intensively-monitored northern hardwood study sites are located along a climatic and pollutant gradient extending from southern lower Michigan to northwestern upper Michigan. The project continues today, with the following overall objectives: (1) to continue measuring key ecosystem variables at four sites; (2) to understand how carbon allocation, nutrient cycling, and forest productivity respond to differing levels of temperature, moisture availability, and atmospheric deposition; and (3) to quantify sources of temporal and spatial variability in ecosystem processes for use in regional modeling efforts. Additional research designed to investigate the effects of soil temperature and N availability on belowground processes was initiated at the sites in 1993. Objectives of this research are: (1) to quantify relationships between soil temperature and fine root longevity, and root system construction and maintenance costs; (2) to determine how soil nitrogen supply affects fine root construction and maintenance costs, and lifespan; (3) to understand the effects of soil temperature and nitrogen availability on soil respiration; and (4) to quantify the contributions of root and microbial respiration to respiratory flux from the soil.