城市森林群落结构特征的降温效应

通过野外样方实测,研究长春城市森林群落结构特征对城市森林降温作用的影响.结果表明:不同郁闭度等级城市森林温度随时间呈现相同的波动上升趋势;群落郁闭度越高,城市森林温度越低;城市森林群落结构特征影响城市森林降温效应的大小,其中,郁闭度、叶面积指数、树高对降温效应的影响最显著,而胸径、密度、树干基部断面积与城市森林降温作用关系不显著;郁闭度及树高与降温强度呈线性正相关,郁闭度每增加10%,降温效应增加0.5 ℃,树高每增加10 cm,降温效应增加0.05 ℃;叶面积指数与降温强度呈非线性正相关,叶面积指数对降温调节功能存在作用阈值,为0.23～2.3,叶面积指数位于该阈值内时,降温强度随叶面积的增加而迅速提高.

Cooling effects of urban forest community structure.

In this study, the influence of community structure on the cooling effect of urban forest was studied in Changchun by field sampling. The results showed that the temperatures of urban fore-sts with different canopy densities showed the same fluctuation trend with time. The temperature in urban forest was lower with higher canopy density. Community structure characteristics of urban fore-st affected the urban thermal environment. Among the structural indices used in this study, canopy density (CD), leaf area index (LAI) and tree height (H) had the most significant relationships with the cooling effect of urban forest, while stem density (SD), diameter at breast height (DBH) and base area (BA) had no significant influence on the thermal environment. CD and H were linearly correlated with the cooling intensity of urban forest, and cooling intensity increased by 0.5 ℃ for each 10% increase of canopy density and 0.05 ℃ for each 10 cm increase of tree height. There was a positive nonlinear correlation between the LAI and the cooling intensity. Further, a reasonable threshold of LAI for the cooling function was found in the range of 0.23-2.3. When the LAI was in the range of threshold value, the cooling intensity increased rapidly with the increase of LAI.