Variation in carbon sequestration in response to water limitation in a diverse panel of switchgrass genotypes

Switchgrass (Panicum virgatum L.) has been identified as a "model" herbaceous species for bioenergy production by the United States Department of Energy. Switchgrass can provide several ecosystem services, including biodiversity support, soil erosion control, runoff filtering, and reclamation of marginal land. In addition to the reduction in greenhouse gas emissions from switchgrass-derived biofuel, soil carbon sequestration is of particular importance. The objective of this study was to evaluate the variability in soil carbon sequestration, particularly in response to water limitation, and to investigate the relationship between soil carbon sequestration and switchgrass yield. For this purpose, dry aboveground biomass yield and soil reactive carbon-specifically, permanganate oxidizable carbon (POXC)-content at three depths (0-15, 15-30, and 30-60 cm) were measured for 150 different switchgrass genotypes for three consecutive years. We found that drought significantly reduced yield compared to control plots, reduced the amount of soil POXC, and that POXC decreased with soil depth. A positive correlation (r = 0.27, p < 0.05) between POXC and yield was observed in the drought-stressed plots. This study provides insight into the impact of switchgrass on soil POXC over time and at different depths, offering a framework for future evaluation of root-related traits in switchgrass, particularly in relation to drought stress.