Response of soil extracellular enzyme activity to experimental precipitation in a shrub-encroached grassland in Inner Mongolia

Shrub encroachment has caused a vegetation shift in arid and semiarid grassland ecosystems around the world, leading to marked changes in ecosystem structures and functions. Soil extracellular enzyme activity (EEA) is an informative indicator of microbial decomposition and plays an important role in soil biogeochemical cycles, but it is unclear how shrub encroachment affects soil EEA, especially in the future precipitation pattern under climate change. In this study, we measured soil EEAs in a shrub-encroached grassland in Inner Mongolia, China, after four years of in situ experimental precipitation manipulation. Soil samples were collected from grass patches and shrub patches in four precipitation manipulation treatments (−30%, control, +30%, and +50%). Four soil enzymes involved in carbon cycling (α-glucosidase, AG; β-1,4-glucosidase, BG; β-D-cellobiosidase, CB; and β-xylosidase, XS), two nitrogen-acquiring enzymes (β-1,4-N-acetyl-glucosaminidase, NAG; and leucine amino peptidase, LAP), and one phosphorus-acquiring enzyme (acid phosphatase, AP) were investigated. The results showed that BG, XS, and LAP activities were significantly enhanced in shrub patches than grass patches (p