AT THE ROOT OF SUSTAINABLE BIOENERGY: USING GENETIC VARIATION IN ROOT TRAITS TO MAXIMIZE SOIL CARBON SEQUESTRATION AND BIOMASS YIELDS

Land use change for bioenergy production can create substantial green house gas (GHG) emissions through removal of standing vegetation and disturbance of soil carbon (C) pools. A recent body of literature suggests that native species with extensive root systems can rapidly repay the GHG debt, particularly when grown in diverse mixtures, by enhancing biomass production and soil C sequestration upon land-use change. Native bioenergy candidate species, switchgrass (Panicum virgatum L.), also show extensive within-species variation, and our group has collected novel preliminary data showing that increased cultivar diversity can enhance aboveground biomass production. With this proposed project we wish to assess: (1) whether shifting C3-dominated nonnative perennial grasslands to C4-dominated native perennial grasslands repay the C debt of land-use change by increasing soil C sequestration within the early years of establishment; (2) whether increased variation in root traits in species and cultivar mixes of native perennial grasses will enhance biomass production, soil C storage and the efficiency of nitrogen (N) cycling (i.e., decrease N losses); and (3) whether energy gain resulting from an increase in soil C storage and yield, along with a decrease in nutrient inputs and losses in low-input diverse mixtures of perennial grasses, is sufficient to offset energy gain from relatively greater biomass production in high input monocultures of perennial grasses. We will leverage an ongoing experiment conducted at the Fermilab National Environmental Research Park that compares different approaches for perennial feedstock production ranging across a biodiversity gradient, where diversity is manipulated at both the species- and cultivar level, and N is applied at two levels (0 and 67 kg/ha). Ultimately the goal of our proposed project is to evaluate which method of land-use change for bioenergy production maximizes yields, while minimizing the negative impacts of land-use change on the environment. This project will be the first to assess how within-species biodiversity can be used to maximize yields while minimizing inputs to the system, thereby reducing negative impacts of bioenergy feedstock production on the environment. Outcomes of our project can inform resource managers about the potential of a new approach for improving the sustainability of bioenergy feedstock production in the long-term by simultaneously (1) reducing the amount of nutrients needed to produce bioenergy feedstocks and (2) promoting soil quality through enhancement of soil C sequestration. In addition, this approach to bioenergy production will take better advantage of existing germplasm to maximize yields and C sequestration.