超纤渗灌对绿色屋顶土壤水分和蒸散发的影响

为研究超纤渗灌对绿色屋顶土壤水分及蒸散发的影响,以金鱼草、七里香、罗汉松、太阳花、多肉及佛甲草为试验材料,观测有无超纤渗灌处理下的绿色屋顶土壤含水率,并通过三温模型及蒸渗仪法测算不同植物的蒸腾速率及蒸散量,评估超纤渗灌对绿色屋顶蒸散发的影响。结果表明：超纤渗灌处理下的七里香、金鱼草及裸土种植盆内的平均土壤含水率分别比无超纤渗灌处理提高27%,18%及47%,超纤渗灌能增加土壤含水率,减少水分胁迫情况的发生。在夏季（雨季）,超纤渗灌处理的植物蒸腾速率总体显著（P<0.01）大于无超纤渗灌处理,且气温越高,植物冠层温度与气温温差越大。在冬季（旱季）,超纤渗灌能使屋顶基底温度平均高出0.25 ℃,减小温度变化振幅;超纤渗灌处理能使佛甲草夜间蒸散量增加0.14 mm,但白天有超纤渗灌的蒸散量比无超纤渗灌低了0.57 mm,总体减少了9.3%。超纤渗灌能提高绿色屋顶土壤含水率,在夏季增加植物蒸散量,在增加冬季夜间屋顶蒸散量的同时,也有利于绿色屋顶白天吸附空气水分,促进这一部分非降水资源的利用。

Effects of microfiber capillary wicking irrigation on soil moisture and evapotranspiration of green roofs

Abstract: Green roofs have drawn much more attention under the promotion of the Sponge City-Low Impact Development Rainwater System (LID) in modern urban construction and planning. Much more green roofs have been built so far. However, there is a great challenge on the later maintenance in the process of green roofs, such as the difficult irrigation, high cost, and large water consumption. Therefore, automatic irrigation is urgently needed suitable for roof greening. Taking the microfiber capillary as the material, this study aims to propose an automated irrigation technology for the roof green potted test, called the microfiber infiltration capillary irrigation (MCII). Taking the Antirrhinum majus, Murraya paniculata, Podocarpus macrophyllus, Portulaca grandiflora, succulent plant, and Sedum lineare as test plants, a systematic investigation was made to clarify the effects of MCII treatment on the soil water content and evapotranspiration of green roof. The transpiration rate and evapotranspiration amount were measured for the different plants in different seasons using the specific steaming instrument. A three-temperature model was established to evaluate the MCII performance on the evaporation of green roofs. The field experiment was carried out in the Zhuhai Campus, Sun Yat-sen University, Guangdong Province, China. The results showed that the average soil water contents of Murraya paniculata, Antirrhinum majus, and bare soil module with MCII were 27%, 18%, and 47% higher than those without MCII, respectively. The MCII increased the soil water content, further reducing the occurrence of water stress. The transpiration rate of Antirrhinum majus with MCII was significantly higher than that without MCII (P>0.01) in summer (rainy season). The average daily transpiration rates of Antirrhinum majus were more than 13.8, 39.2, 45.7, and 19.0 J/(m2·s) on April 8, May 18, June 29, and July 27, 2021, respectively. Simultaneously, the maximum transpiration rates with MCII were 22.3, 104.4, 94.0, and 30.8 J/(m2·s) higher than those without MCII, respectively. The largest difference in transpiration rate between MCII and non-MCII was at 12:00-14:00, the hottest period of the day. Correspondingly, the higher the temperature was, the greater the temperature difference between plant canopy and air surrounding. By contrast, the bottom temperature of the test module with the MCII was higher than that without MCII in winter (dry season), no matter the day and night. The MCII increased by 0.25 °C for the average temperature of the roof base, indicating a less temperature variation for the better energy storage of the green roof in winter. Evapotranspiration of Sedum line with MCII at night was 0.14 mm higher than that without MCII, but the MCII evapotranspiration in the daytime was 0.57 mm lower than that without MCII, indicating the overall decrease of 9.3% in the MCII treatment. The change was attributed to the formation of dew in the process. Consequently, the MCII can be used to improve the soil water content, the evapotranspiration of vegetation in summer, and to increase the roof evapotranspiration at night in winter. At the same time, it is also necessary to explore the air moisture for the green roof during the day, further to promote the non-precipitation resource. This finding can also provide sound theoretical support to the microfiber infiltration capillary irrigation for water-saving green roofs.