One hallmark of the urbanization process is the significant alteration of soil either through the intense modification of natural soils or through the creation of novel, anthropogenic soils through activities such as dumping waste material. Given the unique properties of such soils and their ubiquity in the urban landscape, it is necessary to understand how these highly altered soils may influence patterns of community development and biodiversity. The objective of this study was to assess changes over time in plant diversity and composition in a highly altered landscape as well as to assess the role of soil properties on assemblage composition. The study site is located in Jersey City, New Jersey at an urban brownfield with heavy metal contaminated anthropogenic soil. Its plant community is entirely volunteer vegetation which presumably began to establish around 1970. We studied 29 permanent plots spread throughout the site representing four assemblage types: grassland (5 plots), forb-herb (10), shrubland (5) and forest (9). Within each plot, we identified individual species and estimated their total cover in 2008 and 2016 (approximately 38 and 46 years post-establishment). We collected soil samples from each plot in 2008 and analyzed them for a suite of physical and chemical properties.
Results/Conclusions
Non-metric multidimensional scaling (NMDS) analysis and a permutation based ANOVA showed distinct community composition within each assemblage type, though site-wide community composition did not change during the study period. Species richness and diversity significantly increased from 2008 to 2016, regardless of assemblage type. Plots which had comparatively lower heavy metal concentrations tended to add more species during the study period while plots with higher metal levels added fewer species. A comparison between the NMDS plot and soil properties suggests that in 2008 forb-herb plots tended to be located in soils with higher nutrient levels while forest and shrubland plots tended to be in soils with higher levels of heavy metals and deeper soils. Forest plots tended to have the highest richness and Shannon Index. Though within forest plots, the proportion of cover contributed by tree species decreased over time, potentially resulting from damage from Hurricane Sandy or other causes of dieback. The spatial variability of properties in this site’s anthropogenic soil has enabled multiple assemblage types to establish, contributing to the site’s plant diversity and richness. Notably site richness and diversity have continued to increase in the past 8 years in spite having been abandoned over 40 years ago.