The influences of canopy cover and carbon inputs on the biodiversity of vernal pools

Background/Question/Methods   Vernal pools are critically important habitats for many species of amphibians, invertebrates, and plants, such that one pool may have greater species diversity than the entire surrounding upland. Although the amphibian communities are widely studied, the macroinvertebrate communities are often ignored despite their roles in ecosystem cycling both within pools and between the surrounding landscape. Hydroperiod and water quality are often considered the dominant factors controlling macroinvertebrate biodiversity. However, recent inferences from stream ecology have also implicated that canopy cover and carbon inputs can regulate resource quantity and quality in these temporary wetlands. Northwest Ohio offers a unique opportunity to study how ecological controls affect invertebrate biodiversity, as it contains a variety of vernal pools among its forest and savanna habitats. Thus, we sought to determine how canopy cover and carbon sources influence macroinvertebrate biodiversity in 15 vernal pools, hypothesizing that open canopy pools support a greater diversity of macrophytes, algae, and macroinvertebrates.

Results/Conclusions   5,400 macroinvertebrates from 31 taxonomic families were collected in this study. Fingernail clams (Sphaeriidae) and clam shrimp (Lynceidae) represented 48% of these invertebrates but were only present in half of the pools. Macrophyte abundance tended to increase with canopy cover and consisted largely of buttonbush (Cephalanthus occidentalis), sedges (Carex spp.), and ferns. Multiple regression reveals that canopy cover and pool area account for 67% of the variation in macroinvertebrate biodiversity, while pool depth, litter quality, and water quality were unimportant. Most likely, larger pools have more habitats to support more invertebrates, while open tree canopies may allow for a greater diversity of macrophytes and algae, which provide both shelter and food resources for macroinvertebrates. Initial analyses of water quality among these vernal pools suggest water chemistry may have been too invariant to affect macroinvertebrate biodiversity. Further analyses of nitrogen, phosphorous, and phenolic content may help explain additional variation in the patterns of local macroinvertebrate biodiversity.