岩溶槽谷区坡面土壤磷素流失过程与影响因素——以中梁山龙凤槽谷试验场为例

为揭示自然降雨条件下岩溶槽谷区坡面土壤磷素流失规律，分析坡面径流和侵蚀泥沙中各形态磷素的迁移流失过程，并着重探讨降雨条件、土地利用方式因素对磷素流失的影响。在重庆市中梁山龙凤槽谷区设置耕地、林地和果园地3个标准径流小区（20 m×5 m），对坡面径流及泥沙中的磷素流失开展为期1年的监测。结果表明：（1）坡面土壤磷素流失强烈依赖于坡面产流产沙过程，槽谷区土壤磷素流失以径流流失为主，泥沙流失为辅；（2）总体来看，不同土地利用方式总磷（TP）流失总负荷表现为耕地 > 果园地 > 林地，耕地TP流失总负荷为0.17 kg/hm²，约是果园地的1.76倍和林地的4.68倍；（3）径流中磷素浓度变化受降雨强度控制，雨季初期径流中磷素流失形态以水溶性总磷（TDP）为主，其余降雨事件则以颗粒态磷（PP）为主，ρ（PP）/ρ（TP）的比例为63.92%~96.97%；（4）泥沙中磷素浓度变化受降雨强度影响较小，泥沙磷素存在富集现象，且全磷富集比（ER_STP）与雨强无明显相关关系。

Process of Soil Phosphorus Loss on a Slope of Karst Trough Valley and Influencing Factors-A Case Study of Longfeng Trough Valley Test Site in Zhongliang Mountain, Chongqing, China

In order to reveal the law of phosphorus loss on a slope of karst valley under natural rainfall conditions, the migration process of different forms of phosphorus through the two transport pathways (slope runoff and erosion sediment) was analyzed, and the influence of rainfall conditions and land use patterns on phosphorus loss was emphatically discussed. Three standard runoff plots (20 m×5 m) of cultivated land, forest land, and orchard land were set up in Longfeng trough valley to monitor the phosphorus loss for one year. The results showed that: (1) Phosphorus loss was strongly dependent on the process of runoff and sediment generation. (2) In general, the total loss of phosphorus decreased in the order: cultivated land > orchard land > forest land. The total loss of phosphorus in cultivated land was 0.17 kg/hm², which was about 1.76 times that of orchard land and 4.68 times that of forest land. (3) The change of phosphorus concentration in slope runoff was controlled by the rainfall intensity. The significant form of phosphorus loss in slope runoff was dissolved phosphorus (TDP) at the beginning of the rainy season, while in other rainfall runoff events particulate phosphorus (PP) was the primary form which accounted for 63.92%~96.97% of the total amount of phosphorus runoff loss. (4) The change of phosphorus concentration in sediment was less affected by the rainfall intensity, and the sediment had the enrichment effect of phosphorus, there was no obvious correlation between the enrichment ratio of total phosphorus (ER_STP) and rainfall intensity.