选择广州市8种常见绿化树木,测试其叶片的蒸腾强度和绿地叶面积指数.计算绿地的蒸腾强度.据此算出绿地的降温和增湿效能,并与同步观测的绿化、未绿化地区的气温差、温度差作对照.两者变化趋势一致,数值大小相近似.单位绿地面积的树木蒸腾使周围大气降温和增湿的数值大小,因影响范围和树种不同而异.随之概算了广州为改善城市热岛效应所需的绿地面积,探讨了城市绿化定额指标问题.

Observed are the transpiration ratio of leaf blades and the leaf blade area index on greenlands with eight selected common afforestation trees in Guangzhou.By calculating greenland transpiration the decrease of temperature and the increase of humidity are deduced.Synchronous observations are made of temperature and humidity in afforestation areas and nonafforestation areas.Comparison between the results from calculations and from observations shows tendencies are identical and numerical values are approximate.The effects of decreasing temperature and increasing humidity of afforestation may vary,depending on the area and the kings of trees,Afforestation areas are proposed for improving urban heat effect in Guangzhou.