Extensive green roof (EGR) substrates and vegetation layer are critical components to ensure EGR multifunctionality. However, little is known on EGR substrate biological functioning, especially nutrient cycling that is crucial for supporting life in soils. This work aimed at investigating for the first time the effectiveness of an affordable and easy-to-use standardized method, the cotton-strip assay, to assess decomposition rates in ten-year old EGR. Three metrics were evaluated following 34–110 days of cotton-strip incubation into substrates: tensile strength, weight and surface area losses. Tensile strength loss was the most sensitive index after 34 days while weight loss over 110 days confirmed elevated decomposition rates in EGR substrates compared to gravel rooftop or common urban park soil. This could be related to positive influence of slightly acidic pH and vegetation cover. Finally, semi-intensive but thin green roof substrates may be an alternative to intensive ones to sustain ecological processes supporting long-term vegetation growth, as long as there is no net carbon loss. Moreover, broader assessment of decomposition into different green roof substrates configurations could pave the way for a better understanding of green roof ecosystems as a whole and the design of more resilient green infrastructures.

中文翻译：

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用于量化大面积绿色屋顶基质分解率的棉条测定的现场评估

广泛的绿色屋顶 (EGR) 基材和植被层是确保 EGR 多功能性的关键组成部分。然而，人们对 EGR 底物的生物功能知之甚少，尤其是对于维持土壤生命至关重要的养分循环。这项工作旨在首次研究一种经济实惠且易于使用的标准化方法（棉条测定法）的有效性，以评估十年前 EGR 的分解率。将棉条放入基材中孵育 34-110 天后，评估了三个指标：拉伸强度、重量和表面积损失。拉伸强度损失是 34 天后最敏感的指标，而超过 110 天的重量损失证实了与砾石屋顶或普通城市公园土壤相比，EGR 基质的分解率较高。这可能与弱酸性 pH 值和植被覆盖的积极影响有关。最后，只要没有净碳损失，半集约但薄的绿色屋顶基质可能是集约型屋顶基质的替代品，以维持支持长期植被生长的生态过程。此外，对不同绿色屋顶基材配置的分解进行更广泛的评估可以为更好地理解整个绿色屋顶生态系统和设计更具弹性的绿色基础设施铺平道路。