Landscape metrics as predictors of hydrologic connectivity between Coastal Plain forested wetlands and streams.

Steven M Epting,Alec W Armstrong,Laurie C Alexander,Margaret A Palmer,Jacob D Hosen,Megan W Lang

doi:10.1002/hyp.11433

Abstract

Geographically isolated wetlands, those entirely surrounded by uplands, provide numerous landscape‐scale ecological functions, many of which are dependent on the degree to which they are hydrologically connected to nearby waters. There is a growing need for field‐validated, landscape‐scale approaches for classifying wetlands on the basis of their expected degree of hydrologic connectivity with stream networks. This study quantified seasonal variability in surface hydrologic connectivity (SHC) patterns between forested Delmarva bay wetland complexes and perennial/intermittent streams at 23 sites over a full‐water year (2014–2015). Field data were used to develop metrics to predict SHC using hypothesized landscape drivers of connectivity duration and timing. Connection duration was most strongly related to the number and area of wetlands within wetland complexes as well as the channel width of the temporary stream connecting the wetland complex to a perennial/intermittent stream. Timing of SHC onset was related to the topographic wetness index and drainage density within the catchment. Stepwise regression modelling found that landscape metrics could be used to predict SHC duration as a function of wetland complex catchment area, wetland area, wetland number, and soil available water storage (adj‐R 2 = 0.74, p < .0001). Results may be applicable to assessments of forested depressional wetlands elsewhere in the U.S. Mid‐Atlantic and Southeastern Coastal Plain, where climate, landscapes, and hydrological inputs and losses are expected to be similar to the study area.

Highlights

Connectivity has long been recognized as an important concept in landscape ecological research and planning (Merriam, 1984; Taylor, Fahrig, Henein, & Merriam, 1993; Turner, 1989)
The removal of field‐derived predictor metrics from stepwise regression led to a final geographic information system (GIS)‐based model of cumulative surface hydrologic connectivity (SHC) duration with more support, as indicated by a decrease in Akaike Information Criterion corrected (AICc) value of 4.2 (Burnham & Anderson, 2002). These results suggest that among the variables used in this study, GIS + Field and GIS‐based models performed comparably in their ability to explain variability in SHC patterns among forested Delmarva bay wetland catchments
There are still gaps in our scientific understanding of the diverse roles that geographically isolated wetlands and temporary channels play in the hydrology and ecology of nearby waters (Costigan, Jaeger, Goss, Fritz, & Goebel, 2016; Datry, Pella, Leigh, Bonada, & Hugueny, 2016; McLaughlin & Cohen, 2014; Vanderhoof et al, 2017)

Summary

Introduction

Connectivity has long been recognized as an important concept in landscape ecological research and planning (Merriam, 1984; Taylor, Fahrig, Henein, & Merriam, 1993; Turner, 1989). Attributed in large part to their dynamic nature, wetlands perform a number of important hydrologic, biogeochemical, and habitat/food web functions with local and regional effects (McLaughlin & Cohen, 2014; Sharitz, 2003). Wetlands supply materials such as water and organic matter (source function), remove harmful materials such as excess nutrients and pathogens (sink function), and provide habitat or refugia for organisms such as fish and aquatic insects (Leibowitz, Wigington, Rains, & Downing, 2008; Rains et al, 2016). The type, magnitude, and scale of these functions depend considerably on the degree and mechanism of hydrologic connectivity between wetlands and other landscape elements (Cohen et al, 2016; Leibowitz, Mushet, & Newton, 2016; Marton et al, 2015)

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Conclusion