湿热地区简单式屋顶绿化的截流雨水效应

城市内涝是困扰各大城市的环境问题,其主观原因是来自迅速增加的城市不透水面.国外运用屋顶绿化作为截留雨水的措施得到广泛实践,而屋顶绿化滞留雨水能力随气候条件的变化而变化.湿热气候区具有气温高、湿度高、雨量大的气候特点,在此气候条件下探讨屋顶绿化截留雨水的效能具有重要意义.本研究以在夏季雨热同期的广州市为例,搭建3个简单式屋顶绿化测试平台,通过13个月试验期的气象观测和数据测定推算其截留雨水的效能.结果表明: 基质厚度30、50和70 mm简单式屋顶绿化的降雨滞留率分别为27.2%、30.9%和32.1%,平均峰值减少量为18.9%、26.2%和27.7%.广州市建成区面积1035.01 km²,屋顶面积约占37.3%,假设在此区域推行30 mm厚度基质的屋顶绿化,小、中、大雨的总迟滞比率分别为72.8%、22.6%和17.4%,以此推算得出可滞留雨水体积达14317×10⁴ m³,说明简单式屋顶绿化的截留雨水效应具有巨大潜力.本研究结果可为湿热气候区城市缓解城市内涝、建设海绵城市的构想提供参考.     

基于市政污泥的拓展型绿色屋顶基质的固碳潜力研究

为提高固体废弃物资源化利用率, 探索绿色屋顶基质的固碳能力, 推广绿色屋顶的应用, 研究选择混合污泥土(污泥与自然土等体积混合)和本地自然土作为绿色屋顶的种植基质, 分别修建20 cm、25 cm和30 cm三个不同厚度的绿色屋顶, 进行了一年的对比试验。结果表明: 混合污泥土平均总碳含量较高, 为(44.33±7.12) g⋅kg–1, 平均总有机碳(36.02±6.03) g⋅kg–1高于自然土的总有机(19.64±4.3) g⋅kg–1。混合污泥土TC与TOC含量随土层深度的增加降低规律不明显, 而自然土比较明显。混合污泥土的碳密度(13.15 kg⋅m–2)是本地自然土(8.58 kg⋅m–2)的1.53倍, 一年的固碳量混合污泥土(3.81 kg⋅m–2)与自然土(3.89 kg⋅m–2)相当, 两者的固碳能力都处于较高水平。可见混合污泥土是一种潜力较大的绿色屋顶种植基质。若将成都市34 km2没有绿化的屋顶面积的50%选择混合污泥土作为绿色屋顶基质进行推广应用, 成都绿色屋顶基质每年增加固碳6.48×107kg, 相当于每年减少CO2排2.38×108kg, 利用市政污泥2.125×106m3(2.231×106 t), 这将对成都市固体废弃物资源化利用和成都“世界现代田园城市”的建设起十分积极的作用。     

半干旱黄土丘陵区撂荒坡地土壤水分循环特征

为深入了解半干旱黄土丘陵区土壤水分循环特征和为开展荒地造林工作提供背景数据,在宁南上黄生态试验站,选取典型多年撂荒坡地,进行土壤水分的长期定位观测,分析其土壤水分补给、消耗特征与时空变异性。结果表明:研究区降雨入渗量和入渗深度随降雨量增加而增加,入渗补给系数约为0.44,雨水资源化率有待提高。定义全年一半以上的次降水事件中能被有效补给的土层深度为降水普遍入渗深度,则研究区降水普遍入渗深度为0—40 cm,观测期内最大入渗深度不超过300 cm。同时,土壤水分的蒸散发量在丰水年平水年干旱年,主要蒸散发作用层位于0—200 cm土层范围内,最大蒸散发深度达到300 cm以下。该区土壤储水量的季节变化为"V"型,剖面土壤平均含水量的垂直变异则呈现反"S"型。土壤水分的变异系数随土层深度的增加表现出幂函数递减趋势,结合有序聚类法的分层结果,可采用0.20和0.05两个CV值将撂荒地土壤剖面划分为水分活跃层(0—40 cm)、次活跃层(40—200 cm)和相对稳定层(200 cm以下)3个层次。     

黑河流域高寒草甸生态系统水分收支及蒸散发拆分研究

水分收支是对水循环要素降水、蒸发蒸腾、径流以及土壤贮储水量变化等的定量刻画,对水资源的可持续开发及利用至关重要。基于黑河流域阿柔观测站2014和2015年水文气象观测数据,运用水量平衡理论,定量的评估了高寒草甸生态系统的水分收支动态,并结合双源模型对高寒草甸生态系统蒸散发(植被蒸腾和土壤蒸发)进行拆分及评价。研究结果表明(1)在生长季(5—9月)植被蒸腾是高寒草甸生态系统主要的耗水形式,2014和2015年生长季平均蒸散比(T/ET)分别为0.74和0.79;(2)土壤水分的剧烈变化主要发生在0—40 cm处,且受冻融过程影响显著;(3)在降水较多的年份(2014)高寒草甸生态系统水分收支基本平衡,且不受冻融影响的月份(6—9)有地表径流产生约42 mm;在正常年份(2015),生态系统呈现水分亏缺,亏缺量约为134 mm,6—9月约亏缺26 mm;(4)模型估算蒸散发(ET)与实测蒸散发具有很好的一致性,相关系数可达0.90,敏感性分析表明模型输入变量对蒸散发(ET)及蒸散比(T/ET)产生的误差较小,双源模型可以很好地实现对高寒草甸生态系统蒸散发(ET)的拆分。     

南京地区蒸散发降尺度研究--基于增强型时空自适应反射融合模型

蒸散发是水文循环的重要组成部分,获取高时空分辨率的数据能够更加精细化蒸散发的时空变化规律,对于水资源管理、生态水文过程量化具有重要意义。由于单一传感器反演的蒸散发无法同时具有高空间和高时间分辨率,以南京地区为例,首先结合Landsat-8遥感影像数据和气象数据,采用基于能量平衡原理的SEBS模型估算日蒸散量。在此基础上,选取典型区域采用基于增强型时空自适应反射融合模型(ESTARFM)将估算的蒸散发结果与低空间分辨率的MOD16A2蒸散发产品数据进行时空融合降尺度研究,并评价模型的融合精度。结果表明:(1)SEBS模型估算的蒸散发结果与蒸发皿折算后的数据、MOD16A2产品数据的平均相对误差分别为0.14 mm/d和0.22 mm/d。(2)南京地区蒸散量季节差异明显,表现为夏季＞秋季＞冬季;各区在夏季的日平均蒸散量差异也较大,六合区蒸散量最大,秦淮区最小;另外,蒸散量分布受土地利用类型的影响,总体上表现为水域＞林地＞耕地＞草地＞其他,且植被覆盖度较高的区域蒸散量较大。(3)基于ESTARFM模型融合的蒸散发结果与基于Landsat-8遥感影像反演的蒸散发数据在空间分布上具有相似性,二者相关系数为0.74。在全球气候变化的背景下,本研究可为蒸散发数据集时空分辨率的提高提供参考,同时也能够为南京地区水循环过程和水资源管理研究提供数据支撑。     

黑河上游天涝池流域草地蒸散发特征及蒸发皿系数研究

选择黑河上游天涝池流域为研究区, 利用Lysimeter 蒸散仪和蒸发皿, 对亚高山草地蒸散发和水面蒸发进行实际观测。结果表明: 在月尺度上, 从4 年的平均看, 6 月最大, 其次是8 月, 7 月最小; 6、7 和8 月的日均蒸散发量都是在2013年最大, 其次为2011 年, 然后是2014 年, 2012 年最小; 2011 和2012 年中, 每月的日均蒸散发量大小顺序为6 月>8 月>7 月;在2013 年中, 8 月份日均蒸散发量最大, 其次为6 月份, 7 月份的日均蒸散发量最小; 但在2014 年中, 7 月份的日均蒸散发量最大, 8 月份和6 月份的相对较小。草地日均蒸散发量成波动状态, 与降雨有一定的关系, 降雨在一天内出现的时间不同, 对蒸散发的影响也不尽相同。日蒸散发量与环境因子之间的相关关系为: 风速>饱和水汽压差>相对湿度>净辐射, R² 分别为0.4174、0.3598、0.3461 和0.3322, 四个气象因子对日蒸散发量都有较大的影响。通过对典型晴天下小时尺度实际蒸散发量与蒸发皿蒸散发量的关系的分析, 将蒸发皿系数分为8:00-14:00 和14:00-20:00 两个时间段和8:00-20:00 整个时间段来计算, 8:00- 14:00 和14:00-20:00 时间段的蒸发皿系数分别大于1 和小于1, 而8:00-20:00 整个时间段蒸发皿系数小于1。     

基于SEBAL模型的西北农牧交错带生长季蒸散发估算及变化特征分析

蒸散发是土壤-植被-大气系统中水循环和能量交换的主要组成部分,准确估算区域蒸散发对农业用水调度与水资源的管理至关重要。利用MODIS数据产品结合地面气象站的观测资料,基于能量平衡原理建立的SEBAL(Surface Energy Balance Algorithms for Land)模型对西北农牧交错带2015年生长季(4—10月)的地表蒸散发量进行反演研究,并用Penman-Monteith(P-M)公式结合作物系数对模型的估算结果进行对比,结果表明:SEBAL模型估算结果与P-M公式之间的平均绝对误差为0.79mm/d,均方根误差为0.94mm/d,R~2=0.76,整体反演值偏高,但基本能满足本地区的研究需求。生长季区域日均蒸散发的变化范围为0.12—10.66mm/d,日蒸散量均值为4.31mm/d,呈东北、西南部较高,西部偏低的空间分布特征。将蒸散发估算值与地表特征参数统计分析发现蒸散发与NDVI和地表净辐射之间呈正相关,与地表温度和地表反照率之间呈负相关;不同土地利用/覆被类型的日蒸散发量由大到小依次为:耕地、林地、未利用地与草地。     

基于改进的双源模型模拟荒漠河岸胡杨林蒸散发

蒸散发是水循环和能量平衡过程中的重要组成部分,其准确量化对于深刻揭示干旱半干旱地区的生态水文过程具有重要意义。以黑河下游荒漠河岸胡杨林为研究对象,在2014和2015年胡杨主要生长季内,基于涡度相关技术实测数据,分析了蒸散发日及各物候期变化规律,结合改进的双源Penman-Monteith-Priestley-Taylor(PM-PT)模型,模拟了黑河下游荒漠河岸胡杨林蒸散发,并分析了模型的参数敏感性,得到的主要结论如下:(1)胡杨林蒸散发日变化大致呈先升高后降低的趋势。上午随着太阳辐射的逐渐增强,气温逐渐升高,蒸散速率逐渐增大,在中午12:00左右达到峰值。随后,太阳辐射减弱,气温逐渐降低,空气中相对湿度增加,胡杨叶片内外水汽压差减小,蒸散速率随之降低。(2)胡杨生长季内蒸散发整体上呈先升高后降低的趋势。2014和2015年生长季蒸散发总量分别为612 mm和658 mm,果期和种子散播期累积蒸散发为生长季内蒸散发总量的主体部分,果期内累积蒸散发分别为316 mm和348 mm,分别占各年生长季蒸散发总量的51.65%和52.87%;种子散播期内平均蒸散发略低于果期,2014和2015年胡杨林种子散播期内累积蒸散发分别为261 mm和271 mm,分别占各年生长季蒸散发总量的42.71%和41.12%,展叶期和叶变色期内平均蒸散发最低,原因在于展叶期胡杨叶片尚未完全成形,而叶变色期叶片活性逐渐降低。(3)改进的双源PM-PT模型与传统的双源Shuttleworth-Wallace(SW)模型相比,在模型结构与参数数量方面均得到了优化,其模拟精度也更高。(4)改进的双源PM-PT模型对净辐射最为敏感。     

基于Budyko假设的潮河流域气候和植被变化对实际蒸散发的影响研究

由于参数较少且具有明确的物理学意义,基于水热平衡理论的Budyko假设常用于定量分析以及评价气候变化和植被变化对实际蒸散发的影响,对研究流域水量平衡和能量分配具有重要意义。依据位于我国北方密云水库上游的潮河流域1961—2015年的水文气象数据,选取了4种基于Budyko假设的模型来研究潮河流域水热耦合平衡关系,确定了该流域最适用模型以及模型参数最优值,并且采用情景设置法分析了流域实际蒸散发对气候以及植被变化的响应。结果表明:(1)与经典Budyko模型相比,采用流域下垫面参数修正的Budyko模型计算实际蒸散发的精度更高。其中,傅抱璞模型精度最高,决定系数、相对误差、纳什效率系数和均方根误差分别为0.85、4.30%、0.82和27.66 mm;(2)对傅抱璞模型下垫面参数ω进行优化,确定适用于潮河流域的模型参数取值为2.54,优化后的傅抱璞模型能够更好地反映流域实际蒸散发的变化特征;(3)情景模拟表明,气候变化和植被变化的共同作用导致潮河流域实际蒸散发的上升。其中,气候变化是引起流域蒸散发变化的主要驱动因素。     

元江干热河谷林地内外潜在蒸散发量的变化及其驱动因素

蒸散发对把握气候变化、理解区域生态保护具有重要意义。本文利用主成分分析及皮尔逊双侧相关检验的方法研究元江干热河谷林地内外潜在蒸散发量(PET)的变化及其驱动因素,并根据分析结果对林地内外蒸散发的发生过程进行解读。通过对2015—2018年日PET的研究发现:林内PET比林外低0.86 mm·d^-1;林地内外PET呈周期式减小,林外的减小趋势更大。2015—2018年及对应年份旱雨季的林地内外干旱指数显示,元江的干旱程度在研究时间段内有所缓解,林内干旱指数较林外更低。林内日PET的驱动因素依次是气温(Ta)、地面净辐射(Rn)、5 cm土壤热通量;林外日PET的驱动因素依次是Ta、5 cm土壤温度、Rn。林内蒸散发的发生层按蒸散发的剧烈程度所划分的层次性较清晰,剧烈层位于稀树灌丛林型的中上层,蒸散发的剧烈程度由中上层向下依次减弱;林外蒸散发的发生层层次性较混合,剧烈层位于近地面空气与土壤交汇层。     

The role of vegetation in regulating stormwater runoff from green roofs in a winter rainfall climate

Extensive green roofs composed of a thin layer of growing medium topped with vegetation can significantly reduce both the timing and magnitude of stormwater runoff relative to a typical impervious roof. However, regional climatic conditions such as seasonality in rainfall and potential evapotranspiration could strongly alter the stormwater performance of green roofs. In this study we evaluate the stormwater performance of green roofs in the predominately winter rainfall climate of the U.S. Pacific Northwest. We also test whether the amount of irrigation used to maintain green roof vegetation in a seasonally dry climate such as the Pacific Northwest influences stormwater performance. We monitored stormwater performance over one year for sets of experimental roofs constructed using three designs: a conventional impervious design, a medium-only design, and a typical extensive green roof design that included vegetation. During the winter rainy season vegetation had no significant influence on stormwater retention; medium-only and vegetated roofs reduced stormwater runoff nearly identically relative to the impervious roofs. In contrast, during summer vegetated roofs retained significantly more rainfall than medium-only roofs, although this effect depended strongly on the size of the rain event. In addition, total relative retention for both roof types was significantly higher during summer than during winter. Irrigation significantly reduced summer retention capacity of both medium-only and planted roofs, but only during the largest dry season rain event. These results suggest that cool wet season climates such as the Pacific Northwest are challenging ones for green roof stormwater performance. In order to optimize stormwater benefits of green roofs, designers should create explicitly regional designs that include plant selections better matched to the specific environmental and management constraints.     

Hydrological performance of extensive green roofs in response to different rain events in a subtropical monsoon climate

Rapid urbanization transforms permeable land into developed areas with predominantly impervious surfaces, significantly increasing stormwater runoff and exacerbating the risk of pluvial flooding. Green roofs provide an attractive strategy for increasing surface permeability by mimicking pre-development hydrologic functions and mitigating flood risks in compact cities. However, the potential of this strategy has not been rigorously assessed, despite advances in global stormwater management. This is mainly due to insufficient scientific knowledge of hydrologic performance and a lack of experimental studies of rainwater-harvesting capacity under specific climatic conditions. This study evaluated the hydrologic performance of a real-scale extensive green roof (EGR) constructed in a subtropical monsoon climate in Nanjing, China. Overall, the EGR showed considerable ability to retain rainfall (mean retention ~?60%, accumulated retention ~?30%), although retention performance varied from 11% to 100% depending on the rainfall event considered, and decreased with increasing rainfall. Event-based rainfall–runoff comparisons demonstrated that the EGR retained rainwater efficiently during the early stages of a rainfall event and significantly attenuated peak runoff flows compared to bare roofs. Statistical analysis showed that total rainfall depth, rainfall duration, and substrate layer moisture influenced the overall retention most strongly, but also the percentage retention and runoff depth, highlighting the impact of substrate properties in addition to rainfall characteristics on EGR hydrologic performance. These findings provide new knowledge of and important insights into the hydrological performance of green roofs in subtropical monsoon climates, which could be used to guide EGR construction to increase landscape permeability, mitigate the risk of pluvial flooding, and enhance the climatic resilience of urban regions.

     

高度城市化地区屋顶绿化径流调控效益评价——以厦门岛为例

屋顶绿化的降雨径流调控效益对城市水安全与可持续发展具有重要作用,尤其是在土地资源紧缺与环境问题突出的高度城市化地区,然而目前针对城市尺度进行屋顶绿化降雨径流调控效益的研究较少。以厦门岛142 km~2的典型高度城市化地区为研究对象,采用ArcGIS与SCS-CN水文模型,研究了四种屋顶绿化实施场景在四种不同重现期(2、5、10、20年)降雨事件下各汇水区屋顶绿化的降雨径流调控效益,并依其空间分异特征制定差异化生态建设策略。结果显示,(1)平均地表径流减少率随城市屋顶绿化量的增加从0.91%增加至4.51%,随降雨强度的增加从2.86%下降到2.01%。屋顶绿化对南部城市核心区中山路商圈汇水区的地表径流削减作用最为显著,在2年重现期降雨事件和100%屋顶绿化实施场景下地表径流减少了8.84%。(2)厦门岛易积水区域主要分布在高崎机场、西北部港口、筼筜湖、五缘湾和环岛路;在四种屋顶绿化实施场景下,平均积水深度降低1.68、4.68、6.45、14.43 cm,平均积水面积减少6.11、16.89、23.29、52.06 hm~2,而随着降雨强度的增加,积水面积减少率幅度降低,屋顶绿化对中低...     

Multifunctionality is affected by interactions between green roof plant species,substrate depth,and substrate type

Green roofs provide ecosystem services through evapotranspiration and nutrient cycling that depend, among others, on plant species, substrate type, and substrate depth. However, no study has assessed thoroughly how interactions between these factors alter ecosystem functions and multifunctionality of green roofs. We simulated some green roof conditions in a pot experiment. We planted 20 plant species from 10 genera and five families (Asteraceae, Caryophyllaceae, Crassulaceae, Fabaceae, and Poaceae) on two substrate types (natural vs. artificial) and two substrate depths (10 cm vs. 30 cm). As indicators of major ecosystem functions, we measured aboveground and belowground biomasses, foliar nitrogen and carbon content, foliar transpiration, substrate water retention, and dissolved organic carbon and nitrates in leachates. Interactions between substrate type and depth strongly affected ecosystem functions. Biomass production was increased in the artificial substrate and deeper substrates, as was water retention in most cases. In contrast, dissolved organic carbon leaching was higher in the artificial substrates. Except for the Fabaceae species, nitrate leaching was reduced in deep, natural soils. The highest transpiration rates were associated with natural soils. All functions were modulated by plant families or species. Plant effects differed according to the observed function and the type and depth of the substrate. Fabaceae species grown on natural soils had the most noticeable patterns, allowing high biomass production and high water retention but also high nitrate leaching from deep pots. No single combination of factors enhanced simultaneously all studied ecosystem functions, highlighting that soil–plant interactions induce trade‐offs between ecosystem functions. Substrate type and depth interactions are major drivers for green roof multifunctionality.     

Performance of dryland and wetland plant species on extensive green roofs

Background and Aims

Green roofs are constructed ecosystems where plants perform valuable services, ameliorating the urban environment through roof temperature reductions and stormwater interception. Plant species differ in functional characteristics that alter ecosystem properties. Plant performance research on extensive green roofs has so far indicated that species adapted to dry conditions perform optimally. However, in moist, humid climates, species typical of wetter soils might have advantages over dryland species. In this study, survival, growth and the performance of thermal and stormwater capture functions of three pairs of dryland and wetland plant species were quantified using an extensive modular green roof system.

Methods

Seedlings of all six species were germinated in a greenhouse and planted into green roof modules with 6 cm of growing medium. There were 34 treatments consisting of each species in monoculture and all combinations of wet- and dryland species in a randomized block design. Performance measures were survival, vegetation cover and roof surface temperature recorded for each module over two growing seasons, water loss (an estimate of evapotranspiration) in 2007, and albedo and water capture in 2008.

Key Results

Over two seasons, dryland plants performed better than wetland plants, and increasing the number of dryland species in mixtures tended to improve functioning, although there was no clear effect of species or habitat group diversity. All species had survival rates >75 % after the first winter; however, dryland species had much greater cover, an important indicator of green roof performance. Sibbaldiopsis tridentata was the top performing species in monoculture, and was included in the best treatments.

Conclusions

Although dryland species outperformed wetland species, planting extensive green roofs with both groups decreased performance only slightly, while increasing diversity and possibly habitat value. This study provides further evidence that plant composition and diversity can influence green roof functions.     

Temperature regime of planted roofs compared with conventional roofing systems

This paper analyses the temperature regime of an existing green roof and a sod roof, compared with a modified bituminous membrane roof and a steel sheet roof. The measurement period was from June 2004 to December 2007 at three different measurement locations. Results are given both seasonally and daily; indexes to characterize the effects of the temperature of planted roofs are also proposed. In summer, temperatures under both the green roof (100 mm) and the sod roof (150 mm) showed a similar temperature run; undesirable higher temperatures on the surfaces did not cause a notable increase in temperature under the substrate layers. The difference between the temperature amplitude under the substrate layers of the planted roofs and the surfaces of the conventional roofs was on average 20 °C. In autumn and spring, the sod roof's soil layer showed higher temperatures and lower amplitude than the green roof's substrate layer, which cooled more. In winter, temperatures under the substrate layers of the planted roofs were higher than the surfaces of the conventional roofs; average amplitude was 1 °C and 7–8 °C, respectively.     

Performance evaluation of native plants suited to extensive green roof conditions in a maritime climate

Assessing plant species performance on extensive green roofs can inform about and improve green roof functioning, aesthetics, longevity and the diversity of plant palettes available for the green roof industry. In this study, we evaluate survival, cover, roof cooling and stormwater retention properties of 15 plant species native to coastal regions of Atlantic Canada in extensive green roof monocultures. After a complete growing season (May-October 2009), all but one species had greater than 80% survival, and 10 species reached greater than 90% groundcover. Over the growing season, the top performing species reduced roof surface temperature by an average of 3.44 °C and increased solar reflectivity by 22.2% over the growing-medium only controls. Moreover, the best species retained 75.3% of experimentally added stormwater. Our results demonstrate that several species (mainly graminoids) performed better than creeping shrubs and forbs for most functions, although significant variation existed within life-form groups.     

亚热带季风区城市典型绿化屋顶的径流削减效应

屋顶绿化能够削减暴雨径流,降低城市内涝发生频率,促进可持续雨洪管理。针对亚热带季风气候区典型绿化屋顶的全年径流削减效应,以南京为研究区,以简易型、花园型两类绿化屋顶为研究对象,基于1年现场观测数据及水量平衡方程,分析屋顶雨水的滞蓄、蒸发与径流量随季节变化规律及其关键影响因子,采用SCS-CN模型计算绿化屋面的径流曲线数(CN),并估算城市尺度大面积屋顶绿化的暴雨径流削减效果。结果显示,简易型、花园型绿化屋顶全年径流削减率分别为42%和60.7%;径流削减效应的四季排序为春季冬季秋季夏季,平均径流削减率依次为78.6%、47.5%、33.2%、32.9%(简易型)及98%、84.3%、49.5%、48.1%(花园型);土壤基质层对雨水截留起主导作用,分别占径流削减总量的52%和62%;雨量和雨强是影响径流削减效应的关键因子,与径流削减率均呈显著负相关关系(P0.01),初始土壤湿度与简易型绿化屋顶的径流削减率呈显著负相关(0.01P0.05),但与花园型的径流削减率无显著相关性;基于全年77次降雨事件的降雨量-径流量数据测算得到简易型和花园型绿化屋顶的CN值分别为92和88;若南京主城区所有建筑屋顶面积的60%实施两类绿化,则其全年径流量可分别削减2.8×10~7 m~3和4.2×10~7 m~3。以上研究结果可为城市雨洪管理和海绵城市建设提供科学依据。     

Plant Species and Functional Group Combinations Affect Green Roof Ecosystem Functions

Background

Green roofs perform ecosystem services such as summer roof temperature reduction and stormwater capture that directly contribute to lower building energy use and potential economic savings. These services are in turn related to ecosystem functions performed by the vegetation layer such as radiation reflection and transpiration, but little work has examined the role of plant species composition and diversity in improving these functions.

Methodology/Principal Findings

We used a replicated modular extensive (shallow growing- medium) green roof system planted with monocultures or mixtures containing one, three or five life-forms, to quantify two ecosystem services: summer roof cooling and water capture. We also measured the related ecosystem properties/processes of albedo, evapotranspiration, and the mean and temporal variability of aboveground biomass over four months. Mixtures containing three or five life-form groups, simultaneously optimized several green roof ecosystem functions, outperforming monocultures and single life-form groups, but there was much variation in performance depending on which life-forms were present in the three life-form mixtures. Some mixtures outperformed the best monocultures for water capture, evapotranspiration, and an index combining both water capture and temperature reductions. Combinations of tall forbs, grasses and succulents simultaneously optimized a range of ecosystem performance measures, thus the main benefit of including all three groups was not to maximize any single process but to perform a variety of functions well.

Conclusions/Significance

Ecosystem services from green roofs can be improved by planting certain life-form groups in combination, directly contributing to climate change mitigation and adaptation strategies. The strong performance by certain mixtures of life-forms, especially tall forbs, grasses and succulents, warrants further investigation into niche complementarity or facilitation as mechanisms governing biodiversity-ecosystem functioning relationships in green roof ecosystems.