Plant species composition, soil biology, and carbon storage in grasslands

摘要: The primary focus of this project was on plants with different rooting attributes, effects of roots on microbial communities, and contribution of root-related processes to soil C retention, but fates of aboveground litter were also examined. In a project comparing deep soil profiles, there were very few differences between annual grassland and restored perennial grassland in their total soil C, soil microbial C, CO2 efflux from soil, soil CO2 concentrations in the soil atmosphere, and soil microbial community composition based on phospholipid fatty acid (PLFA) profiles, although root length of the native perennials were slightly lower at the surface and greater at lower depths than in the annual grass-dominated areas. The two years of tillage to reduce non-native annuals prior to planting perennials thus did not have a long-lasting effect on soil C pools, compared to the annual grassland starting point. Long-term tillage for six years with no plants present, however, resulted in much lower C pools, lower decomposition of litter in litterbags, and changes in microbial community composition, eg, absence of a PLFA fungal biomarker. Root effects also tended to be minor in another project that compared “bare” treatments (plants were removed) vs.“plant” treatments (the perennial bunchgrass, Nassella pulchra, was present), although some sites such as relict perennial grassland showed higher C pools and different PLFA in the “plant” treatment. In contrast, other related projects showed that aboveground litter deposition had pronounced effects on the soil surface layer, including microbial biomass, activity, and community composition. Addition of C4 litter resulted in …