Karst is one of the weakest kinds of ecological environments and one of the main factors that restricts economic development in south-west China.And restoring vegetation and improving soil quality is among urgent affairs of the region.It is very important to explore the effects of different succession stages on soil quality for the restoration and management of karst degraded mountain.In this study,three succession stages in karst degraded mountain were selected at the Baimiao Mountain in Beibei of Chongqing.The three succession stages are grass stage,brush stage and forest stage.The paper reported the responses of 15 indicators including the Shannon-Wiener index,soil physical and chemical properties to the three succession stages.In addition,the index of soil quality was analyzed.Results showed that: different succession stages led to significant differences in the Shannon-Wiener index and soil physico-chemical properties.The soil quality of the three succession stages was ranked as follows: brush stage>forest stage>grass stage,and the same rule to the Shannon-Wiener index.In brush stage, soil bulk density,soil water,water holding capacity,capillary porosity,soil porosity and air porosity were significantly lower than those of two others,and soil organic matter,nitrogen and phosphorus as well.
Plant utilization of phosphorus in black calcareous soil was studied in Bidens pilosa, Mahonia fortunei and Cupressus funebris. Soil pH value, available phosphorus content, the distribution and transformation of inorganic phosphorus in rhizosphere and nonrhizosphere soils of these three plants were measured. Phosphorus content of plant was also measured and was 3 475, 2 609 and 3 466 mg·kg -1 in B. pilosa, M. fortunei and C. funebris, respectively. The pH value in rhizosphere soil was significantly lower （P<0.05） than that of nonrhizosphere in B. pilosa （7.35 compared with 7.47）, M. fortunei （7.47 compared with 7.67） and C. funebris （7.42 compared with 7.49）. Available phosphorus of B. pilosa was accumulated in rhizosphere soil, but those of the other two species in rhizosphere soil were decreased. Compared with the content in nonrhizosphere soil, the contents of Ca2P and （Ca8P+FeP+AlP） of B. pilosa in rhizosphere soil were increased by 0.89% and 2.13%, respectively, while the content of （Ca 10P+OP） was decreased by 3.03%, the total content of inorganic phosphorus of B. pilosa in rhizosphere soil was lower than that in nonrhizosphere soil. The content of （Ca8P+FeP+AlP） of C. funebris in rhizosphere soil was increased by 0.92%, while the contents of Ca2P and （Ca 10P+OP） were decreased by 0.09% and 0.83%, respectively. The total content of inorganic phosphorus of C. funebris in rhizosphere soil was lower than that in nonrhizosphere soil. The content of Ca2P of M. fortunei in rhizosphere soil was unchanged, the content of （Ca8P+FeP+AlP） was decreased by 1.29%, and the content of （Ca 10P+OP） was increased by 1.29%. The total content of inorganic phosphorus of M. fortunei in rhizosphere soil was higher than that in nonrhizosphere soil. The results showed that B. pilosa could decrease the pH value of the rhizosphere soil and activate （Ca 10P+OP）, elevate the level of available phosphorus, effectively absorb and accumulate phosphorus from the soil. Utilization of phosphorus i
