贺兰山不同海拔植被下土壤团聚体分布及其稳定性研究

以贺兰山不同海拔植被下0—20,20—40 cm土层土壤为研究对象,分析不同粒径团聚体含量及团聚体稳定性随海拔升高的变化特征,探讨其与土壤理化性质之间的相关关系。结果表明:0—20 cm土层,0.25~0.053 mm团聚体为主要团聚体类型,随海拔增加,水稳性大团聚体(>0.25 mm)含量增加,<0.053 mm团聚体含量减少,表明土壤团聚体随海拔增加呈现由小粒径向大团聚体转变的趋势。20—40 cm土层,水稳性大团聚体含量在中海拔(2139 m)达到最高,占比为65.73%。平均重量直径(MWD)和几何平均直径(GMD)在0—20,20—40 cm土层均呈现随海拔升高先增加后减小的趋势,并在2139 m处达到峰值。不同海拔梯度土壤团聚体MWD和GMD与土壤有机碳(SOC)、全氮(TN)、全磷(TP)粉粒以及砂粒含量呈正相关,与黏粒含量、pH呈负相关。贺兰山不同海拔植被下土壤团聚体稳定性总体表现为中海拔>高海拔>低海拔,较高含量的大团聚体和土壤养分是团聚体稳定的关键要素。

Study on Distribution and Stability of Soil Aggregate Under Vegetation at Different Elevations in Helan Mountains

The soil of 0—20 and 20—40 cm layers under different vegetations along an elevation gradient of Helan Mountains were investigated.We analyzed the variation characteristics of aggregate content of different particle sizes and aggregate stability with the increasing elevation,and explored the correlation between soil physicochemical properties and aggregate stability.The results showed that 0.25~0.053 mm aggregates were the main aggregates in 0—20 cm soil layer.With the increases in elevation,the contents of water-stable macroaggregates(>0.25 mm)increased,and the contents of<0.053 mm aggregates decreased,indicating that the soil aggregates changed from small particle size to large aggregates with the increasing elevation.In the 20—40 cm soil layer,the contents of water-stable macroaggregates reached the highest at mid-elevation(2139 m),which was 65.73%.The mean weight diameter(MWD)and geometric mean diameter(GMD)at both 0—20 and 20—40 cm soil layers increased first and then decreased with the increasing elevation,with the peak value at 2139 m.The MWD and GMD of soil aggregates in different elevation gradients were positively correlated with soil organic carbon(SOC),total nitrogen(TN),total phosphorus(TP),silt and sand content,and negatively correlated with clay content and pH.These results suggestted that the overall stability of soil aggregates along the elevations of Helan Mountains were ranked as medium elevations>high altitude>low altitude.Higher content of macroaggregates and soil nutrients contributed to the stability of aggregates.