Title: Regionalizing the Harvard Forest Long-Term Flux Measurements: Complementary Studies From Howland, Maine Principal Investigator: Stewart M. Goltz, Department of Applied Ecology and Environmental Sciences, University of Maine Co-investigator: David Y. Hollinger, NE Experiment Station, USDA Forest Service Co-investigator: Eric Davidson, Woods Hole Research Center Project Summary We propose to carry out long-term eddy correlation flux measurements of CO2, sensible heat, latent heat, and momentum in the Howland forest in central Maine. We will monitor abiotic (air and soil temperatures, light, soil moisture, etc.) and biotic factors (timing of needle expansion, cambial growth, etc.) to achieve our goal of understanding the mechanisms responsible for regulating forest carbon exchange and storage. These studies will directly complement similar, on-going work at the Harvard forest in two ways. First, the Howland site is dominated by evergreen species in contrast to the deciduous hardwoods at the Harvard forest, allowing us to test hypotheses relating to the impact of plant growth-form and environment on ecosystem CO2 exchange. Secondly, we will exploit correlated regional deviations in the monthly climatic parameters of temperature, rainfall, and cloudiness between the two sites to test several hypotheses relating to the environmental regulation of net ecosystem CO2 exchange and forest carbon storage. In this way we can increase the power of the natural experiments with which we must work. We will maintain a close liaison with the Harvard Forest flux measurement group during all phases of this work.   Project Duration: July 1, 1995--June 30, 1998 Funding Agency: National Institute for Global Environmental Change (NIGEC) Title: Patch And Regional Scale Studies Of Forest Carbon Exchange Principal Investigator: David Y. Hollinger, NE Experiment Station, USDA Forest Service Co-investigator: Todd Dawson, Section of Ecology and Systematics, Cornell University Co-investigator: Stewart M. Goltz, Department of Applied Ecology and Environmental Sciences, University of Maine Co-investigator: Eric Davidson, Woods Hole Research Center Co-investigator: Harry T. Valentine, NE Experiment Station, USDA Forest Service Project Summary We propose to carry out long-term eddy correlation flux measurements of CO2, sensible heat, latent heat, and momentum in and above a boreal forest near Howland, in central Maine. To achieve our goal of understanding the mechanisms responsible for regulating forest carbon exchange and storage, fluxes will be related to abiotic (air and soil temperatures, light, soil moisture, etc.) and biotic factors (timing of needle expansion, cambial growth, insect damage, etc.). We will experimentally determine parameter values for simple, mechanistic models of above- and belowground processes, and will use these models to guide our investigations and to interpret results. These studies of forest patch-level fluxes will be complemented by regional measurements of CO2 exchange to determine the degree to which flux estimates and a mechanistic understanding derived at the patch scale (~1 - 5 ha) are applicable to the regional scale (10's of km2). Regional flux measurements will be made from a light aircraft utilizing the convective boundary layer (CBL) budget approach and also compared with estimates generated by combining modeled CBL height development with tower based measurements of CO2 concentration to test the utility of using archived data to retrospectively estimate regional CO2 fluxes. Studies of stable isotope discrimination of deuterium and 18O in water and 13C and 18O in CO2 in ecosystem pools and fluxes will assist in the mechanistic interpretation of ecosystem and regional carbon exchange. Through its focus on understanding the interactions that control the exchange of CO2 between a terrestrial ecosystem and the atmosphere, quantifying carbon sources and sinks, and providing process-based information on biogeochemical cycling, the proposed studies directly address research area (1) of the joint program on terrestrial ecology and global change. These studies are also relevant to area (3) of the joint program which relates to how ecological properties influence other feedbacks on the climate system. Project Duration: October 1, 1995--September 30, 1998 Funding Agency: NSF Interagency Terrestrial Ecology and Global Change Program