Post-industrial ecosystems (PIEs) occur on abandoned industrial sites; old-fields occur on abandoned agricultural lands. While old-fields have been extensively studied, PIEs have not and provide an interesting comparison with old-fields and unique sites for research in urban ecology. Old-fields in temperate climates follow a general successional pathway of rapid colonization of bare ground by herbaceous plants followed by woody plants which develop into a persistent woodland or forest ecosystem in the absence of disturbance. As old-fields progress along this general pathway, the rate of successional change has also been observed to slow over time. Pathways and rates of succession in PIEs are unknown and may differ from those in old-fields due to the differences between agricultural and industrial disturbances, the extreme soil conditions in PIEs, or differences between an urban and rural species pool and the traits of those species. We compared the successional pathways and rates of succession in PIEs to old-fields. We built state-transition modes of PIE succession from aerial photo interpretation of bare, herbaceous and woody cover in 3 to 12 year time series of photos using a forty-year chronosequence of twenty PIE sites. An age-dependent model with unique transition matrices at three-year intervals was developed, as well as a model with one transition matrix averaged across all site ages. These models were compared to a conceptual model of old-field succession developed from the old-field literature, as well as to the number of years to reach levels of woody cover establishment reported in old-fields.
Results/Conclusions
In both PIEs and old-fields, the initial years following abandonment are associated with a rapid increase in herbaceous vegetation as bare ground is colonized. This is followed by a peak in herbaceous cover with a steady increase in woody plant cover. However, PIEs did not reach 10% or 50% woody cover as fast as old-fields. The age-dependent PIE model did reach 10% woody cover within the range reported in old-fields which reflects the faster rate of succession at younger ages which has also been reported in old-fields. The similarity in the general pathway of succession in PIEs and old-fields suggests factors such as abiotic filters, species dispersal traits, and competitive interactions result in similar ecosystem types. However, succession in PIEs appears to be slower than in old-fields. Differences in species composition and successional pathways over a longer time frame may still occur between PIEs and old-fields.