Soil and nutrient loss play a vital role in eutrophication of water bodies. Several simulated rainfall experiments have been conducted to investigate the effects of a single controlling factor on soil and nutrient loss. However, the role of precipitation and vegetation coverage in quantifying soil and nutrient loss is still unclear. We monitored runoff, soil loss, and soil nutrient loss under natural rainfall conditions from 2004 to 2015 for 50–100 m2 runoff plots around Beijing. Results showed that soil erosion was significantly reduced when vegetation coverage reached 20% and 60%. At levels below 30%, nutrient loss did not differ among different vegetation cover levels. Minimum soil N and P losses were observed at cover levels above 60%. Irrespective of the management measure, soil nutrient losses were higher at high‐intensity rainfall (Imax30>15 mm/h) events compared to low‐intensity events (p < 0.05). We applied structural equation modelling (SEM) to systematically analyze the relative effects of rainfall characteristics and environmental factors on runoff, soil loss, and soil nutrient loss. At high‐intensity rainfall events, neither vegetation cover nor antecedent soil moisture content (ASMC) affected runoff and soil loss. After log‐transformation, soil nutrient loss was significantly linearly correlated with runoff and soil loss (p < 0.01). In addition, we identified the direct and indirect relationships among the influencing factors of soil nutrient loss on runoff plots and constructed a structural diagram of these relationships. The factors positively impacting soil nutrient loss were runoff (44%–48%), maximum rainfall intensity over a 30‐min period (18%–29%), rainfall depth (20%–27%), and soil loss (10%–14%). Studying the effects of rainfall and vegetation coverage factors on runoff, soil loss, and nutrient loss can improve our understanding of the underlying mechanism of slope non‐point source pollution.
Runoff and soil erosion on sloping farmland pose a serious threat to agricultural productivity. Soil and water conservation management is considered to be effective in controlling runoff and soil erosion, especially in sloped farmland. In this study, 1910 natural rainfall events were monitored to evaluate the effectiveness of soil and water conservation management and rainfall types on runoff and soil erosion. The results confirmed that fish‐scale pit plots reduced runoff and soil loss by 70.18 and 91.07%. Runoff and soil loss on sloped farmland and naturally sloped plots were significantly higher (p < .05) than the other four soil management interventions. “Intense” events were the main causes of runoff and soil loss production, but the influence of “intense” rainfall events on runoff and soil loss was weakened by narrow terraced farmland. About 10% of the largest rainfall events represented from 21 to 27% of the rainfall depth, from 35 to 54% of the total runoff, and from 71 to 88% of the total soil loss. Rainfall intensity plays a dominant role in soil erosion, while rainfall accumulation is the main influencing factor for runoff. This study showed that soil and water conservation management can have a positive effect on runoff and sediment reduction, and traditional sloping farmland should be reconstructed.
High nitrogen (N) and phosphorus (P) levels are the main causes of eutrophication of water bodies, and the chemical oxygen demand (COD) is one of the indices of relative organic matter content. Several simulated rainfall experiments have been conducted to investigate the effects of a single controlling factor on soil and nutrient loss. However, the role of precipitation and vegetation coverage in quantifying soil and nutrient loss is still unclear. We monitored runoff, soil loss, and soil nutrient loss under natural rainfall conditions from 2004 to 2015 in runoff plots around Beijing. Soil erosion was significantly reduced when vegetation coverage reached 20 and 60%. At levels below 30%, nutrient loss did not differ among different vegetation cover levels. Minimum soil N and P losses were observed at cover levels above 60%. Irrespective of the management measure, soil nutrient losses were higher at high-intensity rainfall events compared to low-intensity events (p < 0.05). We applied structural equation modelling (SEM) to systematically analyze the relative effects of rainfall characteristics and environmental factors on runoff, soil loss, and soil nutrient loss. At high-intensity rainfall events, neither vegetation cover nor antecedent soil moisture content (ASMC) affected runoff and soil loss. After log-transformation, soil nutrient loss was significantly linearly correlated with runoff and soil loss (p < 0.01). In addition, we identified the direct and indirect relationships among the influencing factors of soil nutrient loss on runoff plots and constructed a structural diagram of these relationships. The factors positively impacting soil nutrient loss were runoff (44-48%), maximum rainfall intensity over a 30-min period (18-29%), rainfall depth (20-27%), and soil loss (10-14%). Studying the effects of rainfall and vegetation coverage factors on runoff, soil loss, and nutrient loss can improve our understanding of the underlying mechanism of slope non-point source pollution.
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