祁连山南坡土壤侵蚀定量研究与影响因素分析

土壤侵蚀是引起土壤土地退化及土壤肥力下降的主要原因之一,直接影响着区域生态经济的可持续发展。基于RUSLE模型、CA-Markov模型及LMDI模型,对祁连山南坡2000—2019年土壤侵蚀空间变化及预测、不同地形条件下土壤侵蚀变化特征及影响因子的定量分析进行了研究,为研究区水土保持治理提供参考。研究表明:(1)土壤侵蚀模数呈现出西北向东南递减的趋势,整体增加速率为0.0645/a;(2)土壤侵蚀变化分为两个阶段,2000—2005年为土壤侵蚀加重阶段,2005—2019年为土壤侵蚀减轻阶段;(3)2019—2027年,土壤侵蚀虽有减轻的趋势,但也要防止极强度以下的侵蚀低级向高级转变;(4)土壤侵蚀模数随着海拔及坡度的增加而增加,在海拔4 700～5 200 m及坡度>30°的区域土壤侵蚀模数达到最大,分别为10 460.72,7 256.32 t/(km²·a)。土壤侵蚀量随着坡度的增加而减小,不同坡向下的土壤侵蚀排序为西>北>南>东>水平方向;(5)植被对土壤侵蚀的影响一定是积极的,而降雨不一定加重土壤侵蚀,且土壤侵蚀受植被和降雨影响较小区域主要分布在门源县。综上,祁连山南坡的土壤侵蚀近几年得到较好的治理,可根据具体的环境条件对土壤侵蚀进行分类治理。

Quantitative Study on Soil Erosion and Its Influencing Factors on the South Slope of Qilian Mountain

Soil erosion is one of the main causes of soil degradation and soil fertility decline, which directly affects the sustainable development of regional ecological economy. Based on RUSLE model, CA Markov model and LMDI model, we studied the spatial change and prediction of soil erosion on the south slope of Qilian Mountain from 2000 to 2019, and the quantitatively analyzed the soil erosion change characteristics and influencing factors under different topographic conditions, so as to provide reference for soil and water conservation and control in the study area. The results show that:(1)the soil erosion modulus decreased from northwest to southeast, and the overall increase rate was 0.064 5/a;(2)the change of soil erosion could be divided into two stages: 2000—2005 was the aggravation stage of soil erosion, and 2005—2019 was the mitigation stage of soil erosion;(3)from 2019 to 2027, although soil erosion tended to reduce, it was also necessary to prevent the transformation from low-level to high-level erosion below extreme intensity;(4)the soil erosion modulus increased with the increase of altitude and slope; the soil erosion modulus reached to the maximum in the area with altitude of 4 700～5 200 m and slope>30°, which were 10 460.72 and 7 256.32 t/(km²·a), respectively; the amount of soil erosion decreased with the increase of slope, and the order of soil erosion in different slope directions was west>north>south>east>horizontal direction;(5)the impact of vegetation on soil erosion must be positive, while rainfall does not necessarily aggravate soil erosion, and soil erosion is less affected by vegetation and rainfall, which is mainly distributed in Menyuan County. In conclusion, soil erosion on the southern slope of Qilian Mountains has been well controlled in recent years, and soil erosion can be classified and controlled according to specific environmental conditions.