Assessing Plant Growth Variability and Elevated Substrate Temperatures on Green Roofs Exposed to Excessive Reflective Heat

Abstract Submission: Green roofs have become increasingly important for their benefits in stormwater management, energy conservation, and ecosystem services. However, in densely populated urban areas, green roofs often experience reflective heat and partial shading from nearby buildings, creating severe microclimates that can stress vegetation. Despite these challenges, the effects of these microclimates on plant growth variability across green roofs have not been extensively studied.
This research aims to quantify the uneven distribution of plant growth and the extreme substrate conditions on green roofs subjected to intense sunlight reflection. Using field observations and statistical analysis, we examined a green roof exposed to excessive reflective heat from a building's exterior wall. Over a year, substrate conditions were monitored every 15 minutes with soil sensors, and plant growth metrics were collected monthly. A scoring system was developed to assess plant growth performance.
Our analysis revealed significant differences in substrate temperature, moisture content, and plant growth across the roof. The highest recorded substrate temperature reached 53°C on the hottest day of the year, with a spatial temperature variation of approximately 6°C. Regression analysis indicated a strong correlation between elevated substrate temperatures and reduced plant growth.
These findings highlight the critical impact of reflective heat on plant growth in certain areas of green roofs, emphasizing the need for architects and designers to account for microclimate conditions and consider shading solutions in their designs to enhance plant performance and green roof sustainability.

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