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Abstract Green roofs are often used to cool and insulate the buildings below them, but there is a lack of information about optimum design of green roofs to achieve this function in Mediterranean climates. In such climates, the cooling effect of green roofs can also be important on warm days during the winter. In this study, we compared temperatures of non-green roofs, green roofs planted with Sedum sediforme (Jacq.) Pau, and green roofs planted with the same density of Sedum together with annual plants. These plants were chosen because annual plant communities are an important part of semi-arid environments, which are analogous to green roofs. Temperatures were measured below green roof plots and in the substrate. We found that temperatures below green roofs were around 7 °C cooler than below non-green roofs, and that temperatures below Sedum roofs were, in general, 1.5 °C cooler than below annuals + Sedum roofs. The difference in temperatures between green roofs types was seen in summer in the substrate and in winter below the roof. Substrate moisture was higher in Sedum roofs in the summer. Vegetation cover was higher in annuals + Sedum roofs in winter and in Sedum roofs in summer, as Sedum grown alone grew more than Sedum grown with annuals. Overall, Sedum roofs appear to be more effective in providing cooling benefits in this climate, due to higher substrate moisture and vegetation cover in the summer. Thus, to achieve the cooling benefits of an extensive green roof in a Mediterranean climate, it may be prudent to use succulent species alone, without annuals that would compete with Sedum in winter, while not providing a cooling effect in summer. [ABSTRACT FROM AUTHOR]

Green roofs provide many ecosystem services such as regulation of building temperatures, reducing urban heat-island effects and draining rainwater. In addition, they are expected to reduce the high levels of CO 2 concentrations in big cities. Previous CO 2 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 CO 2 reduction, a simple method to quantify CO 2 fixation rate in relation to plant species-composition is required. The method we tested is direct measurement of CO 2 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 CO 2 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 CO 2 concentrations, but only in the absence of Sedum . Sedum alone had no effect on CO 2 concentrations. This emphasizes the importance of integrating plots with annual plants in Sedum -based green roofs. [ABSTRACT FROM AUTHOR]

Abstract: Green roof research is a multidisciplinary and new research area. We conducted a bibliometric quantification to assess the rate of publications in specific areas of research for this novel research area based on the scientific literature as available from the Web of Science. Bibliometric research can provide valuable information about changes in the trends within a particular area of research. For example, we found that the number of publications in this field increased in the last two decades at very similar pace to other pre-established academic disciplines. We also found that papers on green roofs were classified into 32 research areas. There was very little change in the frequency of most research areas through time. The percentages of plant sciences, forestry, marine and freshwater biology and biodiversity conservation of the total research areas classifications used each year increased significantly with time, while architecture decreased significantly with time signifying an increased interest in environmental issues and less focus on architectural issues. The distribution of publications between countries has been skewed, with the USA and the EU conducting 66% of the research, and thus allocation of research effort is focused in those continents and predominantly in temperate ecosystems. However, there has been a sharp increase in the number of countries that conduct green roof research. Our work provides a suite of indicators that can be combined to give a useful picture of the development of green roof research and identifies the challenges which lie ahead for this novel research area. [Copyright &y& Elsevier]