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在系统地研究了广东小良水保站的混交林，桉树林，裸地等三种生态系统类型的水文效益以后，本文着重探讨了它们的水土保持效益。结果表明裸地的降雨侵蚀率分别是桉树林的５．２倍，是混交林的２２８．１倍；径流侵蚀率裸地是桉树林的１１．３倍，是混交林的３１．９倍。从总体上来看，无论是降雨侵蚀率还是径流侵蚀率都是混交林的最小，而且从侵蚀物的组成来看，混交林地表径流中的悬浮物占较大的比重。侵蚀物与降雨量存在ｘ＝ｆ（ＰＡ）的相关关系，Ａ的大小反映了降雨对侵蚀的影响程度，不同的土壤是不同的，混交林Ａ＜１，桉树林Ａ＝１．４８，裸地Ａ＝１．８５，侵蚀率的年间变化以混交林的最大。用灰色系统的ＧＭ（２，１）模型，本文较为成功地预测了年际间的侵蚀率。
After systematically studying the hydrological benefits of three ecosystem types such as mixed forest, eucalyptus forest and bare land in Guangdong’s Xiaolan Hydropower Station, this paper focuses on the benefits of soil and water conservation. The results showed that the erosion rate of bare land was 5.2 times that of eucalyptus forest and 228.1 times that of mixed forest respectively. The erosion rate of bare land was 11.3 times that of eucalyptus forest and 31.9 times that of mixed forest. Generally speaking, both the rainfall erosion rate and the runoff erosion rate are the minimum in the mixed forest, and from the composition of the erosion, the suspended sediment in the mixed forest surface runoff accounts for a large proportion. The relationship between erosion and rainfall is x = f (PA). The size of A reflects the degree of rainfall on erosion. The different soils are different, with A <1, Eucalyptus forest = 1.48, bare A = 1.85, the annual change of erosion rate is the largest in mixed forest. With the GM (2,1) model of gray system, the paper predicts the erosion rate more interannually.