Herpetofauna Occupancy and Community Composition along a Tidal Swamp Salinity Gradient
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WETLANDS CONSERVATION
Herpetofauna Occupancy and Community Composition along a Tidal Swamp Salinity Gradient S.T. Godfrey 1
&
J.H. Waddle 2
&
R.F. Baldwin 1 & W.H. Conner 3
&
W.C. Bridges Jr 4 & J.A. Duberstein 3
Received: 4 August 2019 / Accepted: 12 December 2019 # Society of Wetland Scientists 2019
Abstract Occupancy patterns of herpetofauna in most tidal freshwater swamps are unknown. Tidal freshwater swamps currently face multiple threats, including salinization, which can influence their associated plant and animal communities. The impacts of salinization to herpetofauna communities in tidal freshwater swamps have not been assessed. To improve predictions regarding these herpetofauna, we conducted surveys in tidal freshwater swamps of the Savannah National Wildlife Refuge located in South Carolina, USA, from March to June, 2016 and 2017, using a variety of methods. Goals included inventorying species, determining communities, examining microhabitat associations, and modeling occupancy to predict the impacts of salinity changes. We detected 8 species of amphibians and 12 species of reptiles in our surveys. Community analyses failed to detect patterns related to measured environmental variables. Species richness and diversity declined along the salinity gradient, but the observed patterns did not match our predictions and may instead be related to site-level heterogeneity. Microhabitat associations were detected for two amphibian species via occupancy analyses. Occupancy and regression analyses indicated soil salinity may be a factor affecting nine species’ occurrences. Amphibian detections may be affected by water depth, pH values, and weather conditions. These results expand our understanding of herpetofauna within an understudied, and threatened, wetland type. Keywords Estuary . Reptiles . Amphibians . Tidal freshwater forested wetlands . Salinity intrusion
Introduction Tidal freshwater forested wetlands (herein referred to as ‘tidal swamps’) are one of the wetland classes that occupy the upper reaches of estuaries, with extent directly related to rates of river discharge (Doyle et al. 2007). Tidal swamps occupy over 200,000 ha of the United States’ coastal areas and range from Maryland to Texas (Field et al. 1991; Doyle et al. 2007). They typically occur in freshwater conditions (< 0.5 practical
* S.T. Godfrey [email protected] 1
Department of Forestry and Environmental Conservation, Clemson University, Clemson, SC 29631, USA
2
United States Geological Survey, Wetland and Aquatic Research Center, Gainesville, FL 32653, USA
3
Baruch Institute of Coastal Ecology and Forest Science, Clemson University, Georgetown, SC 29440, USA
4
Department of Mathematics, Clemson University, Clemson, SC 29634, USA
salinity units (psu)) from the upstream edge of tidal influence to the downstream boundary with oligohaline marsh (0.5 to 4 psu; Odum et al. 1984). Trees in tidal swamps die if exposed to chronic salinity levels of 2 psu or greater, with subsequent conversion to freshwater or brackish marsh oc
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