The greatest uncertainty of carbon budgets in forest ecosystems appears to be in the magnitude and factors controlling partitioning of carbon to above- versus belowground production. Dr. Gower, Running, and Gholz propose to measure key carbon budget indices at four forests of widely contrasting climate (each with control and fertilized stands). Their analyses will concentrate on relative carbon budgets of the contrasting sites, produced by identical measurements, rather than a detailed carbon budget on one site. They will estimate above- and belowground net primary production and indices of canopy photosynthetic production and stem, branch, and root respiration losses of conifer forests in Oregon, Montana, Wisconsin and Florida. An established ecosystem process model that calculates water, carbon and nitrogen cycles in forests will be used to integrate field data, interpolate between measurement periods and evaluate their hypotheses on variable carbon partitioning patterns in diverse climates. Detailed data from an on-going intensive study at the Florida site will be used to place their relative budgets into context. Results should provide improved fundamental understanding of environmental controls on forest productivity, allowing better projections of forest responses to perturbations such as air pollution and climate change.
