title: The composition and depth of green roof substrates affect the growth of Silene vulgaris and Lagurus ovatus species and the C and N sequestration under two irrigation conditions.
abstract: Extensive green roofs are used to increase the surface area covered by vegetation in big cities, thereby reducing the urban heat-island effect, promoting CO2 sequestration, and increasing biodiversity and urban-wildlife habitats. In Mediterranean semi-arid regions, the deficiency of water necessitates the use in these roofs of overall native plants which are more adapted to drought than other species. However, such endemic plants have been used scarcely in green roofs. For this purpose, we tested two different substrates with two depths (5 and 10 cm), in order to study their suitability with regard to adequate plant development under Mediterranean conditions. A compost-soil-bricks (CSB) (1:1:3; v:v:v) mixture and another made up of compost and bricks (CB) (1:4; v:v) were arranged in two depths (5 and 10 cm), in cultivation tables. Silene vulgaris (Moench) Garcke and Lagurus ovatus L. seeds were sown in each substrate. These experimental units were subjected, on the one hand, to irrigation at 40% of the registered evapotranspiration values (ET0) and, on the other, to drought conditions, during a nine-month trial. Physichochemical and microbiological substrate characteristics were studied, along with the physiological and nutritional status of the plants. We obtained significantly greater plant coverage in CSB at 10 cm, especially for L. ovatus (80-90%), as well as a better physiological status, especially in S. vulgaris (SPAD values of 50-60), under irrigation, whereas neither species could grow in the absence of water. The carbon and nitrogen fixation by the substrate and the aboveground biomass were also higher in CSB at 10 cm, especially under L. ovatus - in which 1.32 kg C m(-2) and 209 g N m(-2) were fixed throughout the experiment. Besides, the enzymatic and biochemical parameters assayed showed that microbial activity and nutrient cycling, which fulfill a key role for plant development, were higher in CSB. Therefore, irrigation of 40% can maintain an adequate plant cover of both endemic species, particularly in a deeper and soil-containing substrate.
authors.affiliation: Grupo de Enzimología y Biorremediación de Suelos y Residuos Orgánicos, Centro de Edafología y Biología Aplicada del Segura (CEBAS-CSIC), Campus Universitario de Espinardo, Aptdo. de correos 164, Espinardo, 30100 Murcia, Spain. Electronic address: sotovar@cebas.csic.es.
authors.forename: S
authors.initials: S
authors.lastname: Ondoño
authors.affiliation: Departamento de Producción Vegetal, Universidad Politécnica de Cartagena (UPCT), Paseo Alfonso XIII, 48, CP 30203 Cartagena, Murcia, Spain.
authors.forename: J J
authors.initials: JJ
authors.lastname: Martínez-Sánchez
authors.affiliation: Grupo de Enzimología y Biorremediación de Suelos y Residuos Orgánicos, Centro de Edafología y Biología Aplicada del Segura (CEBAS-CSIC), Campus Universitario de Espinardo, Aptdo. de correos 164, Espinardo, 30100 Murcia, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: Moreno
mesh_terms: D044822:Biodiversity; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D002947:Cities; D003247:Conservation of Natural Resources; D055864:Droughts; D009584:Nitrogen / Q000378:metabolism*; D006109:Poaceae / Q000254:growth & development* / Q000378:metabolism; D029751:Silene / Q000254:growth & development* / Q000378:metabolism; D012987:Soil / Q000737:chemistry*
chemical_list: D012987:Soil; D002244:Carbon; D009584:Nitrogen
keywords: Carbon fixation; Compost; Green roofs; Mediterranean semi-arid climate; Microbial activities; Native plant species