Lundholm Jeremy, Heim Amy, Tran Stephanie, Smith Tyler
Departments of Biology and Environmental Science, Saint Mary's University, Halifax, Nova Scotia, Canada.
Eastern Cereal and Oilseen Resarch Centre, Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada.
PLoS One. 2014 Jun 30;9(6):e101395. doi: 10.1371/journal.pone.0101395. eCollection 2014.
Green roof ecosystems are constructed to provide services such as stormwater retention and urban temperature reductions. Green roofs with shallow growing media represent stressful conditions for plant survival, thus plants that survive and grow are important for maximizing economic and ecological benefits. While field trials are essential for selecting appropriate green roof plants, we wanted to determine whether plant leaf traits could predict changes in abundance (growth) to provide a more general framework for plant selection. We quantified leaf traits and derived life-history traits (Grime's C-S-R strategies) for 13 species used in a four-year green roof experiment involving five plant life forms. Changes in canopy density in monocultures and mixtures containing one to five life forms were determined and related to plant traits using multiple regression. We expected traits related to stress-tolerance would characterize the species that best grew in this relatively harsh setting. While all species survived to the end of the experiment, canopy species diversity in mixture treatments was usually much lower than originally planted. Most species grew slower in mixture compared to monoculture, suggesting that interspecific competition reduced canopy diversity. Species dominant in mixture treatments tended to be fast-growing ruderals and included both native and non-native species. Specific leaf area was a consistently strong predictor of final biomass and the change in abundance in both monoculture and mixture treatments. Some species in contrasting life-form groups showed compensatory dynamics, suggesting that life-form mixtures can maximize resilience of cover and biomass in the face of environmental fluctuations. This study confirms that plant traits can be used to predict growth performance in green roof ecosystems. While rapid canopy growth is desirable for green roofs, maintenance of species diversity may require engineering of conditions that favor less aggressive species.
绿色屋顶生态系统的构建旨在提供诸如雨水截留和降低城市温度等服务。生长介质浅薄的绿色屋顶对植物生存而言条件恶劣，因此能够存活并生长的植物对于实现经济和生态效益最大化至关重要。虽然田间试验对于选择合适的绿色屋顶植物必不可少，但我们想确定植物叶片性状是否能够预测丰度变化（生长情况），从而为植物选择提供一个更通用的框架。我们对13个物种的叶片性状进行了量化，并推导了其生活史性状（格兰姆的C-S-R策略），这13个物种被用于一项为期四年的绿色屋顶实验，该实验涉及五种植物生活型。我们确定了单一栽培以及包含一至五种生活型的混合栽培中冠层密度的变化，并使用多元回归分析将其与植物性状相关联。我们预计与耐逆性相关的性状将是最适合在这种相对恶劣环境中生长的物种的特征。虽然所有物种都存活到了实验结束，但混合处理中的冠层物种多样性通常远低于最初种植的水平。与单一栽培相比，大多数物种在混合栽培中的生长速度较慢，这表明种间竞争降低了冠层多样性。在混合处理中占主导地位的物种往往是快速生长的杂草类植物，包括本地和非本地物种。比叶面积始终是单一栽培和混合栽培中最终生物量以及丰度变化的有力预测指标。一些处于不同生活型组的物种表现出补偿动态，这表明生活型混合能够在面对环境波动时使覆盖度和生物量的恢复力最大化。本研究证实植物性状可用于预测绿色屋顶生态系统中的生长表现。虽然绿色屋顶需要冠层快速生长，但维持物种多样性可能需要设计有利于竞争力较弱物种的条件。
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