A Radiocarbon Database for Improving Understanding of Global Soil Carbon Dynamics: Part I

Soils play a large role in the global carbon cycle, but soil carbon stocks and dynamics remain highly uncertain. Radiocarbon (14C) observations from soils and soil respiration provide one of the only ways to infer terrestrial carbon turnover times or to test ecosystem carbon models. Although a wealth of such observations exists, they are scattered in small data sets held by individual researchers, and have not been compiled in a form easy to use for multi-site analysis, global assessments, or model testing. Here we introduce a new, global radiocarbon database that will synthesize datasets from multiple contributors to facilitate research on three broad questions: (1) What are current patterns of soil carbon dynamics, and what factors influence these patterns? (2) What is the sequestration capacity of different soils? (3) What are likely impacts of global change on the soil resource? (4) How well do models represent important carbon cycle processes, and how can they be improved? In addition to assembling data in a common format for analyses, this database will offer query capabilities and the ability to combine data with gridded global products, such as temporally resolved temperature and precipitation, NPP and GPP, and a climate-based decomposition index. Some of the near-term synthesis goals include analyzing depth profiles of 14C for across gradients in ecosystem state factors (climate, organisms, relief, parent material, time, and human influence) and soil orders; mapping surface-soil 14C values on soil temperature and moisture; and comparing soil carbon turnover times to NPP and soil carbon stocks. We are currently incorporating data from 18 contributors and six continents, with 14C measurements from soils representing nine soil orders, plant and microbial tissues, and respiration fluxes. Our intention is to grow the database and make it available to a wide community of scientists. For example, observations for different disturbance, experimental treatment, or land-use regimes are sought. This presentation will introduce modelers, other data users, and potential new data contributors to this valuable resource for evaluating terrestrial carbon dynamics and responses to global change.