Extensive cultivation has degraded and destroyed most of the tallgrass prairie ecosystem. In recent decades, re-introduction of native grasses has become common practice to improve soil and water quality. We investigated changes in soil microbial phospholipid fatty acid (PLFA) profiles during grassland restoration using two chronosequences (15 sites on silty clay loam soil and 21 sites on fine loamy sand soil) of fields seeded to native C4 grasses through the Conservation Reserve Program (CRP) in Nebraska. Restoration age ranged from 8-18 and 2-19 years in the silty clay loam and loamy sand chronosequences, respectively. We also compared soil microbial communities in restored grasslands to native prairie and continuously cultivated systems, representative of target and time zero (unrestored) conditions, respectively. Composite samples of twenty 2-cm dia. soil cores separated into 0-10 and 10-20 depths were collected from each field in May of 2007. PLFAs were extracted from samples using a chloroform:phosphate buffer procedure.
Results/Conclusions
Total PLFA biomass and richness (total number of PLFAs detected) was higher on silty clay loam soils than fine loamy sand (P<0.001). Total PLFA biomass and richness increased with time since restoration (P<0.001 and P=0.002, respectively) in 0-10 cm when all sites were considered, regardless of soil texture. Similarly, fungal biomarkers increased with time in both the 0-10 cm (P=0.001) and 10-20 cm (P<0.001) depth increments when all sites were considered. Collectively, the restored sites exhibited PLFA biomass, fungal biomarkers, and richness intermediate of continuously cultivated and native prairie soil. In summary, the re-introduction of native C4 grasses in long-term cultivated systems promoted PLFA richness and biomass (total and fungal) over time, but these aspects of soil microbial community structure did not represent native prairie within 20 years of restoration. Furthermore, soil texture may affect the rate at which soil microbial communities recover, which may have consequences for recovery rates of soil carbon and nitrogen pools and long-term sustainability of restored soils.
