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| DOI：10.13522/j.cnki.ggps.2025067 |
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| Effects of vegetation on spatiotemporal variations in non-point source pollution of nitrogen and phosphorus and their drivers |
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HE Li, ZHANG Qiuying, LI Fadong, LIU Hongguang,
E Reaihan, LI Zhao, LENG Peifang, LI Caole
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1. College of Water Conservancy and Architectural Engineering, Shihezi University, Shihezi 832000, China;
2. Chinese Research Academy of Environmental Sciences, Beijing 100012, China;
3. Institution of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China;
4. University of Chinese Academy of Sciences, Beijing 100049, China
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| Abstract: |
| 【Objective】Non-point source pollution in agriculture is a major threat to ecological and environmental systems in Guangdong Province, with prominent nitrogen and phosphorus loads found in the western part of the province. However, our understanding of the effects of vegetation on such pollution remains elusive. This paper aims to bridge this gap.【Method】The study area is the Jianjiang River Basin in western Guangdong. Using the SWAT model, we simulated the non-point source pollution from 2000–2020, from which we analyzed the spatiotemporal distribution and potential spatial sources of sediment, nitrogen and phosphorus in the region. Redundancy analysis was used to elucidate the effects of vegetation coverage, population, primary-secondary-tertiary industries, agriculture, forestry, livestock, fishery, as well as fertilizer and pesticide usage on total nitrogen and phosphorus loads. We specifically analyzed the correlation between vegetation coverage and non-point source pollution.【Result】①The SWAT model was satisfactory in simulating runoff, sediment and nitrogen-phosphorus processes in the basin, with R2/NSE＞0.5. ②From 2000 to 2020, the average annual water yield in the basin was 653 mm, the average annual sediment yield was 12 321.4 tons, the average annual total nitrogen flux was 19 629.4 tons, and the average annual total phosphorus flux was 5 099.3 tons. ③Land use affected nitrogen and phosphorus pollution, with their influence ranked in the order of forestland (70% total, with orchards contributing 75% + heavy rainfall impact)＞cropland＞build-up areas＞grassland＞water bodies; the contribution of different land uses to non-point source pollution was ranked in the order of build-up areas＞cropland＞forestland＞grassland＞water bodies. ④The RDA analysis revealed that annual precipitation explained 61.8% and nitrogen fertilizer application explained 24.0% of the variation in the non-point source pollution of nitrogen and phosphorus in the basin . ⑤On average, vegetation coverage and nitrogen and phosphorus loads were weakly correlated, with r = -0.12; spatially, they were positively correlated in forestlands in the northeast and northwest of the basin, and negatively correlated in croplands and urban areas in the central-southwestern parts of the basin.【Conclusion】Forestland was the primary source of sediment, nitrogen and phosphorus pollution, closely followed by cropland. Increasing vegetation coverage in high-pollution areas such as the southwestern and central parts of the basin can mitigate such pollutions. A 10% increase in vegetation coverage could reduce total nitrogen emissions by 12.5%, though its impact on total phosphorus pollution is limited. These findings provide a basis for targeted prevention and control of agricultural non-point source pollution in the basin. |
| Key words: Jianjiang; SWAT; non-point source pollution; spatiotemporal distribution; vegetation coverage |
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