Forestation does not necessarily reduce soil erosion in a karst watershed in southwestern China

Abstract

Forestation as part of the Returning Farmland to Forest Project was implemented to mitigate soil erosion in southwestern China. However, whether forestation has effectively reduced soil erosion in southwestern China remains unclear, mostly because of the lack of monitoring forest cover change and soil erosion at watershed scales. We interpreted forest cover change from satellite images and simulated soil erosion changes for the period of 1986–2018 in the Chong’an River Basin with the Water and Tillage Erosion Model and Sediment Delivery Model. Our results show that the change in forest cover has the highest correlation coefficient with the sediment yield in the watershed, with an obvious inverse phase relationship between them for all the simulated years. From 2002 to 2014, large-scale forestation and frequent droughts caused the forest cover to vary, resulting in significant changes in the annual soil erosion amount. Because crevices favoring tree growth are more developed in limestone than in dolomite, the forest cover reduction on dolomite is significantly higher than that on limestone under severe droughts in karst areas. Our study implied that the function of forestation in preventing soil erosion depends on lithology in karst areas.

Central European forest–steppe: An ecosystem shaped by climate, topography and disturbances

“…As noted above, the combination of low water‐holding capacity (e.g. on dolomitic soils) and high erosion rates on steep slopes may result in suppression of forest succession even under a moderately humid macroclimate (Feng et al, 2020; Zólyomi, 1953).…”

Lithology‐mediated soil erodibility characteristics after vegetation restoration in the karst region of Southwest China

“…Because of the connection of underground cracks in karst areas, water and soil can easily reach out, resulting in a lack of water for plants (Liu et al, 2021). At the same time, there were more cracks in the limestone areas than in the dolomite areas (Feng et al, 2021). This phenomenon makes limestone areas more prone to water scarcity by plants, which exacerbates soil erosion in limestone areas (Liu et al, 2019).…”

Jennings’ Karst (1971, MIT Press) and current critical zone science

“…For example, the importance of rock in the composition and dynamics of karst vegetation has been clarified (Liu et al, 2019; Zhu et al, 2021), and the classic climate–vegetation relationships have been updated. Furthermore, it has been proved that vegetation restoration activities do not necessarily reduce soil erosion in karst regions because climatic drought events threaten the sustainability of planting and its ability to conserve soil (Feng et al, 2021). Crop yield from an upper slope position would be greatly reduced by soil erosion (Liang et al, 2021), and this type of area may be one where forest planting activities such as those carried out by the Grain for Green project should first be applied.…”