AMPHIBIAN USE OF RESTORED WETLANDS OF DIFFERENT AGES
thesisposted on 20.12.2021, 15:28 by Patrick James RansbottomPatrick James Ransbottom
Wetland-dwelling amphibians are of conservation interest for numerous reasons. They serve as biological indicators of water quality during their fully aquatic larval phase, and as carnivores that prey extensively on both terrestrial and aquatic invertebrates. These amphibians are an important link between terrestrial and aquatic food webs, and their wellbeing is an important factor when considering ecosystem health. Amphibians are facing global declines as their wetland habitats are being lost or degraded by human actions. There are efforts to restore wetland habitats, but it is far from certain which practices encourage amphibian occupancy.
I investigated which factors are important to the persistence of amphibians in restored and naturally formed wetlands to see if restored wetlands can accommodate similar species assemblages. Amphibians were surveyed over two years in a collection of 18 wetlands in Steuben and DeKalb counties, IN owned by The Nature Conservancy. Ambystomatid salamanders were surveyed using plastic minnow traps in springtime, and frogs were surveyed using call surveys in spring and summer. I used linear models to compare wetland plant dominance, wetland hydroperiod, restoration status, distance to nearest mature forest, adjacent forest age and basal area, and inter-wetland distance to amphibian species richness.
The species richness of Ambystoma salamanders was positively associated with larger wetlands, higher forest basal area, and central mudminnow presence; and negatively associated with older forests, distance to mature forests, and the presence of sunfishes. Ambystoma salamanders besides A. tigrinum were associated with ephemeral hydrology, naturally-formed wetlands, and a greater number of wetlands within one km; and negatively correlated with older forests.
Frog species richness was positively associated with larger wetland size, and negatively associated with seasonal wetlands, naturally-formed wetlands, distance to nearest mature forests, naturally formed wetlands, treatment for invasive plants, and number of other wetlands within 500m. Total amphibian species richness models did not perform well, but showed a preference for semi-permanent wetlands, smaller distance to mature forests, greater forest basal area, and greater distance between wetlands; and a preference against Scrub Shrub/Forest wetlands. Hylid frogs were negatively correlated with naturally formed wetlands. Ranid frogs were associated semi-permanent wetlands and negatively correlated with the number of other wetlands within 500 m.
Ambystomatid salamanders were found in restored wetlands, semi-permanent wetlands, and in wetlands containing central mudminnows. Frogs may dislike the disturbance from removing invasive grasses. Managers should factor the disparate habitat requirements of amphibian taxa into their plans for creating and managing restoration projects. Different amphibian groups appear to differ greatly in their habitat requirements, and diverse wetlands may enhance the species richness of an area. Skillfully restored wetlands appear to serve similar functions to original, naturally formed ones.