放牧季节及退化程度对高寒草甸土壤有机碳的影响

Effects of grazing season and degradation degree on the soil organic carbon in alpine meadow

高寒草甸是青藏高原的主要植被类型,本研究以青海省高寒草甸为研究对象,探讨不同放牧季节及退化程度下高寒草甸土壤有机碳含量及密度的分异特征。结果表明,在0-30 cm土层内,土壤有机碳含量随土层深度逐渐减小。土壤有机碳含量暖季放牧与冷季放牧之间无显著差异(P>0.05),且在不同土壤深度中一致。不同放牧季节下土壤理化性质及生物量各不相同。0-30 cm土层内,除0-5 cm未退化阶段土壤有机碳含量最高,其余各层土壤有机碳含量均在轻度退化阶段达到最大。土壤理化性质在不同退化阶段也变化各异,地下生物量随草地退化呈先增加后减小的趋势,而地上生物量随草地退化呈逐渐减小的趋势。冷季放牧高寒草甸土壤有机碳含量随草地退化呈逐渐减小的趋势,而暖季放牧土壤有机碳含量随草地退化呈先增加后减小的趋势。0-30 cm土层冷季放牧不同阶段土壤有机碳储量均低于暖季放牧,但未达到显著水平。可见,放牧强度的不同会对土壤有机碳的影响比放牧季节更大。

Alpine meadow is the major vegetation type in the Qinghai-Tibet Plateau. This study investigated the differences in soil organic carbon content and storage under different grazing seasons and degradation degree alpine meadow of Qinghai Province. The result of this study showed that soil organic carbon content decreased with the decrease of soil depth from surface to 30 cm depth,and it was not significantly different between cold-season grazing meadow and warmseason grazing meadow at 0 ― 30 cm soil layer. Soil physical properties and biomass at 0-30 cm soil layer varied with different grazing seasons. Soil organic carbon content was the biggest in non-degradation meadow at 0-5 cm layer and in the light-degradation meadow except for 0-5 cm layer. Soil physical properties varied with different degradation stages.The underground biomass increased at first and then decreased while the aboveground biomass decreased as the degradation degree of meadow increased. The soil organic carbon decreased within the cold-season grazing meadow while it in-creased at first and then decreased in the warm-season grazing meadow. The soil organic carbon density was lower in the cold-season grazing meadow than that in the warm-season grazing meadow but it was not significant. These results implied that the degradation degree played great impact on soil organic carbon.