Forest restoration increases isolated wetland hydroperiod: a long‐term case study

Geographically isolated wetlands (GIWs) are well known as “hotspots” for biodiversity and other ecosystem services, making their value on landscapes disproportionate to the area they occupy. GIWs are dependent on regular cycles of inundation and drying, which makes hydrology a primary controlling variable for sustaining functions and associated ecosystem services. Although human activity has degraded GIWs in many regions, relatively little work has focused on upland management as a way of sustaining, or even improving, GIW structure and function. We present a case study of longleaf pine forest restoration, by hardwood removal, on the characteristics of a wetland hydroperiod over a 10‐year study. Our study wetland, W‐51, is 0.89 ha with a catchment area of 31.2 ha located on a ~11,400‐ha private preserve in Baker County, Georgia (31.250° N, 84.495° W). Beginning in 2006, continuous water level and climate data were recorded in the wetland and adjacent well transects across the wetland catchment. In autumn 2009, hardwoods were removed or deadened in the catchment resulting in a 37% reduction in tree cover. The effects on the hydrologic system were measured through 2016 by examining pre‐ and post‐removal water levels, water yield ecosystem (WYe), and standardized recession rates (RRₛₜd). The study included periods of above and below normal rainfall. Generally, wetland hydroperiods began in December and ended in May, but varied with rainfall pattern and amount. Hardwood removal increased WYe and decreased RRₛₜd resulting in greater catchment water availability as reflected in water levels. Hardwood removal affected both the ascending and recessing limbs of wetland hydroperiods, substantially increasing the availability of ponded water in the wetland. Our results quantify changes in wetland hydrologic characteristics associated with forest management activities, which appear to have reduced forest water demand. Our study was a management case study, limited in scope but conducted in a realistic setting. More extensive studies (paired, replicated designs) are needed to better understand the implications at both the local scale, that is, managing critical aquatic habitat for wildlife populations, and at the regional scale, that is, providing support for landscape‐scale connectivity and water yields.