Abstract: Abstract Nitrogen fixing and non-nitrogen-fixing species of north deciduous trees were studied to characterize the variation of nutrient contents and its seasonal dynamics. The results showed that the content of Nand Mg in foliage was significantly different between nitrogen-fixing and non-nitrogen-fixing trees during fast growing to leaf fallen period. The reduction tendency of Nand Kcontents in N-fixing trees was much slower than that of non N-fixing trees, but the accumulation of other elements and ash was higher than that in non N-fixing trees. Based on F-test and T-test, elements N, P, Mg and Si were selected as variables for numerical classification, and N-fixing and non N-fixing tree species were divided successfully.

Key words: Deciduous trees, Nitrogen-fixing tree species, Nutrient content, Numerical classification, zoobenthos, habitat value, Yangtze River estuary, Phragmites australis, dominant species