| Urban green space was praised as "Lung of City", and the effect and function of it were much accounted of urban governor and designer all the time. Currently, at local and abroad, relevant research have confirmed that urban green space play an important portion in regulating air temperature and relative humidity, photosynthetic carbon fixation, releasing oxygen and generating nagitive air ions (NAI),especially spatial designs based on natural forests (e.g.,the incorporation of natural floristic composition, type and structure of plant community).Beijing Olympic Forest Park (BOFP) is a great urban green space, which was build by natural forestry ecolosystem, and it is located north of the main Olympic stadiums (the Bird's Nest and the Water Cube) and it is a precious'green heritage'for urban dwellers. Here, we established 19 sampling points, including 17 inside the park and 2 outside the park as the urban background level, the concentration of airborne fungus, carbon dioxide and Negative air ions were measured in clear and windless days for 5 years, from 2005 to 2010. Based on these data, we discussed the daily, seasonal and annual variation of those effects. In addition, we discussed the correlation between those effects and the type and structure of plant community (PC).1.This paper investigated carbon dioxide (CO2) concentration in the Beijing Olympic Forest Park. And the results indicated that:1) In growing season, the daily average of CO2 concentration was 328μmol·mol-1,the diurnal variation of CO2 in this park was significant, presenting generally a picture of decreasing from 08:00—11:00, then fluctuating at noon (11:00-13:00) around a low concentration point (approx.310μmol·mol-1),13:00-17:00, CO2 reaching the minimum concentration (approx.300μmol·mol-1) at 14:00 pm, and increasing significantly afterwards; 2) In non-growing season, the daily average of CO2 concentration was 413μmol·mol-1, and it was higher than that in growing season. The variation characteristics of CO2 were similar to that in growing season, except for the time of the minimum concentration (13:00 pm); 3) the lowest concentration of CO2 was (328μmol·mol-1 in the summer and the highest one in the winter (413μmol·mol-1) of four seasons, but no significant difference of concentration was between the spring (410μmol·mol-1) and the autumn (413μmol·mol-1).Seasonal and annual data of CO2 concentration from 2005 to 2010 were presented in this paper, to research the vegetation ecological benefits of BOFP. The results indicated that:4) The CO2 concentration of Spring increased gradually about 33μmol·mol-1 through the measurement time (six years);in Summer, CO2 concentration dropped gradually about 30μmol·mol-1 in this period;CO2 concentration of Autumn was not significantly at present; CO2 concentration of Winter was the highest one of four seasons, and it fluctuated around high concentration in six years.5) Before this park was constructed (before 2008), CO2 concentration of this park was higer than that of urban background level, and after this park was constructed, CO2 concentration of this park was lower than that of urban background level.2.There are significant differences of CO2 concentration among those zones with different structure and type of PC.1) In BOFP, CO2 concentration in growing season followed a gradient change, decreasing gradually from near the border of the park (360μmol·mol-1) to the buffer area (336μmol·mol-1) and to the center of the park (332μmol·mol-1).2) CO2 concentration of the zones with different PS from high to low was as follow:MPC, DPC, SPC;CO2 concentration of the zones with different DPC from high to low was as follow:TG, TS, SG; and that of different SPC as follow:T, G, S. 3) CO2 concentration of the zone with different PT from high to low was as follow:G, S, CP, DBP, CBP.3.Negative air ions (NAI) concentration of BOFP has significant daily, seasonal and annual variation.1) 08:00-17:00, NAI showed significant daily variation with double peak, the first peak showed in 10:00-11:00, and the second one showed in 16:00.2) NAI of Summer was highest one in four seasons, with 2745 n·cm-3 in measurement time, and that of Spring was the lowest one in four seasons with 995 n·cm-3, and that of Autumn (2258 n·cm-3) was lower than that of Summer and higher than that of Winter (1078 n·cm-3).3) NAI of 2008(2710 n·cm-3) was the highest one through the period from 2005 to 2010,2005-2007, the trend of NAI was not significant, and 2008-2010, NAI decreased processly.4.There were significant differences of NAI concentration among different zones with different structure and type of PC, between BOFP and urban background level.1) Before 2008, NAI of BOFP was lower than that of urban background level, and after 2008, NAI of BOFP was higher than that of urban background level.2) NAI of zones with different PS from high to low was as follow:DPC, MPC, SPC;NAI of zones with different DPC from high to low was as follow:TG, SG, TS; and that of different SPC as follow:G, T.3) NAI of zones with different PT from low to high was as follow:DBP, G, S, CBP, CP.5.In BOFP, the concentration of airborne bacteria and airborne fungi has significant daily, seasonal and annual variation.1) In growing season, the daily average of airborne fungi was 176 CPU·m-3. 08:00-14:00, concentration of airborne fungi decreased significantly,14:00-17:00, it increased significantly; and the daily average of airborne bacteria was 96 CPU·m-3,08:00-14:00, the concentration of airborne bacteria showed decrease trend, and 14:00-17:00, it showed increase trend.2) In non-growing season, the daily average of airborne fungi was 111 CPU·m-3 and the value were lower than that in growing season, the time of the daily lowest concentration of airborne fungi was similar to that in growing season; concentration of airborne bacteria was 137 CPU·m-3, which was higher than that in growing season.3) Concentration of airborne bacteria of Summer was the highest one in four seasons, and that of Spring was the lowest one,114 CPU·m-3 and 66 CPU·m-3, respectly, at the same time, that of autumn and winter was similar,87 CPU·m-3 and 90 CPU·m-3, respectly; concentration of airborne bacteria in summer was the lowest one in four seasons, and that of winter followed, and it showed the characteristics of increased processly.6. There were significant differences of airborne bacteria and airborne fungi concentration among different zones with different structure and type of PC, between BOFP and urban background level.1) The airborne fungi concentration of zones with different Ps from high to low was as follow:MPC, DPC, SPC; The airborne fungi concentration of the zones with different DPC from high to low was as follow: SG, TG, TS; and that of different SPC was as follow:G, S, T; The airborne bacteria concentration of zones with different Ps from high to low was as follow:SPC, DPC, MPC; The airborne bacteria concentration of zones with different DPC from high to low was as follow:SG, TG, TS; and that of different SPC was as follow:G, S, T.2) The airborne fungi concentration of zones wth different PT from low to high was as follow:DBP, G, S, CBP, CP; The airborne bacteria concentration of zones with different PT from low to high was as follow:G, S, DBP, CBP, CP.Moreover, the comparative study between BOFP and other urban green space (Haidian Park) clarified the factor of green spaces, such as area, shape, the strcture and type of plant community, which affect the ecological effects of green spaces. Due to the effects of green vegetation, the ecological factor of urban green space had significant daily, seasonal and annual variation, and the environmental quality of urban green space was better than that of urban generally environment (urban background level).In the zone of urban green space, different Ps and PT had different effect to the ecological effects. And these results would benefit to the construction of plant landscape and government of urban green space. |
