Keywords: 
• soil science /
• urban green-belt /
• soil respiration /
• plant communities /
• soil temperature /
• soil water content /
• labile organic carbon /
• CO2

Abstract: The soil respiration rate of nine plant communities （Cinnamomum camphora，Torreya grandis-Ginkgo biloba，Cedrus deodara，Ginkgo biboba，Osmanthus fragrans，Cercis sp.，Lolium perenne-Cynodon dactylon，Zoysia japonica，and Cynodon dactylon） in Shanghai City were studied with a CFX-2 Soil Respiration Chamber，and the main influential factors were identified，and the aim was to evaluate correctly soil respiration of urban soil. The digital thermometer was used to test the air temperature，the soil temperature at 5 cm depth and the soil temperature at 10 cm depth. And all data were average of three replications，and a correlation analysis was also employed. Results showed that soil respiration rates varied by season with the maximum found from June to September and the minimum from December to the following March. Daily variation in the soil respiration rate under communities of trees and bushes was generally stable; whereas a lawn had a single-peaked curve. The maximum soil respiration rates （5.51 molm－2s－1） found under Cynodon dactylon and the minimum （2.76 times less） found under a Cercis sp. community. The soil respiration rate had a significant exponential correlation （P＜0.01） with the air temperature，the soil temperature at 5 cm depth，and the soil temperature at 10 cm depth. Soil water content had an effect on soil respiration under lawns，but it had a relatively small influence on tree and bush communities. The soil labile organic carbon content was ranked in the following order: light fraction organic carbon （LFOC） ＞ microbial biomass carbon （MBC） ＞ dissolved organic carbon （DOC），but MBC and DOC had the greatest influence on the soil respiration rate. The maximum released quantity of CO2 reached to 33.18 thm－2a－1 under lawns, which was 1.95 times that of trees and 2.12 times that of bushes.［Ch，3 fig. 6 tab. 30 ref］