Adaptability of different plant species on an extensive green roof

Abstract

Plant species used on green roofs in Brazil are of predominantly exotic origin, which is at variance with the diversity of plants available naturally in the country. This study aims to evaluate the development and adaptation of different species of the flora of the state of Rio Grande do Sul, Brazil, using the extensive green roof system in the presence and absence of irrigation. Eight treatments were carried out using three species native (Alternanthera hirtula, Angelonia integerrima and Dyckia hebdingii) and one exotic species (Aptenia cordifolia), which had their development evaluated in the presence and absence of irrigation. Monthly evaluations were carried out over twelve months to assess height, vegetation cover, maintenance of aerial vegetation, visual aspect of plants, shoot dry matter, and root dry matter. For Dyckia hebdingii and Aptenia cordifolia, the height showed a linear growth independent from the irrigation regime and a decrease in temperature in colder seasons. A. hirtula and A. integralerrima presented oscillation in height increase influenced by environmental temperature conditions. The same behavior was observed for vegetation cover. For most of the time, all species maintained an adequate visual aspect, except for the period when A. hirtula and A. integerrima entered senescence. For shoot and root dry matter, only A. hirtula showed higher values when irrigated among the native species tested. It is concluded that the different species of native flora of the state of Rio Grande do Sul tested have a potential for use on extensive green roofs without the need for irrigation under the conditions in which the present work was developed.