Spatiotemporal Variations and Causes of Wind/Rainfall Erosion Climatic Erosivity in Qinghai Province, China

Wind and rainfall climatic erosivities are important parameters with which to assess the possible effects of climatic conditions on erosion. In this study, wind erosion climatic erosivity (C-factor) and rainfall erosivity (Rday-factor) were calculated for the period 1970–2020 based on data from 50 meteorological stations in Qinghai Province. The Mann–Kendall test, trend analysis, and K-means clustering method were used to explore the spatiotemporal characteristics of regional wind/rainfall climatic erosivity. Results showed that the annual mean value of the C-factor was 25.8 over the past 51 years, with an obvious trend of decline of 6.5/10a. The mean annual value of the Rday-factor was 491.6 MJ·mm/(hm2·h·a), with an obvious trend of increasing of 24.0 MJ·mm/(hm2·h·10a). Strong seasonality was found in both the C-factor and the Rday-factor. The highest values of the C-factor were found in late winter and spring, accounting for a substantial proportion of the annual C-factor (48.6%). Rainfall erosivity occurred mainly April–October, with the highest values in summer, accounting for a substantial proportion of the annual Rday-factor (72.9%). Wind-erosion climatic erosivity and rainfall erosivity were obviously asynchronous on an annual basis, and the period of their combination extended the time of soil erosion. Through k-means clustering analysis, climatic erosivity in Qinghai Province was divided into three regions: the first dominated by wind-erosion climatic erosivity, the second dominated by rainfall erosivity, and the third dominated by their combination. The most serious land erosion occurred in the third region, accounting for 34.3% of the entire land area of Qinghai Province, where annual rainfall was found to be broadly consistent at 300–400 mm. Wind speed, temperature, rainfall, and sunshine duration are key factors known to impact the variation in wind-erosion climatic erosivity, while annual erosive rainfall, number of rainy days, and sunshine duration are the main factors known to impact the variation in rainfall erosivity. The findings of this study represent a robust reference for ecoenvironmental protection, sustainable development, and soil protection.