牦牛放牧率和放牧季节对小嵩草高寒草甸土壤养分的影响

Effects of stocking rate and grazing time of yaks on soil nutrient contents in Kobrecia parva alpine meadow

经过两年牦牛放牧试验表明,夏季草场不同土壤层有机质、有机碳、全磷、全氮和速效磷的含量及0～20cm土壤层营养因子的平均含量与放牧率呈线性回归关系,速效氮含量与放牧率呈二次回归关系;冬季草场不同土壤层有机质、有机碳和全氮与放牧率呈线性回归关系,全磷、速效磷和速效氮的含量及0～20cm土壤层营养因子的平均含量与放牧率呈二次回归关系。随着放牧率的逐渐增加,夏季草场不同土壤深度速效氮含量也逐渐减小,当放牧率达到1.07、1.08和1.22头·hm-2时,0～5、5～10、10～20cm土壤速效氮含量依此达到最小;冬季草场不同土壤层全磷、速效磷和速效氮含量逐渐增加,当放牧率达到0.81、0.78和1.00头·hm-2,1.03、1.09和1.03头·hm-2,1.36、1.35和1.30头·hm-2时,0～5、5～10、10～20cm土壤层全磷、速效磷和速效氮含量分别依此达到最大。在夏季草场,0～20cm土壤层速效氮平均含量达到最小放牧率是1.07头·hm-2;冬季草场0～20cm土壤层全磷、速效磷和速效氮含量达到最大放牧率分别是0.90、0.83和1.21头·hm-2。

The results of grazing trial about yaks for two years showed that in summer,contents of different soil stratums and average contents of 0～20cm stratum for organic matter (OM),organic carbon (OC),total nitrogen (TN),total phosphorus (TP) and available phosphorus (AP) were negatively correlated with stocking rate with a linear regressive relationship,while it was quadratic regression between contents of available nitrogen (AN) and stocking rate.In winter,contents of different soil stratums and average contents of 0～20cm stratum for OM,OC,TN were negatively correlated with stocking rate linearly,while those of TP,AP and AN were quadratically correlated with stocking rate.In summer pasture,with the increase of stocking rate,contents of AN for different stratums decreased with depth.When stocking rate was 1.07,1.08 and 1.22 heads·hm^(-2) respectively,contents of AN for 0～5 cm,5～10 cm and 10～20 cm in sequence reached the minimum value.In winter pasture,contents of TP,AP and AN for 0～5 cm,5～10 cm and 10～20 cm,respectively reached the maximum value when stocking rate was 0.81,0.78 and 1.00 heads·hm^(-2),1.03,1.09 and 1.03 heads·hm^(-2),and 1.36,1.35 and 1.30 heads·hm^(-2),respectively.In addition,in summer pasture,average contents of AN for 0～20 cm soil stratum reached the minimum value when stocking rate was 1.07 heads·hm^(-2),while contents of TP,AP and AN were the maximum at 0.90,0.83 and 1.21 heads·hm^(-2) respectively in winter pasture.