The effect of soil depth heterogeneity on species diversity, biomass, and weedy species colonization on an extensive green roof (Amy Heim)
Currently, the majority of extensive green roofs are planted solely with species from the genus Sedum. These plants are extremely drought tolerant but are not as efficient at providing ecosystem services as other potential green roof vegetation. For example, taller species with wider leaves are more efficient at reducing storm water runoff and substrate temperatures than the short succulent Sedum species. However, this does not necessarily mean that Sedum should be excluded from green roof vegetation. Research has demonstrated that biodiverse green roofs, containing a mixture of growth forms, may improve overall green roof function. This three-year study examined how soil depth heterogeneity may increase plant diversity and increase biomass on extensive green roofs. This study was composed of three homogenous soil depth treatments (15, 10 and 5 cm) and one heterogeneous treatment (soil depth varied between 5 and 15 cm). Each treatment was planted with 20 different species, and measurements for species diversity and plant biomass were collected. Overall, soil depth heterogeneity resulted in an overall increase in plant biomass, compared to the homogenous treatment containing the same quantity of soil (10 cm treatment). However, for plant diversity and weedy species colonization, little difference was observed between these two treatments. More time is necessary to see if the trends observed continue in the future.
Amy Heim won an ISHS student award for the best poster at the International Symposium on Greener Cities for More Efficient Ecosystem Services in a Climate Changing World in Italy in September 2017.
Amy Heim, Saint Mary’s University, 923 Robie Street, Halifax, B3H 3C3, Nova Scotia, Canada, e-mail: email@example.com
The full article is available in Chronica Horticulturae