Micro-scale ecosystem differentiation and pollination network of the extensive green roof of the Terra Research Center

Abstract

Green roofs are often praised for their contribution to supporting biodiversity. However, their ecological performance depends on their design and environmental conditions. This work addresses various ecological components of the roof of the TERRA building, three years after its installation. It focuses on two themes. The first one addresses the differentiation of the ecosystem over time according to the depth of the substrate and the amount of sunlight received. Functional and taxonomic approaches revealed that the interannual variation in the plant communities of the roof was greater than the variations caused by substrate depth and sunlight. Over time, the communities evolved towards a more competitive and less stress-tolerant strategy. The analysis of the LHS traits suggested a community response to climatic events, particularly to the drought of spring 2020. After three years, a slight differentiation of substrates according to micro-environmental conditions was observed but was not the origin of the differentiation of plant communities. The second theme focuses on the plant-pollinator network of the roof. The results show a low species diversity of pollinators, including only generalist pollinators. The evolution of insect captures and of the presence of flowering species within the quadrats suggests that greater plant abundance and diversity are needed to ensure the continuous delivery of floral resources to pollinators. These two themes provide knowledge about the actual performances of the roof of the TERRA building and suggest the need for further research on the long-term resilience of green roof plant communities.