| Urban vegetation has been one of an important index for measuring the ability of civilization progress and sustainable development. Following the process of urbanization, urban environmental problems such as air pollution, heat-island effects, and water loss have become increasingly prominent, so the research about ecological service function of urban vegetation was urgent. And the microclimate character of urban vegetation shows an important part of the indirect ecological service function—ecological benefit. Nowadays the microclimate research about artificial vegetation was general, but that of semi-natural vegetation (secondary vegetation) in urban area was very little.In this paper, we did research on typical plant community of semi-natural vegetation(deciduous broad-leaved forest) in New Jiangwan Town(former Jiangwan airport) Shanghai, which is formed as semi-natural vegetation under less artificial disturbance in urban area. On the base of comprehensively community survey, we choose typical plant community as under canopy microclimate Monitoring site in New Jiangwan Town, and also the nearby barren land as open space microclimate monitoring site. At same time, the microclimate monitoring sites in Xujiahui, Shanghai botanical Garden and Chenshan was chose as contrast. Through comparative analysis of different monitoring sites, some results are given as follows:(1) From 2006.08 to 2007.03, there was no significant difference between monthly mean values of under canopy air temperature and that of open space, and only in summer the monthly mean values of open space air temperature was higher than that of under canopy. But there was significant difference between the monthly extreme air temperatures of under canopy and that of open space, namely the monthly highest air temperature of open space was higher than that of under canopy site, and the monthly lowest air temperature of open space site was lower than that of under canopy site. Above-mentioned conclusion also proved that the deciduous broad - leaved forest has the ability of alleviating the amplitude of air temperature variation.The daily air temperature range and monthly air temperature range of Xujiahui site was significant higher than that of New Jiangwan Town, and the air temperature alleviation effect of semi-natural vegetation in New Jiangwan Town was stronger in summer and autumn than it was in winter and spring. Also during the monitoring period, the diurnal air temperature of under canopy was higher than that of open space, but there was no significant difference between the nightly air temperatures of two sites.From 2006.08 to 2007.03, the air relative humidity of under canopy was significant higher than that of open space, and this difference was more obvious in autumn comparing with summer. There was no significant difference between the extreme air relative humidity of open space and that of under canopy. The daily air relative humidity range of Xujiahui site was significant higher than New Jiangwan town in summer, but it was contrary in autumn. Above-mentioned conclusion proved that the semi-natural vegetation has the ability of alleviating the amplitude of air relative humidity variation, but its seasonal variation was get along with the variation of plant transpiration in different seasons.On rainy and cloudy days, the air temperature daily course of New Jiangwan Town sites shows the upside down U shaped. In the daytime the air temperature of open space was higher than that of under canopy, but there is no significant difference in the nighttime. On the sunny days, the air temperature daily course also shows the upside down U shaped, but the air temperature of open space significant higher than that of under canopy on the whole day.The air relative humidity daily course of New Jiangwan Town sites shows the U shaped. And on rainy and cloudy days, there was no significant difference between the nightly air relative humidity of two sites. But the diurnal air relative humidity of under canopy was slightly higher than that of open space. On sunny days, the daily air relative humidity of open space was slightly lower than that of under canopy. The daily peak value of air relative humidity appeared around the sunrise time, and the daily valley value appeared around 12:00.(2) In winter and autumn, there was no significant difference between the air temperature of New Jiangwan Town and that of Shanghai Botanical Garden, but they were slightly higher than that of Chenshan. And in autumn the daily air temperature range decreases gradually from city center to suburb and exurb, but the air relative humidity and the daily range increases gradually from center to suburb and exurb. In autumn there was no significant difference among the three sites.(3) Except 2006.08, there was significant linear relationship between the air temperature of under canopy and that of open space during the other months, and so as the air relative humidity. And the slope of the linear functions represents the seasonal change of the relative degree.(4) From 2006.08 to 2007.03, the monthly mean 0-10cm soil temperature, 10-20cm soil temperature of open space was higher than that of under canopy in summer and spring, but there was no significant difference in autumn and winter. And during the same period, there was no significant difference between the monthly mean air temperature of open space and that of under canopy. So the difference of soil temperature was caused by the difference of solar radiation. Because of the different soil pore structure of the different soil layer, the soil temperature of upper layer was higher than the under layer in under canopy site, but there was no significant difference between the upper and under soil layer in open space site.The soil temperature daily course was different in different weather condition. The soil temperature daily course of New Jiangwan Town sites shows the U shaped that was the same as air temperature daily course, but the daily peak value of the soil temperature lag behind the daily peak value of the air temperature. The daily soil temperature range on sunny days was higher than it was on cloudy days, but the daily range was greatly decreased on rainy days and no obviously peak value appeared.(5) In summer and spring, the soil temperature of Xujiahui was significant higher than that of New Jiangwan Town, but it is contrary in autumn and winter. These results were caused by different thermal capacity and heat conduction property of the land surface in different microclimate monitoring sites, also shows the soil cooling effect of the semi-natural vegetation in summer and spring and the soil warming effect in autumn and winter.(6) From 2006.08 to 2007.03, the soil water content of open space was higher than that of under canopy, and also the monthly soil water content range was lower in the under canopy site.(7) Because of the close canopy of the typical community, the semi-natural vegetation has the significant effect on decreasing the GSR, PAR and UVB radiation in summer, and henceforth the radiation sharply decreased in open space site, but there was no significant decreased in under canopy site. Above-mentioned results were because of that during the defoliation period of canopy plant in autumn and winter. Although it was during the leaf-expansion period in spring, the crown density was also at a lower level, so the radiation of under canopy site has significant increased in spring.(8) The solar radiation daily course was different in different weather condition. On sunny days, there was significant difference between the open space canopy site and the under canopy site. And this difference would be reduced when the sunshine time decreased, and there were several peak values in its upside down U shaped daily course. And on the rainy days (sunshine time greatly low),the solar radiation of open space lightly higher than that of under canopy, and the daily course of two sites also shows the upside down U shaped. But comparing with the sunny days this difference appeared at a shorter time range, always at 12:00-18:00.(9) The UVB radiation of open space was higher than that of under canopy. There was both herb community in the under canopy site and open space site, so there was no significant difference between the UVB reflective radiation of under canopy site and that of open space site. But the UVB reflective radiation of the two sites was significant lower than the concrete surface. So this result proved that vegetational cover reduces the surface reflective rate for solar radiation.(10) There was typical power function relation between GSR and PAR in the open space site, and there was typical Quadratic function relation between GSR and PAR in the under canopy site.(ll)The human comfort index was highest at New Jiangwan Town under canopy monitoring site, and was lowest at Xujiahui site in all four seasons. And this difference was most obviously in summer (August), and was least obviously in winter (January).The human comfort index of vegetation area was significant higher than that of central urban district. The human comfort index of New Jiangwan Town under canopy monitoring site was higher than that of nearby open space monitoring site, and also higher than that of green land in same urban area, and this difference was more obviously in summer and autumn.Therefore, this thesis concluded the yearly , monthly and daily course of microclimate character of semi-natural vegetation in New Jinagwan Town and which supplies a gap of research on semi-natural vegetation, and provided the long-term fundamental data for urban vegetation ecosystem research.
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