Background North-south Pan Rivers are the main rivers in the upper reaches of the Pearl River, and the watershed is one of the areas with the most serious soil and water loss in the Pearl River Basin. Analysis on spatial and temporal dynamics of soil erosion in this watershed may provide scientific support and theoretical basis for soil and water conservation construction and will benefit regional sustainable development.

Methods Based on multi-source remote sensing data, meteorological data, ecosystem types data, soil properties data, Normalized Difference Vegetation Index (NDVI) and Digital Elevation Model (DEM) data, the Revised Universal Soil Loss Equation (RUSLE) was used to analyze the spatial and temporal variation of soil erosion in North-south Pan River watershed from 2000 to 2010. To improve the accuracy of simulation results, parameters in the RUSLE model were amended according to local environment and achievements of previous researches. Meanwhile, the driving factors of soil erosion change were discussed from the perspectives of precipitation and vegetation coverage.

Results Average soil erosion modulus in North-south Pan River watershed was 14.6 t/(hm²·a) during 2000-2010, and annual soil erosion amount was about 118×10⁶ t/a. In the period from 2000 to 2010, soil erosion modulus decreased with the annual variation of-0.87 t/(hm²·a·a), and the area of unapparent soil erosion increased apparently by 1 076 km² each year, while local area still showed a certain increasing trend on soil erosion, which accounted for about 22.8% of the total area. The areas with decreasing soil erosion mainly concentrated in the northern, southwestern and southeastern part of the watershed, and areas with increasing soil erosion mainly concentrated in the eastern and the southern part of the watershed. The change of soil erosion in the North-south Pan River watershed was mainly caused by joint effect of ecological engineering and climate change. The increase of vegetation coverage benefitting from the implementation of ecological engineering in this watershed better protected the soil from erosion. Meanwhile, the decrease of rainfall erosivity weakened the external force of soil erosion and helped prevent the formation of soil erosion. In addition, the Grain for Green Project led much sloping field change to forest and grass, and this land use change contributed to the soil retention a lot.

Conclusions It is critical to take effective measures to protect the soil from erosion. Although the soil erosion has been alleviated, the ecological situation of the North-south Pan River watershed is still fragile on the whole, especially in Guizhou province. To further curb the occurrence of soil erosion thoroughly in this watershed, protection should be strengthened and more precise, especially in steep slope area. Meanwhile, a long-term mechanism of ecological protection needs to be established and the achievement of early water and soil erosion governing should be consolidated.