[Soil N/P ratio distribution characteristics of alpine grassland ecosystem in Qinghai-Tibet Plateau].

The distribution characteristics of soil N/P ratio in alpine grassland ecosystem of Qinghai-Tibet Plateau were surveyed by field investigation and laboratory analysis.Horizontally,soil N/P ratio was generally higher in west and lower in east in a manner of staggered patch distribution,with higher N/P ratios mainly centralized in the hinterland of northern part of Tibet Plateau and in the lake basin area of the northern foot of Himalayas.Significant differences in soil N/P ratio were observed among grassland types and natural transects.Vertically,the distribution of N/P ratio along the soil profile from aboveground to underground among different grass types could be categorized into five patterns,including low-high-low-high,low-high-low,low-high,high-low-high-low,and high-low-high.The N/P ratio showed a significant positive correlation with soil bulk density at 0-20 cm depth,soil water content at 20-30 cm depth,contents of soil available K and total nitrogen,respectively.However,it showed significant negative correlation with soil bulk density at 20-30 cm depth,contents of soil available P and total P,respectively.