Comparing brownfield and old-field floras of New Jersey: Do non-native plants make up a higher proportion of brownfield floras?

Background/Question/Methods

Plants that grow in urban and post-industrial areas need to cope with conditions that are by-products of intense human activities. Urban brownfields are sites characterized by high levels of industrial by-products: hazardous substances, pollutants, or contaminants. Old fields, in contrast, are abandoned agricultural fields; they are also created by humans, but typically do not have significant soil contamination. Due to a difference in industrialization timeline between Europe and North America, plants native to Europe may be better adapted to environmental conditions created by industrialization present in urban brownfields. To explore the hypothesis that some non-native plant species are pre-adapted to urban brownfield environments while both native and invasive plant species are adapted to old-field conditions, we have sampled vegetation at five brownfield and five old-field sites located in central and northern regions of New Jersey. At each site, we used three Whittaker plots along a 100 meter transect to sample vegetation in the late summer of 2012. Within each quadrat and plot sampled, we recorded percent cover of each species and cover type.

Results/Conclusions

The recorded vegetation sampling data varied considerably between sites. This is likely due to different site histories and locations. The species richness for old-field sites ranged between 24 and 48 recorded species. Species richness ranged similarly from 24 to 42 for the brownfield sites. Three out of five old-field sites had over fifty percent native species out of all recorded species. Only one brownfield site had over fifty percent native species. The brownfield site with a high percentage of native species does not have a high total number of native species because it had one of the two lowest total number of species (24) out of all sites and is dominated by a single non-native species (Artemesia vulgaris). The two old-field sites with lower percentages of native species also had lower total species richness values of 29 and 24. These results support the hypothesis that more non-native species are pre-adapted to brownfield conditions. Further directions include analysis of soil samples and consideration of other site characteristics including surrounding landscape composition. These results will also serve as the basis for further research including field transplant and greenhouse experiments using the most common native and non-native species in the surveys.