Ephemeral wetlands, categorized for their inundation during the spring followed by drying in the summer, are critical habitats for several endemic species, including some amphibians and macroinvertebrates. These pools may provide safe-havens for certain organisms such as juvenile amphibians. Very little is known about the habitat conditions of the pools in the Indiana Dunes National Park. We collected baseline data on the floral characteristics of ephemeral wetlands within the Cowles Bog unit of the park. After obtaining baseline data, long-term monitoring of these characteristics would provide information on how these vernal pools may respond to climate change.
Thirty-one vernal pools have been identified previously in 2018. Data collection occurred during the summer of 2019. Ground cover of herbaceous species, as well as the density and basal area of woody species and trees, were determined in a total of ninety-nine plots (9 m2 for herbs and woody species and 30 m2 for trees) along the shoreline of eight pools. Importance value of each species was calculated. Species richness and species diversity were calculated for all pools. Canopy cover was measured in each plot. To examine similarities and dissimilarities among the plots, a data matrix of the importance value was subjected to non-metric multidimensional scaling ordination (NMS).
Results/Conclusions
Ninety-nine species were identified along eight ephemeral pools between two separate clusters (cluster 1 and cluster 4). Mean tree canopy was 84% in cluster 1 and 72% in cluster 4. Herbaceous species showed significant differences in total cover, species richness, species diversity, and species importance value. Characteristic ground flora consisted of virginia creeper (Parthenocissus quinquefolia) and threeleaf goldthread (Coptis groenlandica) in cluster 1, and hog peanut (Amphicarpaea bracteata) and Indiangrass (Sorghastrum nutans) in cluster 4. Woody species showed differences between clusters 1 and 4 in terms of both species richness and diversity, while both trees and woody species showed differences between mean basal area and mean density. Dominant species consisted of red maple (Acer rubrum), sour gum (Nyssa sylvatica) and black cherry (Prunus serotina) in cluster 1, as well as white oak (Quercus alba), sassafras (Sassafras albidum) and Rubus species in cluster 4. The occurrence of nineteen exotic species was not significant at this time but suggests an early stage of invasion. We hypothesize that successional and light exposure gradients were responsible for the vegetation dissimilarity between cluster 1and 4.