Plants make important contributions to green roof ecosystem service provision through evapotranspiration, canopy shading, and water retention. Because these plant communities are a critical component of green roof design and function, both seasonal and interspecific variation of these plant communities are important factors in evaluating green roof performance. This study examines variation in both species abundance and 9 leaf traits throughout the 2015 growing season of four New York City green roofs. While community composition varied significantly between each month (p_ANOSIM = 0.036), three major plant families (Asteraceae, Lamiaceae, and Poaceae) consistently had the greatest green cover and were present during the entirety of the growing season. For leaf traits, period of the growing season had a significant impact on most of the traits measured. Leaf thickness, leaf relative water content (RWC) and saturated water content (SWC) decreased as the growing season progressed, while leaf dry matter content (LDMC) and stomatal density increased, likely due to a seasonal decrease in rainfall as species-level variance in these water traits is low (7.40% and 0.88%, respectively). We also ranked planted and spontaneous species in accordance to both cover and functional trait values, and identified 11 species suitable for green roofs in NYC: Pycnanthemum tenuifolium (Lamiaceae), Symphiotrichum leave, Symphiotrichum pilosum, Rudbeckia hirta, Solidago odora (Asteraceae), Panicum virgatum, Sorghastrum nutrans, Schizachyrium scoparium, Dichanthelium clandestinum, Deschampsia flexuosa (Poaceae), and Oenothera biennis (Onagraceae). Understanding the temporal responses of plant communities and their constituent species is critical in optimizing green roof ecosystem services.

植物通过蒸发蒸腾、树冠遮荫和保水，为屋顶绿化生态系统服务做出了重要贡献。由于这些植物群落是屋顶绿化设计和功能的重要组成部分，因此这些植物群落的季节性和种间变化是评估屋顶绿化性能的重要因素。本研究调查了整个 2015 年纽约市四个绿色屋顶的物种丰度和 9 个叶子特征的变化。虽然每个月的群落组成差异很大（p _ANOSIM = 0.036)，三个主要植物科（菊科、唇形科和禾本科）始终具有最大的绿色覆盖，并且在整个生长季节都存在。对于叶片性状，生长季节的时间对测量的大多数性状有显着影响。随着生长季节的推进，叶片厚度、叶片相对含水量 (RWC) 和饱和含水量 (SWC) 下降，而叶片干物质含量 (LDMC) 和气孔密度增加，这可能是由于物种水平差异导致降雨的季节性减少在这些水中性状中较低（分别为 7.40% 和 0.88%）。我们还根据覆盖度和功能性状值对种植和自发物种进行了排名，并确定了 11 种适合纽约市绿色屋顶的物种：Pycnanthemum tenuifolium（唇形科）、Symphiotrichum休假，Symphiotrichum pilosum，黑心菊，一枝odora（菊科），柳枝稷，Sorghastrum nutrans，裂稃花棒，渐尖二型花狼尾草，曲芒发草（禾本科），和月见草（柳叶菜科）。了解植物群落及其组成物种的时间响应对于优化屋顶绿化生态系统服务至关重要。