半湿润地区城市绿地灌木的截留集水功能及其影响因素

在半湿润地区,创新节水型城市绿地建设模式,实现绿地由耗水型向节水型转变,是学术界关注的热点问题。通过模拟降雨的方法,对半湿润地区城市绿地中的金叶女贞、大叶黄杨、小叶黄杨、红叶石楠、龙柏和侧柏等6种灌木的截留集水功能及其影响因素进行研究。结果表明: 冠层截留和茎流集水是水文过程的两个不同阶段,常绿灌木冠层截留大,但其茎流集水差;随着雨强增大,所有灌木的穿透雨率和茎流率都明显增加,但截留率却相对减少;穿透雨率表现为阔叶灌木显著大于针叶灌木,茎流率趋势与之相同,而截留率则相反。冠层投影中心区域穿透雨率最小,随着与冠层投影中心距离的加大,叶面积指数降低,穿透雨率也呈逐步减少趋势;当雨强为小雨时,冠层投影中心的穿透雨率小,即截留率和茎流率大,当雨强为大雨时,冠层投影中心的穿透雨率大,即截留率和茎流率小;随着雨强增大,冠层外围穿透雨率增大,漏斗形截留集水系统呈缩小趋势。雨强和叶面积指数是显著影响灌木截留集水功能的重要因素;半湿润地区城市绿地在林下配置阔叶灌木更有利于截留集水。

Canopy interception and water harvesting function of shrubs in urban green spaces of semi-humid region and their influencing factors

In the semi-humid region, developing innovative water conservation urban green space design and facilitating urban greening projects from high water consumption to water conservation are hot topics in research and practice. Using the simulated rainfall method, we explored the water interception and collection functions and their influencing factors of six shrub species (Ligustrum ×vicaryi, Euonymus japonicas, Buxus sinica var. parvifolia, Photinia ×fraseri, Juniperus chinensis and Platycladus orientalis) in urban green space in the semi-humid region. The results showed that canopy interception and water harvesting were two stages in hydrological processes. The canopy interception of coniferous shrubs was high, while their stemflow was low. When the rainfall intensity increased, throughfall rates and stem-flow rates of all shrub species increased significantly, while the interception rate relatively decreased. The throughfall and stem-flow rates of broad-leaved shrubs were significantly higher than those of coniferous shrubs. The canopy interception was significantly lower in broad-leaved shrub species than in coniferous ones. At the center of canopy projection, the throughfall rate was the lowest. The leaf area index (LAI) and throughfall rate decreased gradually from the center of the canopy projection area. When the rainfall intensity was small, the throughfall rate at the center of canopy projection area was low, and thus the interception rate and the stem-flow rate were higher. When the rainfall intensity was more elevated, throughfall at the center of canopy projection area was large, and thus the interception rate and the stem-flow rate were low. With increasing rainfall intensity, the funnel-shaped water collection system tended to shrink due to the increases of throughfall rate at the edge of canopy. Rainfall intensity and LAI were the most critical factors affecting water harvesting function. Planting broad-leaved shrubs under the forest may be more effective in water harvesting than planting coniferous shrubs.