Soil and water loss and ecological risk assessment in southeastern Tibet of southwestern China

  Objective  This paper aims to analyze the spatial and temporal characteristics of soil and water loss in southeast area of Tibet of southwestern China, and to conduct a comprehensive assessment of soil and water loss ecological risk, with a view to providing a theoretical basis and scientific guidance for the prevention and control of soil and water loss in southeast area of Tibet.

  Method  The USLE model was used to estimate the soil erosion modulus and erosion sensitivity index for year 2014, 2017 and 2020 in the study area; then a comprehensive assessment of the ecological risk of soil erosion in southeast area of Tibet was conducted based on precipitation, soil, vegetation cover, sensitivity index and other indicators.

  Result  (1) The overall soil erosion in southeast area of Tibet was relatively low, and the soil erosion grades were mainly composed of very slight erosion and light erosion, which accounted for about 95% of the study area, the very slight erosion area showed the trend of developing into the light erosion area gradually. (2) From 2014 to 2020, the highest value of the sensitivity index of regional soil and water loss fluctuated around 3.0, which increased in 2017 and decreased slightly in 2020, with little change in the overall value. The high value areas were mainly distributed in the Alpine ice-snow covered areas, the low value areas were mainly distributed in the high vegetation coverage areas. (3) The ecological risk index of soil and water loss in southeast area of Tibet ranged from 1.2 to 4.2. The high risk area was mainly distributed in the subtropical rainforest area in the southwest of the study area, and the low risk area was mainly distributed in the northeast plateau meadow area. The risk grade of soil and water loss fluctuated on the whole, but it should be noted that the proportion of high risk area increased gradually.

  Conclusion  The soil and water loss in southeast area of Tibet is at a low level, and the effect of soil and water conservation in southwest and northeast area of Tibet is good. However, the ecological risk index of soil and water loss in southwest of the research area is at a high level, therefore, these areas still need to do a good job of soil and water conservation protection, to ensure the safety of regional ecological environment. The effect of soil and water conservation in the northwest to southeast region of the study area is relatively poor, so it is necessary to strengthen the control of soil and water loss, such as carrying out vegetation restoration or taking engineering measures.