Changes in rhizosphere-specific enzyme activity during secondary grassland succession in the Loess Plateau, China

Dynamics of soil enzyme activity during plant restoration processes have been studied extensively; however, a general understanding of the rhizosphere-specific enzyme activity during plant secondary succession is limited. Rhizosphere samples were collected from the dominant and main companion species in farmlands abandoned for up to 32 years in the Loess Plateau. We determined soil chemical properties, phospholipid fatty acid (PLFA) profiles and activities of four enzymes (beta-1,4-glucosidase, BG; beta-1,4-N-acetylglucosaminidase, NAG; L-leucine aminopeptidase, LAP and alkaline phosphatase, AP), specific enzyme activity per soil organic carbon (SOC) and per PLFA unit. Specific BG, NAG, LAP and AP activities per SOC unit significantly decreased 77.1%, 53.2%, 83.0% and 49.2% with plant succession. Specific BG, NAG and LAP activities per PLFA unit significantly decreased 59.6%, 18.9% and 70.9% with plant succession. Furthermore, specific BG and LAP activities in the dominant species were lower than those in the companion species. Redundancy analysis revealed that variations in specific enzyme activities per SOC and per PLFA unit were explained 76.6% and 68.6% by soil chemical properties. SOC, total nitrogen (TN) and available phosphorus (aP) significantly influenced the rhizosphere-specific enzyme activities. This study improved the understanding of the element cycle at the root-soil interface under secondary succession ecosystems.