Change characteristics of soil microbial phosphorus， alkaline phosphatase and phytase under different vegetation types in karst area

【Objective】 To study the changes of phosphorus（MBP）， alkaline phosphatase（ALP） and phytase（PHY）in soil microorganisms under different vegetation types in karst areas， and the change of soil phosphorus availability， in order to provide a reference for improving the current situation of phosphorus stress in karst area.【Method】The five planting cover types of cultivated land，grassland，garden，shrub，forest and different soil layers（0-5 cm，5-10 cm，10-20 cm， 20-30 cm and 30-40 cm）in karst area were taken as the research object. The content of MBP and activities of ALP and PHY in microbial biomass of different vegetation types were compared，the correlation between the three factors and available phosphorus and soil environmental factors was revealed by establishing regression equation and redundancy analysis.【Result】The MBP content，ALP and PHY activities of different vegetation types decreased gradually with the increase of soil depth. The results showed that，the MBP content in 0-5 cm soil layer of shrub soil（25.08 mg/kg）was significantly higher than that of other vegetation types except 0-5 cm layer of forest soil（23.63 mg/kg）（P＜0.05，the same below）. Among the 5 vegetation types，the highest ALP activity was 101.96 mg/ （g·d）in the 0-5 cm soil layer of forest soil，and there were no significant differences among vegetation types in the 20-40 cm soil layer （P＞0.05）. There were significant differences in PHY activity of shrub，grassland and garden soils in 0-5 cm and 20-40 cm soil layers. Under the influence of different vegetation types，soil MBP，ALP and PHY were positively correlated with soil available phosphorus. Soil MBP，ALP and PHY were extremely significantly positively correlated with total nitrogen，organic matter，alkali-hydrolyzed nitrogen，total phosphorus and sand（P＜0.01，the same below），and the contribution rate of organic matter was the highest. There was significant or extremely significant negative correlation with bulk density and clay particles. 【Conclusion】The content of MBP，activities of ALP and PHY and their distribution in soil are affected by vegetation restoration type and ecological environment in karst area. Shrub and forest soils have high phosphorus utilization rate and rich phosphorus sources，while cultivated land has low phosphorus utilization rate and the source was single，which are positively correlated with soil available phosphorus. Organic matter are the key environmental factors affecting soil MBP， ALP and PHY in karst area.