Abstract:

An experiment was conducted to study the effects of storage layer and plant selection on the evapotranspiration of green roofs quantitatively. By setting 4 pilot green roofs designed with different structures and different vegetation, the variation of evapotranspiration (ET), soil moisture content and the corresponding weather conditions were monitored and recorded. The results show that, for both of the green roofs vegetated with Sedum lineare and Callisia repens, the water evaporated from the storage layer plays the role in the recharge of the moisture content of the upper soil layer. In addition, it shows a positive correlation between the initial soil moisture content and daily evapotranspiration in varying degrees during drought periods. The setting of storage layer would increase the evapotranspiration of a green roof. However, the correlation level of the green roof vegetated with Sedum lineare is lower than that with Callisia repens, due to its complexity and particularity of the crassulacean acid metabolism (CAM) mode, and the hourly evapotranspiration fluctuates greatly. Different from Callisia repens, the stomas would close when the solar radiation is very strong to reduce the amount of transpiration and retain water. It would provide a theoretical basis for the assessment of ecological benefits on evapotranspiration of green roofs.

Key words: green roof, storage layer, plant selection, evapotranspiration

摘要：

为定量研究蓄水层设置和植物选择对绿色屋顶蒸散发的影响, 设置两种结构(有或无蓄水层)和两种植物(佛甲草和铺地锦竹草)共4种组合的绿色屋顶实验槽, 在深圳市的气候条件下, 连续测定气象参数、绿色屋顶蒸散发量(ET)和土壤含水量。结果表明, 蓄水层的水分蒸发对其上层土壤水分有显著的补给效应, 且土壤含水量与日蒸散发量存在正相关关系, 因此蓄水层的设置可以增加绿色屋顶的蒸散发量。佛甲草因其景天酸代谢方式(CAM)的特殊性, 当太阳辐射较大时, 气孔自动关闭, 从而降低蒸散发量, 减少水分流失。与铺地景竹草相比, 种植佛甲草的实验槽一天内的小时蒸散发量波动较大, 中午前后出现低谷, 与土壤含水量的相关程度相对较低。

关键词: 绿色屋顶, 蓄水层, 植物选择, 蒸散发