The proposed research investigates the impact of plant chemical inputs on soil microbial processes in the Alaskan taiga forest. Studies will focus on tannins produced by alder and balsam poplar, two species that form part of the successional sequence in the floodplain forests of Alaska. Tannins of varying chemical structure will be isolated from these species and added to soils from both alder and poplar sites. Their effects on a suite of microbial processes including respiration, nitrogen mineralization, and enzyme activities will be measured. The specific structure of the chemicals will be linked with their biological activities to improve our understanding of the ecological function of these chemicals. Tannins will be applied from each species to each soil to determine whether the microbial communities can adapt to the chemicals coming in. These studies will greatly improve our understanding of how plants affect the soil processes that control nutrient availability and therefore plant succession in the Alaskan taiga. We will improve our understanding of forest community dynamics, controls on litter quality and decomposition, plant-microbe interactions, and the role of microbial community composition in ecosystem function.
