Plant community dynamics in a peri-urban central Indiana flatwoods between 1996 and 2007

Background/Question/Methods

Nature preserves in urban and peri-urban settings face all of the challenges to maintenance of ecological integrity that preserves in wildland settings do.  Habitat fragmentation, edge effects, and invasive species in both locales can contribute to habitat degradation and erosion of biodiversity.  These effects can be exacerbated in and near cities where close proximity to the built environment can lead to greater opportunity for certain types of human-related disturbance, including escape of invasive exotic ornamental species from landscaping into preserves.  One way to monitor and quantify changes in ecological integrity is to track structural and compositional changes in vegetation through time using permanent plots.  We used permanent plots to sample herb-layer vegetation in a state-dedicated nature preserve located within a large city park in Indianapolis, Indiana, in the Midwestern USA.  Plots were established and sampled in 1996 and resampled in 2007.  In order to assess the possible role of contiguous woodlands in the large park that are outside the boundaries of the nature preserve as sources of ecological disturbance, we also sampled plots located in a 100 m buffer of forest outside the preserve.  This buffer area does not receive the same degree of stewardship effort as the nature preserve proper.                

Results/Conclusions

A total of 134 species were recorded during the two inventory years.  Most were native, including all plants seen in plots inside the preserve at the beginning of the study.  There were no differences between vegetation structure (species richness, evenness, or diversity) and no differences in floristic quality assessment metrics between years.  For 2007, but not 1996, inside plots had higher mean native C values with non-natives and higher FQI values than plots located outside the preserve.  There was considerable species turnover between years.  Jacard’s matching coefficents were only 0.43 for plants in plots located inside the preserve for the two sample years and 0.44 for plants in plots outside the preserve.  The largest difference was found for perennial forbs, with over 50% more species coming or going during the 11 years between surveys than remaining present.  Most species that turned over between sample years had low relative importance values.  Four of the five invasive non-native species present in the preserve by 2007 were found in adjacent sample plots outside the preserve in 1996.  Our results show that buffer areas around the preserve are an apparent source and early warning of species that may become management problems.