Dynamics of soil microbial metabolic activity during grassland succession after farmland abandonment

Abstract

Secondary succession has a major influence on vegetation and soil biogeochemical processes, however, the dynamics of microbial metabolic activity and the driving factors during grassland succession after farmland abandonment remain unclear. Therefore, we examined variations in microbial biomass carbon (Cmic), soil basal respiration (BR), microbial quotient (Cmic:Corg), and metabolic quotient (qCO2) in sloping farmlands that had been abandoned for 0, 3, 8, 13, 18, 23 and 30 years on the Loess Plateau in China. Moreover, the plant, soil and microbial properties were determined to reveal the forces driving soil microbial metabolic activity. The results showed that compared to those of farmland, the Cmic significantly increased by 104.7% and 168.0%, while the qCO2 significantly decreased by 54.3% and 70.5%, respectively, in the late succession stages (23 and 30 years). Long-term succession (30 years) significantly enhanced the Cmic:Corg by 51.4%. In contrast, except for a decrease at 8 years, the BR changed little during grassland succession following farmland abandonment. These changes in microbial metabolic activity indicators were associated with shifts in litter biomass, soil organic carbon, available nitrogen, and soil fungi. Litter biomass and fungi were strongly affected the changes in microbial metabolic activity. This study provided new information regarding the dynamics of microbial metabolic activity during long-term secondary succession and enhanced our understanding of the linkages among plant, soil and microorganisms in semiarid ecosystems.