Three Gorges reservoir area Organic matter content of the bare lateritic surface-layer in east Yunnan karst rocky deserts

The bare laterite is a special desert landscape discovered in east Yunnan in the recent years. In order to understand the reason for the exposure of the laterite, the organic matter contents in the samples from laterites with and without vegetation cover are analyzed. The samples are collected in typical karst rocky deserts in Fuyuan, Xuanwei, Luoping counties. It turns out that the organic matter content of the bare lateritic surface-layer, averaging in 1.31%, is among 0.06%~3.85%. This value is lower than that with vegetation cover in the same area and that of other kind of soil samples in southwest China karst region. In the process of rocky desertification, there is large amount of loss in the organic matter from the soil because of the vegetation deterioration. Correspondingly, the soil structure and the preserving ability of moisture and fertility are affected, which brings the exposure of the late rite. Patches of bare laterite may represent a transition stage in rocky desertification. In this stage, there is vegetation degradation and the soil hasn’t been completely eroded yet.