Spatial distribution characteristics of soil erodibility in Huangqian watershed of Shandong province

Background Soil is the main object of water erosion, and its inherent physical and chemical properties determine its ability to resist water erosion, thus affecting the size of water erosion intensity and the development of erosion process, which is usually measured by the K value in the world. The Huangqian watershed of Shandong province has a wide distribution of gardens and forests, but the terrain is undulating, with steep sloped being the majority and severe soil desertification. Studying the sensitivity of soil to erosion and finding out the spatial distribution characteristics of soil erodibility is of great significance to the soil erosion prediction and control in the Huangqian watershed of Shandong province.

Methods In this paper, the K value of soil erodibility was calculated through field soil sample collection, laboratory test and the EPIC model and modified by using the runoff plot observation data in the Huangqian watershed of Shandong province, and the spatial prediction and mapping and accuracy verification of the K value were conducted by sequential Gaussian simulation method comparing to the simple Kriging interpolation results, and the spatial differentiation characteristics of the K values were obtained and the effects of altitude and land use type on K were analyzed using spatial superposition analysis technique.

Results 1) The K values of 45 sample sites in this study area ranged from 0.0112 t·hm²·h/(MJ·hm²·mm) to 0.0456 t·hm²·h/(MJ·hm²·mm), with the average of 0.0334 t·hm²·h/(MJ·hm²·mm), indicating medium erodibility. The muddy sandy aquatic-brown soil and typical red clay were relatively high, but the difference of internal size between typical red clay and sandy acidic coarse bone soil is more obvious. 2) The K values of sequential Gaussian simulation with 200 times in this study area ranged from 0.0293 t·hm²·h/(MJ·hm²·mm) to 0.0436 t·hm²·h/(MJ·hm²·mm), with the average of 0.0367 t·hm²·h/(MJ·hm²·mm), which better solved the “smoothing effect” of the simple Kriging method and retained the data characteristics of the K values, and the root mean square error and mean absolute error were smaller than that of the simple Kriging method, better than that of the simple Kriging method in the accuracy. The spatial differentiation of the K values in this study area showed a trend of low in the north and southwest and high in the middle and southeast, and the most widely distributed soil erodibility grade is the medium erodible. 3) The altitude and land use type had a significant effect on the K values in this study area, showing the decrease trend with the increase of altitude in general, and the trend of orchard > other forest land > arbor forest land > shrub land in different land use types.

Conclusions This study can provide reference for the spatial characteristics of soil erodibility and the prediction and control of soil and water loss in the watershed and scientific guidance for managing the risk of soil erodibility in the Huangqian watershed of Shandong province.