GIS-based analysis to understand the effects of environmental variability on the growth and success of native plants on green roofs

Abstract

Green roofs have a number of realized benefits including reducing stormwater runoff, saving building energy costs, and reducing the urban heat island effect. However, more research is needed to understand the effects of environmental variability on plants growing in these dynamic systems. In this study, Geographic Information Systems were used in conjunction with statistical analysis to uncover some of these relationships. 69 Sibbaldiopsis tridentata plants and 72 Solidago bicolor plants were monitored across an extensive green roof located in Halifax, Nova Scotia, from June 5th to November 10th, 2014. Plants were measured based on growth, survival, and reproductive potential and environmental data were also collected. Spatial information was obtained from the plants by turning the roof into a grid system. Additionally, a 3D model of the roof was constructed in ArcGIS. The model was then used in GIS to calculate a solar radiation model of the roof surface and this was incorporated into the analysis. Both species achieved faster growth, but had a greater risk of mortality, where there was low cover of vascular plants. Plant growth and survival were also greater with higher soil moisture, lower soil temperatures, and deeper soil. There were also species differences in responses to environmental conditions. The data show that significant spatial environmental variability occurred across the green roof system. Furthermore, certain building features, such as the Atrium Triangle, created detectable microclimates that influenced many plant and environmental variables. The data suggest that these microclimates were beneficial for plants growing on the extensive green roof. Geographic Information Systems not only provided the ability to visualize important spatial relationships but it also contributed significantly to the data analysis and ultimately to an increased understanding of the dynamic nature of the green roof system.