Comprehensive Evaluation On Soil Characteristics Of Different Plantations In Karst Mountain Sites

Degradation of soil quality has been an essential ecological enviroment concern in rocky desertification sites of Karst region. Artificial afforestation can not only conserve soil and water but also meliorate soil quality in Karst forest ecosystem. The thesis taking five types of plantations:locust (Robinia pseudoacacia-8a; RP8); Yunnan cypress(Cupressus duclouxiana-8a,12a,18a; CD8,CD12,CD18); pure and mixed stands of locust and Yunnan cypress (R.pseudoacacia-Cupressus duclouxiana-8a; RD8) and the controlling land (non-plantation area) as the research objects at Puding county, Guizhou province, discussed the dynamics of soil physical and chemical properties and enzyme activities and correlation between soil enzymatic activities and other factors, and then evaluated the soil quality of different types of plantations by adopting soil integrated quality index (SQI). The chief results were as follows:(1) Soil physical properties were meliorated obviously after artificial afforestation. Soil bulk density decreased, and soil total porosity, capillary porosity, non-capillary porosity, non-capillary porosity/capillary porosity (NCP/CP) and field moisture capacity increased, respectively.(2) Soil water properties such as soil water content, water capacity and water absorption rate all presented the similar order either in different types of plantations or in different ages of Yunnan cupressus stands. Logarithmic function and exponential function could describe dynamic characteristics.(3) The dynamic variations of soil available nutrients were different remarkably (p<0.01) but the changes of enzyme activities determined under six sites had a similar tendency throughout the study and associated with soil water content. Statistical analysis showed that there existed an interdependency and interaction between soil physical and chemical properties and soil enzyme activities.(4) Comparisons of soil integrated quality index (SQI) of different types of plantations indicated the relative order of soil quality as follows:RP8> CD12> RD8> CD8> CK> CD18, the SQI were 0.353,0.263,0.164,0.004, and -0.091 respectively taking CK as benchmark.