| Summary: | 碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 105 === Landslides may exert immense impacts on soil properties, nutrient speciation and forest ecosystems. The impacts of landslides on soil properties not only vary with their movement type (deposition or removal) or scale but also the succeeding vegetation can have great contribution to spatial variation inside landslide. In this study, the effects of movement type (deposition or removal) and succeeding vegetation on soil properties and nutrient speciation inside the Chiufenershan landslide scar were evaluated. Landslide soil was also compared with the adjacent undisturbed soil. According to the movement type and vegetation, we divided soil samples into three main sites (removal, deposition and undisturbed sites). And then divided soil samples into six small sites, including (i) removal site without vegetation, REM-NG (ii) removal site with vegetation, REM-G1 (iii) removal site at a gentle slope with vegetation, REM-G2 (iv) deposition site with secondary forest, DEP-SEC (v) deposition site with plantation forest, DEP-PLA and (vi) Adjacent undisturbed sites, UND.
Our results indicated that soil properties and nutrient at removal sites (REM-NG, REM-G1 and REM-G2) had higher bulk density, rock fragment content and pH value, but less soil organic carbon, total nitrogen, CEC and N-mineralization rate than both deposition (DEP-SEC and DEP-PLA) and undisturbed (UND) sites. The soil properties without vegetation (REM-NG) even showed the extreme end compared to the soils with grass vegetation. The removal and deposition sites had similar total phosphorus concentrations, but were significantly less than that at the undisturbed sites (p < 0.05). Most of the phosphorous were HCl-P in the removal sites, Residual-P and NaOH-P in the deposition sites. Although the main phosphorus speciation in the removal and deposition sites were biologically unavailable, our results did not showed that P was the limiting nutrient for soil. However, applying both N and P could improve seedling growth. In addition, the long-term field monitoring data of soil water potential showed the deposition site (DEP-SEC) and the lower removal site (REM-G2) had water potential maintained above -1.5 MPa throughout the whole year. While the removal site without vegetation (REM-NG) and removal site with vegetation (REM-G1) had soil water potential lower than -1.5 MPa in winter, indicating that the adverse effects for both sites. Overall, the soil in removal sites without vegetation (REM-NG) showed its early stage of succession, and the soil weathering was less severe than removal sites with vegetation (REM-G1 and REM-G2). By contrast, the deposition sites had more advanced soil weathering, but the soil properties and nutrient speciation were still different from the undisturbed sites. Therefore, the Chiufenershan landslide has changed the soil properties and nutrient speciation, and it is speculated that these changes played important roles on soil and ecosystem development.
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