The Relationship Between Plant Community And Soil Nutrients Features Of Alpine Steppe At Different Degradation Degrees In Qinghai-tibetan Plateau

1 The plant community features at different degradation degrees of alpine steppeThis study showed that the dominant plant was Carex. moorcroftii at the non-degraded alpine steppe, and was replaced by the coexistence of Kobresia pygmaea and C. moorcroftii at the lightly and moderately degraded degree, while Polygonum viviparum and Sanguisorba arenaria were dominant plant as the alpine steppe was at highly degraded degree. With the degradation of alpine steppe, the hygrophytes decreased, and the mesophytes and xerophytes increased in this study. The richness index and diversity index firstly increased and then decreased as the alpine steppe degraded, peaking at the moderately degraded degree. Although the cover, height and aboveground biomass of plant community decreased, the aboveground biomass of Gramineae and Leguminose plants firstly increased and then decreased in the degradation process of alpine steppe, peaking at the moderately degraded degree, therefore the total productivity is controlled by Cyperaceae, Leguminose and forbs biomass, and not controlled by Gramineae biomass at different degradation degrees of alpine steppe in the hinterland region of Qinghai-Tibetan Plateau. 2 The species features at different degradation degrees of alpine steppeBased on the studies mentioned above, the change of plant component of alpine steppe due to the ability of competing and using resources of different species. These abilities of the plant of Cyperaceae were decreased, while the plant of forbs increased in the degradation process of alpine steppe. Because of the biological characteristics of dominant species, their abilities of competing and using resources were different among different plant species. 3 The soil nutrient features at different degradation degrees of alpine steppeWith the degradation of alpine steppe, soil organic carbon, total N, available N, available P and available K gradually degreased; Total P first increased and than decreased, the peaking was at the moderate degradation degree; Total K was not significantly influenced at different degradation degrees of alpine steppe. Compared with other grassland, the P of alpine steppe was deficient, suggest that adding P in the degradation process of alpine steppe. 4 The correlation between plant community feature and soil nutrient features at different degradation degrees of alpine steppeWith the degradation of alpine steppe, plant community feature was mainly influenced by 0-10 cm soil nutrient. The plant diversity was significant influenced by soil P; Plant total biomass, Cyperaceae biomass and forbs biomass mainly controlled by soil organic carbon, total N, available N, available P and available K, Leguminose biomass was mainly influenced by soil P, and Gramineae biomass was mainly influenced by soil N; Soil nutrient was significantly influenced. 5 The correlation between main palnt species features and soil nutrient features at different degradation degrees of alpine steppeWith the degradation of alpine steppe, C. moorcroftii and K. pygmaea were significantly inlunced by soil organic carbon, total N. Total P, C. moorcroftii was significanglty inlunced by soil available P, while K. pygmaea was significanglty inlunced by soil available N and available K. The ability of using the soil nutrient was increased with decreasing the contend of soil nutrient.