One way to maximize the eco-friendly factor of a structure is to include a green roof—and this doesn't refer to the paint color. "Greening" a roof, or covering a roof with vegetation, is gaining popularity in North America, where the number of green roofs increased 30% from 2006 to 2007.
Benefits of green roofs include improved storm water management, energy conservation, reduced noise and air pollution, improved biodiversity, and even a better return on investment than traditional roofing.
But a healthy roof requires the selection of a species that can survive extreme climates and propagate easily to reduce erosion and weed growth. Kristin L. Getter of Michigan State University's Department of Horticulture led a study to determine the effect of the growing medium's depth on the success of green roofs. The research study, published in a recent issue of HortScience, focused on Sedum, a variety of succulent known for its drought tolerance.
Plots were constructed using the drainage mats and waterproofing systems typical of green roofs, but the growing material varied in depth from 4 cm, 7 cm, and 10 cm. Twelve species of Sedum were planted, fertilized, and watered once. The moisture of the growing material was measured at random times each week. Measurements of chlorophyll fluorescence were taken to monitor the health of the plants during a variety of environmental conditions.
Plants were monitored over the course of four years. Since the average lifespan of the inorganic components of a green roof is about 45 years, the researchers determined that it was important to study the longevity of the plants. The study found that the shallowest plot had the lowest moisture levels on average and dried the fastest after a rain. At the 4-cm depth, four species failed to exhibit significant growth over the 4-year period.
Five species showed no or little growth at the 7-cm depth, and six species showed no or little growth at a depth of 10 cm. Some species declined over the 4-year period at the varying depths. The remaining plants that flourished were the same species for all three depths (S. floriferum, S. sexangulare, S. spurium 'John Creech', and S. stefco). The 4-cm depth also included two other species (S. hispanicum and S. reflexum 'Blue Spruce').
Furthermore, the results indicate that, for the surviving and most-abundant species, there is no benefit to depths greater than 7 cm, which would appear to be good news considering shallow depths are more desirable because they make for lighter roof loads. "However, at deeper depths, these plants would likely be healthier, contain greater biomass, and be less susceptible to adverse environmental conditions. This study shows the importance of growing medium depth for plant performance and demonstrates the need for long-term evaluation of species for use in this green practice", concluded the researchers.
The complete study and abstract are available on the ASHS Hortscience electronic journal web site: http://hortsci.ashspublications.org/cgi/content/abstract/44/2/401
Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application.
Michael W. Neff | EurekAlert!
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
19.02.2018 | Materials Sciences
19.02.2018 | Materials Sciences
19.02.2018 | Life Sciences