Impact of vegetation community succession on available N, P and enzyme activity of the soil in karst hill of Guizhou Province

Available N, P and enzyme activity of soils in different vegetation are estimated with vegetation community succession in Maolan of Guizhou Province by investigating and analyzing on the soils. The results show that the contents of total N and available organic P slightly reduce but the contents of available N, NO3--N, available P and water-soluble P had significantly decrease in surface soil (0~15 cm) following the process from broad-leaved forest to shrub forest and shrub grass. The average decreasing amount in the con tents of available N, nitric nitrogen and available P as well as the water-soluble P in the soils under shrub grass is 28.09%, 65.44%, 69.42% and 81.71%, respectively; meanwhile, the average contents of urease, proteinase and alkalin phosphatase in the shrub grass soil reduces by 74.72%, 63.08% and 50.32% respectively in comparison with that under primeval broad-leaved forest. Thus, the variations of soil available N and P in karst hill significantly affected by vegetation community succession, and forest degradation mainly leads to obvious decrease in the amount of nitric nitrogen and water-soluble P in the soils.