小嵩草高寒草甸土壤营养因子及水分含量对牦牛放牧率的响应 Ⅰ夏季草场土壤营养因子及水分含量的变化

Responses of contents of soil nutrient factors and water to stocking rates for yaks in Kobresia parva alpine meadow Ⅰresponses to contents of soil nutrient factors and water to stocking rates in summer pasture

两年的牦牛放牧试验结果表明 :随放牧率的增加 ,夏季草场各土壤层有机质、有机碳、全氮和全磷的含量呈下降趋势 ,它们的含量与放牧率呈显著的线性回归关系 ,速效氮的含量与放牧率呈二次回归关系 ,各土壤营养因子平均含量与放牧率也有类似的关系 .而且当放牧率分别达到 1.0 7heads/hm2 、 1.0 8heads/hm2 和 1.2 2heads/hm2 时 ,0～ 5 cm、 5～ 10 cm、 10～ 2 0 cm土壤速效氮含量依此达到最小 ,若放牧率继续增加 ,各土壤层速效氮的含量依此开始增加 ,而速效氮的平均含量达到最小的放牧率是 1.0 8heads/hm2 .在相同放牧率下 ,有机质和有机碳的含量在各土壤层之间差异极显著 P<0 .0 1 ,全磷差异显著 P<0 .0 5 ,全氮和速效氮差异不显著 P>0 .0 5 ,而且放牧率和土壤深度的交互作用对土壤各营养因子含量的影响极显著 P<0 .0 1 .放牧率对各土壤层的含水量有显著的影响 P<0 .0 5 ,不同年度间同一土壤层含水量的差异不显著 P>0 .0 5 .

Effects of stocking rates on contents of soil nutrient and water in summer pasture of alpine meadow had been studied for two years. The result showed that contents of organic matter, organic C, total N and total P decreased in the same stratum with the increase of stocking rates, and there was a significant linear regression relationship between their contents and stocking rates, the second degree polynomial regression between stocking rates and contents of available N, and then average nutrient contents of every nutrient factors (0~20 cm soil layer) had a similar response with contents of every stratum. And the contents of 0~5 cm, 5~10 cm, 10~20 cm soil layer for available N reached to the minimum values successively when stocking rates equaled to 1.64, 1.73 and 1.97 heads/hm^2 respectively, and stocking rate was (1.67) heads/hm^2 average contents of available N reaching to the peak value, and then contents of available N began increasing continually. Contents of organic matter, organic C were extremely significant difference in different stratums under the same stocking rates (P<0.01), significant difference for total P(P<(0.05)) and no significant difference for total N and available N (P>0.05), and the interactions of stocking rates and grazing time had an extremely significant effect on contents of every nutrient factor in different soil stratum (P<0.01). Besides, effect of stocking rates on water contents of every stratum was significant (P<0.05), the yearly change was not significant (P>05).