Abstract
The restoration of vegetation in abandoned farmlands is an effective approach to control soil erosion on the Chinese Loess Plateau. However, few studies have investigated the effect of natural restoration age on the infiltration patterns and preferential flow in soil layers. This study examined the effect of the temporal variations in the degree of preferential flow and their contribution on the total infiltration in abandoned farmlands restored with different vegetation communities. In total, four sites were investigated, namely site AF3, AF12, AF18 and AF25 of restoration age of 3, 12, 18 and 25 years, respectively. A traditional dye tracer experiment was adopted to visualize the water flow behavior in the four sites. A semi-variance analysis was conducted to interpret the spatial variability of the soil water induced by infiltration. The results showed that both the soil properties and the root systems improved with the increased natural restoration ages combined with the effect of the plant species. The degree of preferential flow from the lowest to the highest occurred in AF3, AF12, AF18 and AF25, which was mainly affected by the development of root systems. Also, the abundant lateral root and steeper slope may have caused the presence of lateral flow in AF18 and AF25. Meanwhile, the spatial variability of the soil water in the infiltration patterns through vertical soil profiles increased from AF3 to AF25. Compared to AF3, the infiltration volume through preferential pathways in AF12, AF18 and AF25 increased by 1.73 times, 1.94 times and 4.09 times, respectively. Therefore, the preferential flow was improved in abandoned farmland in the presence of natural vegetation restoration that can increase water storage in the deep soil layer and reduce surface runoff and erosion.
Highlights
The Chinese Loess Plateau has suffered from severe soil erosion for several decades
This study quantified the temporal variations in water flow behaviour of different vegetation communities in abandoned farmlands on the Loess Plateau
The results showed that the soil organic matter content (SOM) and the water stable aggregate (>0.25 mm) content (WR0.25 ) increased with natural restoration age, while the bulk density (BD) decreased from AF3 to AF25
Summary
The Chinese Loess Plateau has suffered from severe soil erosion for several decades. The impact of human activities in the plateau can be attributed to continuous and widespread stress, such as large-scale monocultures (wheat and maize) and over-grazing [2]. To control soil erosion and ecosystem degradation, the Chinese government initiated the “Grain-for-Green” project across the country in 1998. As important management of the project, vast areas of farmland in the Loess Plateau have been abandoned and converted into grasslands, shrublands or forests with natural vegetation [3]. The soil loss of the plateau decreased by 57% and the vegetation cover increased by 13 times since 1998 [4,5]. The dense vegetation restoration activities and the increasing vegetation cover require a greater amount of
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