The Influence of Flowering Dogwood (Cornus florida) on Land Snail Diversity in a Southern Mixed Hardwood Forest

Abstract

In many areas, soil calcium is an important limiting factor for land snail distributions. Some tree species are able to extract calcium from lower soil depths, concentrate it in their leaves and deliver it to the surface upon leaf fall. Flowering dogwood (Cornus florida) is an example of a “calcium-pumping” species and has been suggested to promote land snail diversity in woodland ecosystems. In this study, leaf tissue calcium, O- and B-horizon soil calcium and land snail diversity were compared for three common understory tree species: flowering dogwood, American beech (Fagus grandifolia) and blackgum (Nyssa sylvatica). Using a litter sieving technique, land snails were sampled underneath these three focal tree species. Land snail density, species richness and diversity were estimated for a total of 19 trees. As expected, B-horizon soil calcium was similar across all tree species, while leaf tissue calcium and O-horizon soil calcium were significantly higher for flowering dogwood. Land snail density, species richness and diversity (Shannon-Wiener Index) were also significantly higher for flowering dogwood. Calcium-pumping tree species are important ecosystem components in that they increase soil fertility and promote invertebrate diversity. Land snails are an important food and calcium source for a variety of woodland species including passerine birds, woodland salamanders, cychrine beetles, and wild turkeys. Flowering dogwood is currently seriously threatened in the southeastern United States by the parasitic dogwood anthracnose fungus (Discula destructiva). In light of the findings of this study, the implications of dogwood anthracnose may reach beyond the target species and impact multiple taxa.