title: Spatially dependent biotic and abiotic factors drive survivorship and physical structure of green roof vegetation.
abstract: Plant survivorship depends on biotic and abiotic factors that vary at local and regional scales. This survivorship, in turn, has cascading effects on community composition and the physical structure of vegetation. Survivorship of native plant species is variable among populations planted in environmentally stressful habitats like urban roofs, but the degree to which factors at different spatial scales affect survivorship in urban systems is not well understood. We evaluated the effects of biotic and abiotic factors on survivorship, composition, and physical structure of two native perennial species assemblages, one characterized by a mixture of C4grasses and forbs (Hempstead Plains, HP) and one characterized by a mixture of C3grasses and forbs (Rocky Summit, RS), that were initially sown at equal ratios of growth forms (5:1:4; grass, N-fixing forb and non-N-fixing forb) in replicate 2-m2plots planted on 10 roofs in New York City (New York, USA). Of 24 000 installed plants, 40% survived 23 months after planting. Within-roof factors explained 71% of variation in survivorship, with biotic (species identity and assemblage) factors accounting for 54% of the overall variation, and abiotic (growing medium depth and plot location) factors explaining 17% of the variation. Among-roof factors explained 29% of variation in survivorship and increased solar radiation correlated with decreased survivorship. While growing medium properties (pH, nutrients, metals) differed among roofs there was no correlation with survivorship. Percent cover and sward height increased with increasing survivorship. At low survivorship, cover of the HP assemblage was greater compared to the RS assemblage. Sward height of the HP assemblage was about two times greater compared to the RS assemblage. These results highlight the effects of local biotic and regional abiotic drivers on community composition and physical structure of green roof vegetation. As a result, initial green roof plant composition and roof microclimate may have long-term effects on community dynamics, ecosystem function, and urban biodiversity.
authors.affiliation: Louis Calder Center, Biological Field Station, Department of Biological Sciences and Center for Urban Ecology, Fordham University, P.O. Box 887, Armonk, New York, 10504, USA.|Wildlife Conservation Society, 2300 Southern Boulevard, Bronx, New York, 10460, USA.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Aloisio
authors.affiliation: Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, New York, 10027, USA.
authors.forename: Matthew I
authors.initials: MI
authors.lastname: Palmer
authors.affiliation: Wildlife Conservation Society, 2300 Southern Boulevard, Bronx, New York, 10460, USA.|Department of Urban Studies and Planning, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA.
authors.forename: Mario A
authors.initials: MA
authors.lastname: Giampieri
authors.affiliation: PSEG Institute for Sustainability Studies, Montclair State University, 1 Normal Avenue, Montclair, New Jersey, 07043, USA.
authors.forename: Amy R
authors.initials: AR
authors.lastname: Tuininga
authors.affiliation: Louis Calder Center, Biological Field Station, Department of Biological Sciences and Center for Urban Ecology, Fordham University, P.O. Box 887, Armonk, New York, 10504, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Lewis
mesh_terms: D058448:Biota; D003247:Conservation of Natural Resources; D005160:Facility Design and Construction; D008136:Longevity; D009519:New York City; D063245:Plant Development; D018521:Plant Physiological Phenomena
keywords: biodiversity conservation; community; green infrastructure; green roof; survivorship; sustainability; urban ecology; urbanization; vegetation