Measuring the effect of plant-community composition on carbon fixation on green roofs

By: Agra H., Klein T., Vasl A., Kadas G., Blaustein L.
Published in: Urban Forestry and Urban Greening
SDGs : SDG 11  |  Units:   | Time: 2017 |  Link
Description: Green roofs provide many ecosystem services such as regulation of building temperatures, reducing urban heat-island effe cts and draining rainwater. In addition, they are expected to reduce the high levels of CO2 concentrations in big cities. Previous CO2 fixation studies on green roofs were done by taking long-time-period samples using expensive equipment and with limited replication. To plan green roofs for optimal CO2 reduction, a simple method to quantify CO2 fixation rate in relation to plant species-composition is required. The method we tested is direct measurement of CO2 concentrations with a portable air-quality meter, which allows a large number of samples. Here we focus on differences in the photosynthetic effect between plots containing the local Mediterranean succulent, Sedum sediforme and plots containing various annuals. In a factorial design (presence or absence of Sedum crossed with presence or absence of annuals), we tested the effect of sedum and annual treatments on CO2 concentrations. To compare our results with a commonly used method, and to evaluate the role of the different species, we examined the photosynthetic activity at the single plant level under these treatments by using a portable gas-exchange measuring system. We found that our method can detect the effect of different green roof plots and can be used as a simple and reliable tool for green-roof planers. We found that annuals reduced CO2 concentrations, but only in the absence of Sedum. Sedum alone had no effect on CO2 concentrations. This emphasizes the importance of integrating plots with annual plants in Sedum-based green roofs. © 2017 Elsevier GmbH