Abstract:

Response of dominant tree seedlings from secondary successional forests to gradients of pH value,moisture,nutrients and light was studied in order to further test the adaptability of dominant tree seedlings to the environment in the south subtropical zone,Guangdong Province,China.These species were Pinus massoniana (pioneer species),Schima superba and Castanopsis fissa (transitional species),Cryptocarya concinna (late-successional species).The techniques to determine the response of these species seedlings to the gradients of the environment were ecophysiological technique by combining niche breadth,niche overlap and deviation from the central value of the niche.The data were the rate of net photosynthesis and the export and distribution of photosynthetic product determined by ¹⁴C-glucose treatment.The pioneer seedlings exhibited the highest rate of net photosynthesis and export and distribution of photosynthetic product to growth bud in the high light,also exhibited the largest niche breadth and deviation value at the soil moisture gradient,the late successional species seedlings was contrary.These values in the pioneer seedlings decreased when seedlings were transferred to low light condition for l year,and the seedlings of both transitional and late-successional species had the highest rate of these in the forest gap habitats,no in some shade habitats. Because of the development of root system,the transitional tree seedlings showed the largest niche breadth and deviation value at the nutrient and pH value gradient,and pioneer seedlings were contrary at nutrient gradient,late-successional seedlings were contrary.Finally,the value of the niche overlap of these seedlings showed that strong competition among tree species in the successional forest communities.

Key words: Niche, Dominant tree species of community, Ecology adaptation, Secondary forest succession