肃北高寒草原不同放牧强度土壤养分变化特征

Study on Contents of Soil Nutrients in Different Grazing Intensities on Subei Alpine Steppes

研究了肃北高寒草原不同放牧强度下不同土层土壤养分及5种微量元素有效态含量变化特征。结果表明：①高寒草原土壤物理性质的变化对土壤养分及微量元素具有重要的调控作用;②随着放牧强度的提高,0~10、10~20 cm土层土壤体积质量均呈不同程度的增加,土壤孔隙度和土壤含水量则呈显著的递减趋势;③轻度放牧草地土壤有机质、土壤全N含量高于中度放牧和重度放牧草地;20~30 cm土层有机质随放牧强度的增大呈明显下降趋势,即随放牧强度的增大深层土壤肥力呈退化趋势;肃北高寒草原的速效养分以多N少P富K为特点,土壤速效N、P、K含量在总体上随放牧强度的增加呈下降趋势;④肃北高寒草原5种微量元素的高低顺序依次是：Na〉Fe〉Mn〉Cu〉Zn,不同放牧强度下各微量元素的变化一致,顺序依次是：轻度放牧〉对照〉中度放牧〉重度放牧;⑤放牧强度对10~20 cm的土层影响最大,随放牧强度的增大,地表植物营养吸收层土壤营养成分、微量元素呈降低,导致地表植被生长能力降低,最终导致地表土壤沙化,最后使草地大面积退化。

Na,Fe,Mn,Cu and Zn contents in soil samples in 0-10,10-20 and 20-30 cm layers in Subei alpine steppe were studied under four kinds of grazing intensities,i.e.,no grazing,light grazing,middle grazing and high grazing.The results indicated that： 1） grazing intensity had consistent effect on soil physical,chemical and biological fertilities,which were associated with each other and determined the evolution direction of soil fertility;2） With the increase of steppe grazing intensity,soil bulk density at both 0-10 cm and 10-20 cm layers increased,while soil porosity and moisture content decreased significantly,steppe grazing intensity influenced soil moisture content more strongly than soil porosity;3） Soil organic matter and total N contents of light grazing steppes were higher than those of middle grazing and high grazing steppes,soil available N,P and K contents increased with the increase of steppe standard of grazing intensity;4） The nutrient content order was NaFeMnCuZn,they shared the same changing order,i.e.,light grazingno grazingmiddle grazinghigh grazing;5） With the increase of steppe grazing intensity,the decreasing extent of soil nutrients was 10-20cm0-10cm20-30cm.