The Effects of Specific Root Length on Soil Decomposition Processes and Carbon Respiration
Marie-Anne de Graaff
Soils store more carbon (C) than vegetation and the atmosphere combined, thus small changes in the amount of C stored in soil can alter atmospheric CO2 concentrations. Since CO2 is a greenhouse gas, it is important that we understand the biological processes that drive soil C storage for accurate predictions of future global temperatures. Soil C storage is a function of the balance between soil C input via plants and soil C output via microbial decomposition. Plant roots contribute to regulating both processes, making them an important component of the global C cycle. Plant root turnover is a major contributor to soil organic carbon (SOC) input, which regulates soil microbial activity and thus the rate of C cycles among plants, soils and the atmosphere. The majority of root-C input to soil is derived from the finest roots in a system, but it is currently uncertain how specific root length (i.e. the relative abundance of fine versus coarse roots) affects decomposition processes and thus loss of soil C to the atmosphere. The objective of this experiment is to determine if and how differences in specific root length (cm/g) affect decomposition processes in soil. We predicted that increased surface area from fibrous root systems increases decomposition rates in soil due to enhanced root derived C inputs. To determine how root architecture affects decomposition and C respiration, we collected soil from six different switchgrass cultivars grown at Argonne National Lab in Illinois. The samples were collected at different depths (0-60cm), and then incubated for 60 days. The roots were extracted and analyzed using WinRhizo (Regent Instruments Inc., Quebec, Canada) for fine (0-.5mm), medium (0.5-1mm) and coarse (1-2.5mm) architecture. Following analysis, root samples were dried and weighed. We found significant differences in root architecture among switchgrass cultivars and are currently evaluating how those differences affect decomposition processes.