Identification of environmental drivers in urban greenway communities

Abstract

Urban trails and greenspaces have become ubiquitous features in cities, in part due to their ability to provide ecological benefits to the built-up environment. A major factor in their popularity is their potential to enhance habitat connectivity by bridging the gaps between remnant patches across urbanized areas, however, information on the structure and function of greenways themselves is limited. In this study we examined how greenways serve as distinct habitats in their own right by characterizing the vegetative structure of the Capital Area Greenway (CAG) in Raleigh, NC. We conducted a systematic vegetation survey of woody vegetation along 39 km of trails (354 random plots) in 2016 and identified environmental variables related to site conditions (percent canopy cover, stream proximity, flood zones), management efforts (designated conservation areas), and local anthropogenic activities (percent impervious surface, street proximity). We preformed three types of multivariate analyses (non-metric multidimensional scaling (NMS), multi-response permutation procedures (MRPP), and indicator species analysis (ISA)) to distinguish potential influences on species distribution and community structure. We observed highly diverse riparian, upland mesic, and xeric forest communities within the CAG. Results from NMS and MRPP suggested that vegetation patterns can be differentiated based on local environmental variables. Sites located in conservation areas and floodplains, for instance, were typically found at further distances from streets and were characterized by greater basal area, canopy cover, and higher non-native species richness. Individual study sites were highly diverse and varied even within similar local environments. Our findings indicate that the CAG serves as established natural habitat for native vegetation, supporting the idea that greenways can be used to enhance environmental quality in cities as ecological corridors.