National scale assessment of the soil erosion and conservation function of terraces in China

Terraces are not only productive but also have outstanding ecological functions, becoming an important soil and water conservation measure worldwide. Although there are many studies on soil and water conservation in terraces, due to the lack of data on the spatial distribution of terraces, most of the current studies are focused on small areas, lacking large-scale studies. This study is the first to quantitatively measure soil erosion and soil and water conservation capacity of terraces and their spatial distribution throughout China. The spatialization method and Revised Universal Soil Loss Equation model were used to calculate the soil erosion modulus and quantity of terraces and slope farmland at the pixel scale. The results showed that the average soil erosion modulus and soil erosion quantity for the terraces in China in 2017 were 273.56 t km-2 a-1 and 4.88 x 107 t, respectively. The average soil conservation modulus and soil conservation quantities in 2017 were 2132.59 t km-2 a-1 and 3.81 x 108 t, respectively. The terraces maintained 88.63% of the soil from erosion at the national scale. The vast majority of terraces experienced micro erosion (84.53%) and slight erosion (14.97%), with only a small percentage area of terraces experiencing moderate erosion and above. Spatially, the terraces in the Black Soil Area, Red Soil Area, and Rocky Mountain Area had better soil conservation effects, while the terraces in the Loess Plateau and Tibetan Plateau had poor soil conservation effects. Findings from this study will help to understand regional differences in soil erosion in terraces in China, which in turn will help to formulate environmental protection policies.

Automated summary

Terraces are not only productive but also have important water and soil conservation functions. This study quantitatively measured soil erosion and conservation capacity of terraces nationwide in China for the first time. Results showed that terraces maintained most of the soil from erosion at the national scale, with different regions showing varying degrees of soil conservation effects.