Distribution characteristics of soil organic matter and nitrogen, phosphor content in alpine grassland ecosystem in upper Yangtze River

Soil nutrient is the basis for maintaining alpine grassland ecosystem health. The distribution characteristics of soil nutrient for swamp meadows, typical meadow, steppe meadow and sandy grassland were studied to provide theoretical basis for reasonable management of alpine grassland. The results demonstrated that (1)obvious difference was detected for soil organic matter and total nitrogen content between different type alpine grassland ecosystems, and swamp meadows＞typical meadow＞steppe meadow＞sandy grassland. Moreover, soil organic matter and total nitrogen content showed a significant decrease trend with the increase of soil depth in all the studied alpine grassland ecosystems. (2) The soil available nitrogen content in steppe meadow was as high as 65.5 mg·kg-1, which was greater than those of the other three grassland ecosystems. In contrast, the soil available nitrogen content in sandy grassland was as low as 11.5 mg·kg-1, which was the least one. The soil available nitrogen content in typical meadow was greater than that in swamp meadow. Furthermore, the maximum value of soil available nitrogen among different alpine grassland ecosystems appeared in 10―20 cm soil layer except for the sandy grassland. (3) No significant difference for soil total phosphorus and available phosphorus were detected between different degradation periods of alpine grassland ecosystems as well as different soil layers of the same alpine grassland ecosystems. (4) Different soil nutrients could influence each other in the degradation process of alpine grassland ecosystem. A significant positive correlation was found between soil organic content and soil total total nitrogen, total phosphorus, available nitrogen and available phosphorus, as well as between soil available nitrogen and total nitrogen. In addition, a significant positive correlation was detected between soil available phosphorus and total phosphorus. However, no significant correlation could be found for soil pH and soil nutrients.