Abstract: Based on the RS image digitization, investigations on representative communities, measurement of dominant species physiological variables, and CITYgreen model, this paper evaluated the carbon fixation of urban forests in Shanghai, and studied the effects of community structure on the carbon fixation of the forests. The total carbon storage and the annual carbon sequestration of urban forests in Shanghai were 478472 t and 6256 t, and the average carbon density and av
erage carbon sequestration rate were 47.80 t·hm^-2 and 0.625 t·hm^-2·a^-1, respectively. The carbon sequestration rate was significantly positively correlated with canopy closure and community density but negatively correlated with average DBH, and the carbon density was significantly positively correlated with canopy closure and average DBH but had no significant correlation with community density. The forests with low density and high DBH had higher carbon density than those with medium or high density. Mixed forests had higher carbon density than pure forests, multilayer forests had higher carbon density and c
arbon sequestration rate than monolayer forest, and the differences were to some extent affected by average DBH and community density.

Key words: Soil, Microbial diversity, Biolog, FLFA, Nucleic acid-based analysis