Identifying ecohydrological patterns in natural forested wetlands useful to restoration design

Abstract

Wetland restoration projects across the United States commonly lack the species and hydrology of the targeted community being restored. A better understanding of natural wetlands would help restoration project designers achieve community composition and hydrologic regimes that more closely resemble natural conditions. We investigated two different methods to identify patterns in hydrologic regime useful to restoration design. The first method was based on success criteria commonly used by North Carolina wetland mitigation projects. The second method was based on The Nature Conservancy's Indicators of Hydrologic Alteration. To test these two methods, we collected hydrologic and compositional data across the natural variation of nonriverine wet hardwood forest stands, a rare wetland community type commonly restored in North Carolina. Our results show that hydrologic parameters from the first method, based on current success criteria used in North Carolina, are not related to community composition. Hydrologic parameters from the second method, e.g. the maximum water table level over a 3-day span, explained much of the variation in nonriverine wet hardwood forest community composition. Our results found that clear relationships do exist between hydrologic regime and community composition. Hydrologic parameters that are related to community composition need to be used as success criteria in future restoration designs. This will ensure that projects establish the appropriate hydrologic regime necessary to foster the desired wetland community type. 379Normal precipitation is the 30-year average from 1971 to 2000. Stands are ranked in descending order from wettest to driest for the study period compared with normal conditions. For each stand N denotes nonriverine wet hardwood forest, M denotes mesic mixed hardwood forest, and S denotes nonriverine swamp forest.

Novel ways to assess forested wetland restoration in North Carolina using ecohydrological patterns from reference sites

“…Detailed well placement methods are described in Johnson et al . (). Water table levels were recorded four times per day using a pressure water level data logger (Infinities USA, Port Orange, FL, USA).…”

“…Detailed study site selection criteria and methods are available in Johnson et al . (). Nonriverine wet hardwood forests occur on broad, flat interstream divides in the lower coastal plain of North Carolina and southeastern Virginia (Schafale, ).…”

“…Our preliminary research at the reference sites found that certain measures of water table levels are strongly correlated with canopy species composition across these three different communities (Johnson et al ., ). Restoring the appropriate hydrology for a particular community type will help to ensure that conditions are right for the targeted community's unique set of species.…”

“…We focus on nonriverine wet hardwood forests to test ecologically relevant ways to quantify water table levels, a common proxy for wetland hydrology. We chose this community because it is the most commonly restored forested wetland in North Carolina, and it occurs along a hydrologic gradient, based on slight but important differences in water table level, with two other communities: mesic mixed hardwood forests and nonriverine swamp forests (Schafale, 1999 andJohnson et al, 2012). The former community is not as wet as nonriverine wet hardwood forests, whereas the latter community is wetter.…”

Linking Plant Ecology and Long-Term Hydrology to Improve Wetland Restoration Success

“…The few studies that have attempted to quantify the hydrology of wetland plant communities did so over a short period of time (e.g., less than three years), taking little account of year-to-year variability in weather patterns that strongly affect long-term hydrology and vegetative growth in a wetland ecosystem. For example, Johnson et al (2011) collected water table depths at several wetland sites in eastern North Carolina over a seven-month period to examine [a] Source: Schafale and Weakley (1990). [b] Source: Otte (1982) and Hall and Penfound (1939).…”