| Land-use influences microbial community composition and carbon (C) and nitrogen (N) dynamics. Land-use includes a suite of cultural practices, vegetation, and associated soil characteristics. Effects of land-use history, plants, soil rewetting and resource availability, and seasonality on microbial community composition were investigated along a gradient of increasing intensity of soil disturbance with similar soil type in the Central Coast of California. Land-uses included relict native perennial grasslands, old-field annual grasslands, hayfields, restored perennial grasslands, row-cropped perennial bunchgrasses for seed production, and vegetable fields.; Microbial communities were found to vary by land-use history based on phospholipid fatty acid (PLFA) analysis. The greatest distinction occurred between grassland and cultivated soils. Among grassland soils, microbial communities of annual, restored perennial and relict perennial grasslands were distinct from each other. Gradients in labile soil C and soil moisture distinguished microbial communities of grassland soils from each other, while soil pH and management inputs like fertilizer, pesticides, and herbicides distinguished microbial communities in cultivated soils vs. grassland soils.; Rainfall in Mediterranean climates may affect soil microbial processes and communities differently in agricultural vs. grassland soils, in which C and N availability (i.e., resource richness) differs by land-use history. Grasslands had higher C and N pools than cultivated sites. Trace N gases and carbon dioxide efflux increased, but soil C and N pools did not respond to a mild wet-dry cycle. Rewetting preferentially increased the activity of a resource-rich grassland soil, but less temporal change in microbial community composition and physiological status occurred in more resource-poor grassland and cultivated soils.; Effects of plant presence and seasonality on microbial communities, activity, and soil resources were investigated in land-uses supporting native perennial bunchgrasses, Nassella pulchra. Microbial communities differentiated by season within a given site. Soils with plants supported microbial communities distinct from bare soils in winter and/or spring. The PLFA that distinguished plant from bare soils varied by site, suggesting that land-use history and associated environmental conditions influenced microbial communities. Changes in communities corresponded to increases in microbial respiration and net mineralizable N, indicating possible links between community composition and function. |
