长江源区高寒草地土壤有机质和氮磷含量的分布特征

土壤养分是高寒草地生态系统维系健康的基础。本研究分析了长江源区沼泽化草甸、典型草甸、草原化草甸和沙生草地的土壤养分特征,以期为高寒草地合理管理提供理论依据。研究表明,不同类型高寒草地的土壤有机质和全氮含量存在明显的差异,表现为沼泽化草甸＞典型草甸＞草原化草甸＞沙生草地,土壤有机质和全氮含量在各个草地类型内均随着土层深度增加而显著降低(P＜0.05);土壤速效氮含量为草原化草甸＞典型草甸＞沼泽化草甸＞沙生草地,草原化草甸含量高达65.5 mg·kg-1,而沙生草地含量仅为11.5 mg·kg-1,除沙生草地外,其他草地类型土壤速效氮含量最大值出现在10-20 cm土层;土壤全磷和速效磷含量在高寒草甸不同退化演替阶段及其各土层中差异不显著(P0.05);高寒草甸退化演替过程中,土壤养分各因素间相互影响,其中,土壤全氮、全磷、速效氮和速效磷与土壤有机质之间呈显著正相关关系,土壤速效氮与全氮和土壤速效磷与全磷之间亦呈显著正相关关系,而土壤pH值与土壤各养分之间的相关性均不显著。

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.