退化高寒草甸土壤有机碳分布特征及与土壤理化性质的关系

Distribution of soil organic carbon and its relationship with soil physical and chemical properties on degraded alpine meadows

本研究对西藏当雄不同退化程度高寒草甸土壤有机碳分布特征及其与土壤理化性质演变进行分析，结果表明，土壤有机碳及有机碳密度均为正常草甸土壤〉轻度退化草甸土壤〉严重退化草甸土壤，且0～10cm土层中有机碳含量及其密度均高于10～20cm土层土壤。回归分析表明，土壤有机碳与土壤活性有机碳、土壤碱解氮、速效磷、速效钾及土壤含水量之间存在显著或极显著的正相关关系，其决定系数R。分别为0．9139、0．977l、0．9314、0．6653和0．7156，直线回归方程分别为y=0．0743x-0．0261，y=2．6768x＋14．4250，Y=0．2459x＋3．3479，Y=4．2965x＋71．6670，Y一0．7908x＋5．4245；而与土壤容重呈显著负相关关系（Y=-0．0167z＋1．5531）。土壤有机碳的损失，造成土壤养分和水分减少，土壤容重增大。通径分析表明，土壤有机碳的变化对碱解氮的影响最显著。

Soil organic carbon, soil active organic carbon, soil alkali-hydrolysable nitrogen, soil available phosphorus, soil available potassium, soil water content and soil bulk density were determined to study the distribution of soil organic carbon and soil physical and chemical properties on degraded alpine meadows in Dangxiong,Tibet. Results showed that the change orders of soil organic carbon content and its density both in the 0-10 cm and 10-20 cm soil layers were normal meadow〉slightiy degraded meadow〉serious degraded meadow; soil organic carbon content and its density in the 0-10 cm soil layer were higher than those in the 10-20 cm soil layer. There were correlations between soil organic carbon and other soil nutrients. The regression analysis showed that there were significantly positive linear relationships between soil organic carbon and soil active organic carbon （y-0. 074 3x-0. 026 1, R^2=0. 913 9）, soil alkali-hydrolysable nitrogen （y=2. 676 8 x-F14. 425 O, Rz =0. 977 1）, soil available P （y=0. 245 9x＋3. 347 9, R2- 0. 931 4）, soil available K （y=4. 296 5x-F71. 667 0, RZ=O. 665 3） and soil water content （y-=0. 790 8x -F 5. 424 5, R^A2-0. 715 6）,respectively. A significant negative linear correlation existed between soil organic carbon and soil bulk density （y=--0. 016 7x＋l. 553 1, RZ=0. 773 5）. The loss of soil organic carbon re- sulted in reduction of soil nutrients and moisture and increasing soil bulk density. Path analysis indicated that the change of soil organic carbon had the most significant effect on the soil alkali-hydrolysable nitrogen.