Susan E. Trumbore

I study the role of terrestrial ecosystems in the Earth's global carbon cycle, with emphasis on quanitfying the magnitude and timing of their responses to land use and climate change. This research addresses basic questions about how ecosystems function and applied questions about the role they will play in the carbon cycle of the next century. As an isotope geochemist, my major contribution has been to use radiocarbon (14C) to infer the timescales of C exchange between the atmosphere, plants and soil organic matter. My collaborators and I have used cosmogenically produced 14C to determine the age of slow-growing trees that lack annual growth rings and to demonstrate a quantitative link between soil minerals and the age of stored soil carbon. We trace the "bomb" 14C released to the atmosphere in the 1960s by atmospheric thermonuclear weapons testing through terrestrial C reservoirs to quantify the dynamics of C on decadal timescales. Comparison of the rates of turnover in the context of soil forming factors are helping to unravel the short- and long-term controls on ecosystem C storage and dynamics. Recently, we have used radiocarbon to partition sources of C lost from ecosystems as respiration or DOC by age, and to test hypotheses about the mechanisms for rapid destabilization of older organic matter stored in soil.