Switchgrass Ecotype Contributions to Soil Organic Carbon, Deep Soil Microbial Community Composition and Rhizodeposit Uptake.

Perennial cellulosic bioenergy crops such as switchgrass (Panicum virgatum L.) can improve marginally productive cropland and sequester C throughout the soil profile. Switchgrass ecotypes vary in their belowground plant allocation and rooting characteristics which could impact soil C cycling and rhizodeposit contributions to microbial community abundance and composition. We report the results of a 1 year field experiment following plant uptake, root biomass, and rhizodeposit uptake after a  pulse-chase ¹³C labeling experiment of two switchgrass cultivars, Kanlow and Summer. Active microbial community composition and rhizodeposit C uptake were different between the two cultivars, and reflected differences in root structure. The microbial community associated with the thinner roots of Summer had rhizodeposit C uptake associated primarily with saprotrophic fungi. Rhizodeposit C from Kanlow’s thicker roots was processed primarily by G- bacteria. These results suggest that plant-specific interactions with the microbial community can induce a variety of C sequestration mechanisms.