The Variations Of Soil Respiration And Microbial Biomass Carbon At The Different Vegetation Types Of Urban Green Spaces

Urban green space is one of important components in global carbon cycling. The research on carbon cycles in urban green space has rarly been reported in china. The variations and its main influening factors of soil respiration and soil microbial biomass carbon of three typical vegetation types (lawn, open woodland, and close-to-natural forest) in Nanjing Zhongshan Botanical Garden were studied. The purpose of this study was to examine the variations of soil respiration and soil microbial biomass carbon, and to clarify the response of different urban vegetation types to regional and global climate change. Our results showed that:(1) The soil respiration rate of the three vegetation types had a significant seasonal fluctuation, was highest in summer (August) and the lowest in winter (December). For the close-to-natural forest, open woodland, and lawn, their soil respiration rate in summer was 3.28, 4.07, and 7.58μmol·m-2·s-1, and that in winter was 0.82,0.99, and 1.42μmol·m-2·s-1, respectively. The annual mean soil respiration rate differed significantly with vegetation types (P< 0.05), which was in order of close-to-natural forest< open woodland< lawn. Soil temperature was the most important regulating factor on the seasonal fluctuation of soil respiration rate. The correlation between soil moisture and soil respiration rate was not significant. The Q10 value was different in the three vegetation types, and was larger in close-to-nature forest than that in open woodland and lawn.(2) The soil respiration had significant diurnal variation in the three vegetation types, which was basically the single-peak pattern. The highest peak appeared at 14-17:00, and the lowest one appeared at 4:00-7:00. The result of the daily average rate of soil respiration was in order of lawns> open woodland> close-to-natural forest. The soil respiration of three vegetation types was mainly regulated by the temperature of soil and temperature of near-surface air. But there was not significant correlation of soil respiration and soil moisture.(3) There were significant seasonal fluctuations of soil microbial biomass carbon in the three vegetation types, which maintained at the highest level in the summer (July); but the lowest level was not obvious. The annual mean soil microbial biomass carbon differed in different vegetation types, but not significantly (P> 0.05). It was in order of close-to-natural forest< open woodland< lawn. The soil microbial biomass carbon had no significant correlation with soil temperature and soil moisture (P> 0.05). There were significant correlation of soil microbial biomass carbon and soil total organic carbon, and no significant correlation of soil microbial biomass carbon and soil total nitrogen, total sulphur, C/N ratio and pH value(P> 0.05), respectively.Our results indicate the variations of soil respiration and soil microbial biomass carbon at the different vegetation types of urban green spaces, and the rapid development of lawn might increase the CO2 emission from soil carbon pool in urban area...