Abstract: To clarify the relations of landslide and debris flow hazards to envir onmental factors is of significance to the prediction and evaluation of landslid e and debris flow hazards. Base on the latitudinal and longitudinal information of 18431 landslide and debris flow hazards in China, and the 1 km×1 km grid dat a of elevation, elevation difference, slope, slope aspect, vegetation type, and vegetation coverage, this paper analyzed the relations of landslide and debris f low hazards in this country to above-mentioned environmental factors by the ana lysis method of frequency ratio. The results showed that the landslide and debri s flow hazards in China more occurred in lower elevation areas of the first and second transitional zones. When the elevation difference within a 1 km×1 km gri d cell was about 300 m and the slope was around 30 degree, there was the greates t possibility of the occurrence of landslide and debris hazards. Mountain forest land and slope cropland were the two land types the hazards most easily occurre d. The occurrence frequency of the hazards was the highest when the vegetation c overage was about 80%〖KG-*2〗-〖KG-*7〗90%.

Key words: light regime, photosynthetic characteristics, phenotypic plasticity, biomass, Alnus formosana, Alnus cremastogyne.