Patterns of runoff and erosion on bare slopes in different climate zones

Abstract

Soil erosion by rainfall and runoff is a land surface process strongly controlled by climate and is one of the most threatening environmental problems in the world. Understanding erosion processes in different climates is exceptionally important but remains unclear. A wide range of climatic gradients in China provides an ideal opportunity to investigate the effects of climate on water erosion. In this study, we selected 8 bare plots orthogonally distributed in eastern China and obtained 40 plot-years of data from 424 natural rainstorms. Then, quality-controlled data were standardized to achieve effective comparisons among different climate types. We analyzed the rainfall erosivity (R), surface runoff (r), and soil loss (A) in different climate zones with a thermal gradient of Cold-Warm-Hot and a precipitation gradient of Continental-Oceanic. Our results indicate that climatic factors have complex leverage over water erosion in multiple pathways. (1) Basic rainfall characteristics increase with increasing climatic gradients of temperature and precipitation, as does the frequency of extreme events. The yields of resultants r and A are accordingly higher in the Oceanic than in the Continental zone, yet they discordantly increase in the order of Warm-Hot-Cold. Annual maximum storms in the Continental and Warm zones have more control over the annual values of R, r, and A. The R-r-A relationships are more sensitive in the Continental or Cold zones than in other zones. (2) The potential risks of surface movements differ significantly across climatic gradients. The potentialities of r and A generally increase along increasing precipitation gradients from Continental to Oceanic and increase in the temperature order of Warm-Hot-Cold. (3) The interactions between rainfall and soil exhibit different Continental and Oceanic patterns due to climate-induced differences in rainfall patterns and soil conditions. In the case of an extreme rainstorm, rill erosion is expected to occur more readily in the Cold and Continental areas. (4) Different climatic elements play various roles in the generation of runoff and erosion. Precipitation controls the magnitude of annual yield, while temperature dominates the potential risk. These results provide robust evidence that patterns of rainfall, runoff, erosion, and their relationships are not consistent among different climate zones. This study offers systematic insight into how climate drives surface processes on hillslopes. This work can serve as a reference for the improvement of land surface models for global applicability and climate change, as well as for the standardization approach to plot data in comparative analyses.