Performance of Two Simulated Green Roofs in the Mediterranean Area

Abstract

The green roofs sector is a relatively recent phenomenon in Mediterranean countries, meaning that as yet there is no complete understanding of which plants are suited to this particular environment. Such plants would need to be adaptable to the green roof itself as well as to the drought and intense lighting typical of a Mediterranean summer. Two simulated green roofs were planted with a variety of species and life forms and subjected to two minimal irrigation treatments and one treatment without irrigation. Mainly subshrub species were planted in one simulation, while the other contained a prevalence of groundcover species. The study looked at performance in terms of species, life forms, and simulation. We analysed flowering, mortality, frequency of planted species and of invasive species, and biomass. We took periodic measurements of cover and of the Shannon-Wiener vegetal diversity index. The groundcover species obtained a higher degree of cover, but suffered more from seasonal stresses. Both green roofs saw an increase in the abundance of a few species, leading to a simplification of the original design. Diversity and the ability to host colonising species were influenced mainly by differences in vegetational structure. Of the subshrub species, Centranthus ruber and Helichrysum stoechas performed best, while Frankenia laevis and Thymus serpyllum came top among groundcover species. In order to withstand severe drought stress, a minimal amount of irrigation was found to be necessary. Our study demonstrates that it is possible to obtain good results from a Mediterranean green roof by using an appropriate combination of vegetal species with different structures and development.

Growth and spread of native perennial herbaceous species on a green roof

“…T. serpyllum, for example, because of its creeping chamaephyte suffruticose habitus, can reduce transpiration (Schulz et al, 2005;Caneva et al, 2015) and more easily tolerate drought. Its use has thus been experimented on green roofs in many Mediterranean areas (Provenzano et al, 2010;Vestrella et al, 2015). At the same time, as indicated by our data during the first period of monitoring, T. serpyllum can develop more quickly than F. ovina, if irrigated, and can sometimes become dominant (Vestrella et al, 2015).…”

“…Its use has thus been experimented on green roofs in many Mediterranean areas (Provenzano et al, 2010;Vestrella et al, 2015). At the same time, as indicated by our data during the first period of monitoring, T. serpyllum can develop more quickly than F. ovina, if irrigated, and can sometimes become dominant (Vestrella et al, 2015).…”

“…These environmental joint values have only recently begun to be considered (Cook-Patton and Bauerle, 2012) in the realization of green roofs, experimenting with plant covers alternative to those most frequently adopted, commonly involving a mixture of Sedum species (Monterusso et al, 2005;MacIvor and Lundholm, 2011;Blanusa et al, 2013;Aronson et al, 2014;Vestrella et al, 2015).…”

Plant Growth on a Mediterranean Green Roof: A Pilot Study on Influence of Substrate Depth, Substrate Composition, and Type of Green Roof

“…For this reason, only relatively recently modern green roofs started being installed in Mediterranean cities. In the same period, scientific interest in designing and establishing Mediterranean green roofs has increased (Benvenuti and Bacci, 2010;Provenzano, 2011;Caneva et al, 2013;Kotsiris et al, 2013;Papafotiou et al, 2013;Raimondo et al, 2015;Vestrella et al, 2015b). Relevant scientific literature has investigated which plants are more suited for Mediterranean green roofs and studies have generally shown that certain plant taxa and xerophytes or succulent plants are the most appropriate for them (e.g., Provenzano, 2011;Papafotiou et al, 2013;Tassoula et al, 2015).…”

Sustainable Growth of Medicinal and Aromatic Mediterranean Plants Growing as Communities in Shallow Substrate Urban Green Roof Systems

“…Based on these multiple requirements, the selection of plant material suitable for extensive green roofs has pointed toward the exploration of native and endemic species adapted to specific areas and climatic zones [1,2,[9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Despite these efforts, there is still a lack of documentation, and a lot of further research is necessary to take advantage of the huge resources offered by native Mediterranean plants in the agricultural, horticultural and landscape industries [23].…”