三峡库区小流域土地利用结构对土壤养分流失及水质影响

三峡水库生态屏障区土地利用类型及其结构快速变化,直接影响入库的土壤侵蚀、径流及土壤养分流失输出;研究土地利用结构对地表径流养分输出及地表水质影响,可为控制地表水质和水体富营养化提供基础数据。选取三峡库区低山丘陵区的秭归县兰陵溪小流域集水区,代表以林地(S1)、林地+园地(S2)、园地(S5)为主的典型土地利用结构,自动采集水样,常规监测及典型降雨径流过程连续监测,探究地表径流土壤养分氮磷浓度的动态变化过程。结果显示,雨季集水区间径流的氮素浓度存在较大差异,S5的氮磷输出浓度都显著高于S1和S2(P<0.05);集水区间径流的氮磷浓度变幅差异显著(P<0.05),氮磷输出浓度表现为S1

Effects of Land Use on Soil Nutrient Loss and Water Quality in the Three Gorges Reservoir Area of China

The rapid changes of land use type and structure in the ecological barrier area of Three Gorges Reservoir directly affects soil erosion, runoff and loss of soil nutrients to the reservoir. In this study, we explored the impact of land use structure on surface runoff, loss of nutrients and surface water quality in the Three Gorges Reservoir area, aiming to provide basic data for managing surface water quality and eutrophication. The Lanlingxi watershed in Zigui County, located in the low mountain and hilly area of lower Three Gorges Reservoir, was selected for a study case. A total of nine sampling sites were set in the study area (S1-S7 at the outlet of each tributary, S8 in the main stem of the Lanlingxi River and S9 at the outlet of the watershed). Three typical land uses, forest (S1), forest-garden (S2), and garden (S5) dominated in the study area. From March to October of 2017, water samples from the catchment area were collected by routine monitoring and by continuous monitoring at the three representative sites (S1, S2, S5) during rainfall events. Monitoring data was then used to explore the dynamics of soil nitrogen and phosphorus transport in surface runoff. In the rainy season there was a significant difference in nitrogen concentrations in the runoff from different catchment areas, and nitrogen and phosphorus concentrations in runoff from garden land (S5) was significantly higher than in runoff from forest land (S1) and forest-garden land (S2) (P<0.05). There were also significant differences in the concentration ranges of nitrogen and phosphorus in runoff among the catchment areas (P<0.05). Nutrient concentrations in the runoff from the S5 catchment area responded rapidly to rainfall. Based on the results of this study, we recommend increasing the proportion of forest land by more tightly controlling the proportion of land that is cultivated, constructing forest buffers along river banks, and intercropping tea within forested land. These measures will help optimize land use, thereby reducing concentrations of nitrogen and phosphorus in runoff, loss of soil nutrients, and inputs of nitrogen and phosphorus to rivers and Three Gorges Reservoir.