Life on the rocks: Small-scale primary succession in an abandoned limestone quarry

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Sophia Atkinson, Diana Borse, Cedrick Chandler, Daniel L. Saltz and Dana A. Dudle, Biology, DePauw University, Greencastle, IN

Background/Question/Methods
Abandoned quarries, from which all soil and plant life have been removed, represent an opportunity to study primary succession at a small scale. Recent studies of highly damaged landscapes such as hard-rock quarries of France and fly-ash deposits in Central Europe suggest that abandoned mines can sometimes provide refuge habitat for native plant species of conservation concern. Using a framework suggested by Gilardelli et al. (2016) we assessed the stage of primary succession in an abandoned limestone quarry in Greencastle, Indiana, where gravel extraction ceased in 1977. From 2018-2021 we surveyed the quarry floor to describe the species composition and distribution of flowering plant species that have established at the site, then described each species in terms of its plant form, life history, native and wetland status, and invasive rank using the USDA website. We characterized the substrate and identified several microhabitats within the quarry, to determine which conditions are conducive to hosting diverse assemblages of native species.
Results/Conclusions
Surveys from 2018-2020 revealed populations of 98 flowering plant species established on the quarry floor, 73% of which are native to the region. Of the 27 non-native species, seven have been identified as highly invasive. The majority of the species we identified are herbaceous in plant form and have perennial life history. Nineteen species are classified as facultative or obligate wetland species. We described several distinct sub-habitats within the quarry including spoil heaps, talus slopes, dry and wet limestone flats, and temporary ponds which vary significantly in species composition, substrate texture and water availability. Talus slopes host the highest diversity of shrubs, and limestone flats at low elevation host the highest proportion of wetland species.
According to Gilardelli et al. (2016), limestone quarries in late-phase succession are dominated by perennials; also, shrubs tend to replace herbaceous plants in later phases of succession. Although we found that that most of the species currently growing in the Nature Park quarry are native, herbaceous perennials, we have not yet quantified the relative abundance and percent cover of these species on the quarry floor. Preliminary analysis suggests that succession in the quarry proceeds at variable rates depending on substrate and water availability.