Changes in Soil Physicochemical Properties By Landslide Deposition in Xitou, Central Taiwan.

The steep mountain terrain, fractured geological structure, and intense precipitation events are primary factors contributing to frequent landslides in the mountainous regions in Taiwan. The impacts of landslide on forest can be immense and create spatial heterogeneity of soil properties that require to be known for the subsequent forest revegetation and management. In this study, the effects of landslide deposition on soil physiochemical properties were investigated from a sedimentary rock in a moist montane forest ecosystem in Xitou, central Taiwan. We established (1) a data set that compared the differences in soil properties between 1977 survey and current soil survey data for soil samples undergone with and without the occurrence of landslides, and (2) a series of sampling sites with varying degrees of landslide effects. The results indicated that soil pH, bulk density, inorganic carbon, and base saturation increased following landslide deposition and that the greater severity of the landslide was the greater these increases were. By contrast, the thickness of O and A horizon, soil organic carbon, total nitrogen, and cation-exchange capacity significantly decreased following a landslide, and the level of decrease declined as the extent of the landslide declined. The exchangeable potassium, calcium, magnesium, and available phosphorus contents were unaffected by landslide deposition. These results demonstrate that landslide deposition plays an important role in affecting soil physiochemical properties and these changes in soil properties are expected to influence the functions of forest ecosystems.