Evaluating plant-soil-microbial interactions in low-input high-diversity biofuels: Enhancing aboveground ecosystem services while increasing carbon sequestration

Background/Question/Methods

Low-input high-diversity (LIHD) cultivation includes multiple native grass and forb species that may provide sustainable, low-input biofuel feedstock. Research on restored prairies indicates LIHD sites can produce greater long-term yields than monocultures.  Diverse grassland plantings provide multiple benefits such as habitat for invertebrates and wildlife. Low-input cultivation reduces fertilizer input and nutrient leaching, while increasing arbuscular mycorrhizal (AM) fungi, potentially leading to improved soil health and carbon sequestration. Our study assessed mycorrhizal hyphal abundance and soil quality under LIHD cultivation in established plots at Argonne National Laboratory, Illinois. We compared intra-specific diversity with three different switchgrass cultivars and inter-specific diversity with combinations of switchgrass and other native prairie grasses and forb species. Annual productivity of extra-radical AM hyphae was assessed using hyphal in-growth bags, inter-radical colonization was determined using microscopic assessment. Phospholipid and neutral-lipid fatty acid analyses were used to determine soil microbial community composition and AM fungal biomass. Aboveground productivity for each plant species was assessed at harvest. The major goal of this project is to develop LIHD cultivation that will produce high biomass without increased nutrient inputs, which will ultimately sustain wildlife habitat and increase carbon sequestration.   

Results/Conclusions

Our field data indicates both inter-specific and intra-specific plant species biodiversity produced equal or greater aboveground biomass compared to monocultures of switchgrass, and multiple genotypes of switchgrass had greater annual production of arbuscular mycorrhizal fungi, compared to the switchgrass monocultures. A positive correlation between AM hyphal abundance and soil aggregation and carbon sequestration was observed.  Previous studies have shown that invertebrate species richness is positively correlated with plant species richness, and floral species richness and abundance led to greater bee abundance and bee species richness.  Therefore, we predict that higher inter- and intra-specific plant species diversity will support greater invertebrate abundance and diversity, and these assessments are currently in progress.  Results of our study will inform plant breeders on feedstock management that will decrease fertilizer inputs, improve aboveground ecosystem services, such as wildlife habitat, while also increasing belowgound services such as soil health and soil carbon sequestration, all without a loss in production.