OOS 21-9
Root controls on soil organic carbon dynamics

Wednesday, August 13, 2014: 10:50 AM
203, Sacramento Convention Center
Marie-Anne de Graaff, Department of Biological Sciences, Boise State University, Boise, ID

Root derived soil carbon (C) inputs, the soil microbial community, and the soil C cycle are intrinsically linked, because roots supply soil microbes with highly assimilable C-rich substrates that drive microbial decomposition processes. Environmental perturbations, such as land use change, climate change or increasing atmospheric CO2 concentrations can alter the relative allocation of C to belowground organs in plants, which can change root-derived soil C input, and the availability of C to soil microbes. Importantly, root-derived C inputs can stimulate decomposition of more recalcitrant soil organic carbon (SOC) by priming microbial activity which can lead to a net loss in soil C storage. Despite a general consensus that root-derived C inputs are a key component of the soil C cycle, the effect of changes in root-derived C release on soil C cycling remains highly uncertain. With a series of field and laboratory experiments that manipulate root C inputs to soils under a variety of environmental conditions, we explore how root derived C inputs and changes therein affect soil C dynamics. Labeling plants, plant litter or root exudates with 13C has allowed us to evaluate the cycling of root C, as well as determine how changes in root C inputs affect the cycling of SOC.


We found that changes in climate can affect root morphology and that root morphology influences the quantity and the fate of root-derived soil C inputs. Changes in root-C inputs to soil significantly affect SOC decomposition, and the magnitude of this effect appears to be largely driven by the amount of available soil C relative to the change in quantity of root-derived soil C input. We suggest climate induced changes in root C inputs, as well as potential changes in available soil C across the profile that can alter the ratio of soil C availability relative to root-C input over-time, should to be taken into account when modeling impacts of climate change on SOC cycling.