土壤有机碳氮和生物量对高寒草甸放牧压力的响应

Effect of soil organic carbon and nitrogen and biomass on grazing pressure on Alpine meadow

采用野外采样与室内分析测定相结合的方法,选取了果洛大武地区四种放牧梯度样地为研究对象,设置了0～10cm、10～20cm、20～30cm三个土层,对土壤有机碳、全氮、速效氮、生物量进行比较研究。研究表明:同一放牧压力,土壤有机碳、全氮、速效氮含量和地下生物量随着土层的加深而减少,地上生物量由高到低依次为放牧梯度2>放牧梯度3>放牧梯度4>放牧梯度1,且土壤有机碳呈现规律性变化,其顺序为放牧梯度1 <放牧梯度4 <放牧梯度2 <放牧梯度3;在20～30cm土层中,放牧梯度3的全氮含量显著高于其他三个放牧梯度(P <0. 05),而其他三个放牧梯度的含量差异不显著(P> 0. 05);另外两个土层的全氮含量变化不明显(P> 0. 05)。0～10cm土层中,放牧梯度1和放牧梯度3的速效氮含量差异显著(P <0. 05);10～20cm、20～30cm土层中,放牧梯度1速效氮含量显著低于其他三个放牧梯度(P <0. 05),而其他三个放牧梯度的含量差异不显著(P> 0. 05)。0～10cm土层中,放牧梯度4的地下生物量与其他三个放牧梯度差异显著(P <0. 05),而另外三个放牧梯度之间没有显著差异(P> 0. 05);10～20cm、20～30cm土层的地下生物量差异不显著(P> 0. 05)。

On the basis of field investigation and laboratorial analysis, the soil organic carbon, total nitrogen, available nitrogen and biomass in the 0 - 10cm, 10 - 20cm, 20 - 30cm soil layers of four different grazing degrees in Dawu region of Guoluo Prefecture was analyzed. The results showed that on the condition of the same grazing pressure, soil organic carbon, total nitrogen, available nitrogen and underground biomass decreased with the soil depth increasing; the aboveground biomass varied in the order grazing gradient Ⅱ 〉 grazing gradient Ⅲ〉 grazing gradient Ⅳ 〉 grazing gradient Ⅰ, with values of 187.5, 169.16, 126.44 and 116.81g/m^2 respectively. The soil organic carbon contents of gradient Ⅲ was significantly（P 〈 0.05） higher than the gradient Ⅰ of each soil layer, and the distribution of soil organic carbon contents was in order grazing gradient Ⅰ 〈 grazing gradient Ⅳ 〈 grazing gradient Ⅱ 〈 grazing gradient Ⅲ. In the 20 - 30cm soil layer, total nitrogen contents of gradient Ⅲ were significantly（P 〈 0.05 ）higher than in the other three gradients, but the other three gradients were not significantly different （P 〉 0.05 ） ; total nitrogen of the other two layers was not significantly different（P 〉0.05）. In the 0 - 10cm soil layers, available nitrogen contents of gradient Ⅰ and gradient Ⅳ were significantly different（P 〈0.05）. in the 10 - 20cm, 20 -30cm soil layers, available nitrogen contents of gradient Ⅰ were significantly （ P 〈 0.05 ） lower than in the other three gradients, but the other three gradients were not significantly different（P 〉 0.05 ）. In the 0 - 10cm soil layer, underground biomass of gradient Ⅳ and the other thine gradients were significantly different （ P 〈 0.05 ） , but no significance difference were found among other thine gradients（P 〉0.05）. The underground biomass of the 10 - 20cm, 20 - 30cm soil layers were not signifi- cantly different （ P 〉 0.05 ）.