| Environmental calcium is an important but often overlooked factor in invertebrate community studies. The amount of calcium in upper soil horizons is primarily influenced by mineral content of bedrock parent material, nutrient input via leaf fall from vegetation, and anthropogenic factors including acid precipitation and forestry management practices. Because it is needed for reproduction and shell formation, calcium is an important nutrient for land snails. Soil calcium varies across the landscape and can influence land snail distributions. I found that land snail density and diversity were highly correlated with O-horizon soil calcium levels in the Jocassee Gorges region of northwestern South Carolina. Isolated sites within this region exhibit unusually high land snail diversity because of the presence of the Chauga geological belt which weathers to produce very high calcium, high pH soils. There was not a corresponding positive correlation between land snail diversity and malacophagous cychrine beetle diversity as predicted by bottom-up theories of community structure. Cychrine diversity was positively correlated with elevation, independent of soil calcium, for two species, Scaphinotus viduus (Dejean) and Sphaeroderus stenostomus lecontei (Dejean), which were found only above 750 meters. In a separate study, the experimental addition of lime significantly raised land snail density in a mixed hardwood forest. Despite efforts to address the question, it is still unclear if increases were due to immigration from outside of treated areas or increased reproduction within them. In another study, O-horizon soil calcium and land snail density and diversity were higher underneath the canopies of flowering dogwood ( Cornus florida), a species known for high leaf calcium content. Because land snails are important food sources for a variety of organisms including birds, insects, and salamanders, the threat of dogwood anthracnose fungus (Discula destructiva) may reach beyond the target species. Finally, I found that the use of barrier-connected pitfall traps significantly increased the number of land snail specimens and species detected at individual sites when used in conjunction with traditional sampling methods, namely litter sieving and timed searching. Their ubiquity, diversity, and ease of sampling make land snails an attractive focal group for community ecology and conservation research. |
