Brownfields and Old-Fields: Vegetation Succession in Post-Industrial Ecosystems of Western New York

Abstract

Post-industrial ecosystems (PIEs) occur where plants and animals spontaneously arrive and establish communities on former industrial sites. There is limited research on these ecosystems compared to other types of abandoned land such as old-fields. A literature review of PIEs and old-fields over the same timeframe and geographic area resulted in >3X more published articles on old-fields than on PIEs. Most old-fields in temperate climates follow a successional pattern of early dominance by herbaceous plants followed by shrubs and trees which develop into a persistent forest ecosystem in the absence of disturbance. Succession of plant communities in PIEs is largely unknown. Observations and theories derived from research in old-fields on plant community succession were compared with field data and aerial photo analysis from a forty-year chronosequence of 20 PIE sites in Erie and Niagara Counties, New York. Based on aerial photo interpretation of vegetation cover on PIE sites and state-transition models, a general successional pattern of a loss in bare ground with an increase in herbaceous vegetation which peaks as it is replaced by a steady increase in woody cover was similar to a conceptual model of old-field succession. Also similar to old-fields, the rate of successional change appeared to slow over time in PIEs, but the years to reach similar levels of woody vegetation cover was slower in PIEs with variability reported in the literature for both PIEs and old-fields. From field data at PIE sites, the dominant species were woody plants with some sites forming a tree canopy of cottonwood (Populus deltoides) and other sites remaining with an open canopy. The overall trend was of increasing shrub cover from the non-native species of Rhamnus cathartica and Lonicera spp., regardless of the successional pathway in the tree layer. A decline of cottonwood and an increase in non-native shrubs suggests a future not of cottonwood forests, but of shrubby thickets of non-native species for PIEs in western New York. Industrial site history was not a factor determining plant communities in the PIE field sites. Site age was a significant predictor of vegetation with an increase in ground vegetation and shrub cover with age. The distance from the 100-year floodplain, a proxy indicator for moisture availability, had the most visible effect on the dominant species shaping the broad vegetation community. The importance of dispersal was also apparent, with high numbers and abundances of species capable of long-distance dispersal, via wind or animals. In general, PIEs follow a similar successional pattern as old-fields, but rates of succession may differ, multiple pathways may occur and species composition may be different in PIEs compared to old-fields.