疏勒河上游土壤磷和钾的分布及其影响因素

Distributions pattern of phosphorus,potassium and influencing factors in the upstream of Shule river basin

土壤中磷和钾是植物不可缺少的营养元素,研究它们的含量及其分布规律对高寒草地的可持续发展和区域土壤碳氮循环的认识均具有重要意义。以疏勒河上游13处生态观测样地(7种土壤类型)为研究对象,结合土壤有机碳、全氮、粒径和pH等理化性质和气象因子,分析了不同土壤类型表层和剖面中土壤磷、钾分布特征及其影响因素。结果表明:0—20 cm表层土壤全磷、有效磷、全钾和有效钾平均含量分别为(0.50±0.14)g/kg、(2.69±1.61)mg/kg、(14.84±0.59)g/kg和(151.03±117.57)mg/kg。表层土壤全磷含量与年均气温和土壤粉粒含量呈显著正相关,而与年均降水量呈显著负相关;表层土壤有效磷含量与有机质、全氮呈显著正相关;表层土壤有效钾含量与土壤粉粒含量和年均气温呈显著正相关。全磷、有效磷、全钾和有效钾密度主要集中在0—40 cm的土壤层,它们均随着土壤深度的增加而逐渐降低。不同深度土壤全磷的总密度与年均气温均呈显著的正相关,其相关系数随着土层深度逐渐增加。温度和降水是影响表层全磷含量和分布的主要环境因子;土壤全钾含量受成土母质影响,变异性不大。该区域土壤中有效磷和有效钾相对缺乏,草地管理措施是影响它们变化的重要因素之一。气温是该区域土壤全磷和全钾密度分布的主控因子。

Soil phosphorus （P） and potassium （K） are indispensable elements of plant growth, and their content change could affect biogeochemical cycles of carbon, nitrogen, and other elements. The study of spatial and vertical distributions of soil P and K is crucial for the sustainable development of alpine grassland. Further, it is critical to understand regional mechanisms of biogeochemical cycles of soil carbon, nitrogen, and other elements. Thirteen typical ecosystem plots （including seven soil types） were selected, and two or three soil profiles from each plot were investigated. This study occurred during the summers of 2010 and 2011 in the upstream of the Shule river basin on the northeastern margin of the Qinghai-Tibetan Plateau. Distributions of soil P and profiles were studied. These elements were studied by K, their influencing factors on topsoil （0--20 cm）, and the soil analysis of soil P and K contents, other soil properties （ such as soil organic carbon, total nitrogen, pH value, and so on） , and meteorological factors （mean annual temperature and mean annual precipitation）. The results showed that soil total P, available P, total K, and available K contents in topsoil were （0.50±0.14） g/kg, （2.69±1.61 ） mg/kg, （ 14.84±0.59 ） g/kg, and （ 151.03±117.57 ） mg/kg, respectively. The correlation matrix of the variables showed that there were significant positive correlations between total P contents in the topsoil, mean annual temperature, and soil silt proportions. However, there was a significant negative relationship between total P contents in the topsoil and mean annual precipitation. Meanwhile, there were significant positive relationships between available P, soil organic carbon, and total nitrogen. There was a significant positive relationship between soil available K, soil silt content, and mean annual temperature. The densities of total P, available P, total K, and available K mainly concentrated in the 0--40 cm soil depth, and showed a decreasing trend with soil depth increase. Total P densities at different soil depths had a positive correlation with mean annual temperature, which increased with soil depth. Our study indicated that air temperature and precipitation were the main influencing factors for soil total P contents in topsoil and its spatial distribution. Because of similar soil parent material, small variances of total K in topsoil for the seven soil types were observed. The content of available P and available K contents could not meet plant growth need, and grassland management is an important factor for content change. Air temperature is the main control factor for total P and K densities in this study area. These results could provide fundamental data to clearly identify the P and K content status in alpine grassland soils. This, in turn, could provide new insights with which to understand the biogeochemical cycles and mechanisms of soil P, K, carbon, and nitrogen in alpine grassland ecosystems.