Across urban-rural gradients, site legacy, site availability, species availability, and species performance affect vegetation dynamics. The confluence of altered disturbance regimes, biophysical processes and invasive species as well as social contexts and anthropogenic influences create an novel environment in the urban landscape as compared to rural landscapes resulting in unique species distributions, abundances, and functional traits as well as community assemblages in forest patches.
Tree species data from New York, New York; Syracuse, New York; and Tampa Bay, Florida illustrate how species patterns vary across urban-rural gradients and the influence of site legacy. Site legacy is defined by two classes: sites with forest cover pre-1940 (remnant) or sites that developed forest cover post-1940 (emergent).
In the urban landscape, we observe species shifts with legacy playing an important role. Remnant-upland sites are shifting from long-lived species, such as Quercus and Carya spp., to short-lived species such as Prunus spp. and Betula spp. Emergent-upland sites are dominated by native and non-native short-lived species that are predominantly anemonochory dispersed. In rural landscapes, no similar species shifts are observed for remnant sites, and emergent sites are dominated only by native species with anemonochory and zoochary dispersal. Unlike emergent-upland sites, emergent-wetland sites are structurally and compositionally similar to remnant wetland sites. No data are available on species shifts for remnant-wetland sites. Overall, these shifts for upland sites, do not imply a species debt, but rather shifts in their importance or contribution to the overall forest structure and resulting functions.