Abstract: Alchornea davidii is an adaptive species, playing important roles in water and soil conservation in Karst areas. To analyze the differences of population structures, dynamics and spatial patterns of A. davidii, and further to provide guidance for its better use in vegetation restoration, a comparative study was carried out under four different disturbed (mild, moderate, strong and severe) Karst environments in Chongqing. The results showed that: (1) the population age structure presented an upward pyramid type and the population size kept growing under moderate, strong and severe disturbances. (2) Population survival curve followed a stable Deevey Ⅱ curve under mild and moderate disturbances, but a Deevey Ⅲ curve with a strong population increase under strong and severe disturbances. (3) Populations under mild and moderate disturbances had higher survival rate and life expectancy, and their survival rate and cumulative mortality rate had smaller fluctuation than those under strong and severe disturbances. The populations under severe disturbance suffered a severe environmental screening from the first age class to the second age class. (4) The values of dynamic quantitative index V_pi and V′_pi increased with disturbance intensity, indicating that the populations had higher growing ability in highly disturbed environment. (5) All populations under different disturbances showed an obvious clumped distribution at five different plot sizes, and the patchiness index of populations in highly disturbed environments was lower than that in lowly disturbed environments, which suggested that the former populations were more expanding. Therefore, A. davidii is suitable for early stage vegetation restoration in Karst areas.

Key words: forest canopy cover, ICESat-GLAS, Landsat-TM, multi-source remote sensing data, BPneural network model.