Soil splash erosion: An overlooked issue for sustainable rubber plantation in the tropical region of China

Soil erosion by water is known to be a major driver of land degradation. Splash erosion is the initial stage of water erosion and directly contributes to the detachment of soil particles on sloping land. Splash erosion may be exacerbated or mitigated by ongoing land use/cover change. To estimate the effects of various land use and management systems on splash erosion in the humid tropics, we measured the actual splash erosion under natural rainfall conditions in a tropical rainforest (TR), rubber monoculture (RM), and four rubber agroforestry ecosystems in Xishuangbanna, Southwestern China. The average cumulative splash mass in the RM was 48.7 times higher compared to that in the TR, indicating that the replacement of TR by RM results in severe splash erosion. In the rubber agroforestry systems, the throughfall kinetic energy and splash mass were 34–76% and 86–97% lower, respectively, than that in the RM, indicating that intercropping crops with rubber trees can effectively alleviate erosive power of throughfall and thus splash erosion. Under all land use regimes, in the plots where the litter layer was removed, splash erosion was significantly (2.0–12.1 times) higher and more spatially heterogeneous than in those with litter cover. This highlighted the key role of the forest litter layer in protecting the soil from raindrop detachment. In the study area, the actual splash erosion was strongly correlated with the conditions of precipitation (amount and intensity (I₁₀) of rainfall) and the vegetation structure (especially the crown base height, leaf area index, and canopy cover), but weakly correlated with the soil properties. Given the importance of near-ground intercrops (height <5 m) for improving the vegetation structure, surface cover, and soil conditions, the intercropping of Camellia sinensis and Theobroma cacao with rubber trees is a promising approach for controlling splash erosion and also has benefits on the sustainable development of rubber plantation.