Abstract: By using Li6400 portable photosynthetic apparatus connected to soil chamber, the soil respiration rate under three vegetation types (lawn, open woodland, and closetonature forest) in Nanjing Zhongshan Botanical Garden was measured from October 2007 to September 2008, with related affecting factors analyzed. The soil respiration rate had obvious seasonal fluctuation, being the highest in summer (August) and the lowest in winter (December). For the closetonature forest, open woodland, and lawn, their soil respiration rate in summer was 3.28, 4.07, and 7.58 μmol·m^-2·s^-1, and that in winter was 0.82, 0.99, and 1.42 μmol·m^-2·s^-1, respectively. The annual mean soil respiration rate differed significantly with vegetation type (P<0.05), which was in  order of close-to-nature forest<open woodland<lawn. The soil respiration rate had significant exponential correlation with soil temperature, but no correlation with soil moisture.  The Q_¹⁰ value increased with increasing soil depth, and was larger in close-to-nature forest than in open woodland and lawn. Our results indicated that the rapid development of lawn in urban green space could increase the urban soil CO₂ emission.

Key words: Crop yield, Soil fertility, Nutrient balance, Long-term fertilization, Upland red soil