Anthropogenic sources of toxic elements have had serious ecological and human health impacts. Analysis of the soil samples from a brownfield within Liberty State Park, Jersey City, New Jersey, USA, showed that arsenic, chromium, lead, zinc and vanadium exist at concentrations above those considered ambient for the area. The objectives of the study was to determine if vegetative assemblage distribution on a naturally revegetated urban brownfield was related to soil metal load. In addition, we question wheather the observed difference in soil metal load would alter species trajectories over longer periods of time. The total soil metal load (TML) was calculated as a summation of the rank order transformation of individual soil metals. To estimate the distribution of TML, the data was kriged. To evaluate long term assemblage development trends, historic aerial photographs were digitized and the four guilds, hardwood forest, wetlands, shrub and herbaceous plants were mapped.
Results/Conclusions
A comparison of TML contour map and vegetative assemblage maps indicates that areas of increasing total soil metal load were dominated by successional northern hardwoods while semi-emergent marshes consisting mostly of endemic species were restricted primarily to areas of low soil metal load. An examination of the results indicates that species trajectories in areas where the TML was high favored rapid development of B. populifolia or Populus sp. dominated assemblages. The rapid development of the hardwood assemblage in these areas appears to out-compete herbaceous assemblages and inhibit the development of shrubs. Hence, models for assembly rules, at least those associated with the degraded environments of the urban context, must account for abiotic filters rather than focusing primarily on competition or facilitation between species.
