Fire is a major controller of carbon (C) cycling in terrestrial ecosystems, by converting plant biomass to atmospheric CO2 and by contributing incompletely combusted biomass or "black carbon" (BC) to soils. The scientific understanding of the short- and long-term fates of BC in terrestrial ecosystems is incomplete, and a critical knowledge gap exists in our understanding of the fate of BC in the environment. BC, may significantly affect soil C stocks and rates of CO2 exchange of forests with the atmosphere. Through integrated field and laboratory studies, this research will improve understanding of fundamental biological, chemical and physical controls on BC degradation and transport processes in a northern forest soil. This research will link the charring temperature of BC materials to their chemical and physical structures and their resulting decay rates, activity of the main decomposers, enzyme activities, transport dynamics, and stabilization mechanisms in soil. The proposed experimental approach will use stable isotope-enriched (13C and 15N) BC materials produced over a range of temperatures (200 to 600ºC) and its precursor wood of jack pine, a fire-prone and abundant tree species in eastern North America, to elucidate the structures of BC materials and track the multiple fates of these materials when added to soil. This approach will permit a direct assessment of the biological turnover in soil using advanced molecular and spectroscopic techniques. This work will provide the first look at the roles of specific groups of microorganisms and soil fauna involved in the decomposition and movement of BC and wood in soils. To test the effects of plant species on BC chemical and physical structures, highly 13C- and 15N-enriched BC from red maple will be compared with the jack pine. Resulting data and knowledge will contribute to ongoing efforts to predict terrestrial C cycling, and will inform ecosystem and climate modelers and also land use managers.
Most existing climate models predict that temperate and boreal forests will experience greater fire frequency under a warmer future climate, thereby increasing BC (black carbon) contributions to soils. In addition, substantial BC (or "biochar") production is expected from the energy industry. This research will characterize the key biological, chemical and physical controls on BC and wood degradation processes in soils, thereby substantially increasing our understanding of the mechanisms involved in C stabilization and sequestration in fire-prone forests. This will provide information needed to improve ecosystem and global C cycling models and their uses in characterizing forest soil C sinks in present and future climates. This research will inform a broad scientific, educational, land manager and agency community interested in ecosystem function, productivity and sustainability. In addition, the project will include involvement of a science teacher from a New York City minority-serving high school and the NY GLOBE Metro program to integrate applied environmental ecosystem science and geosciences into the high school biology and earth science curricula. Purdue University, in collaboration with Leech Lake Tribal College (LLTC), will integrate this research into an ethnobiology curriculum focusing on both modern principles of chemistry and Native American utilization of BC. The University of Michigan Biological Station and City University of New York will each train a postdoctoral researcher within the scope of this project and will use the field study as a resource for on-site university courses, its site-based undergraduate and graduate student research programs, and its science outreach.
