Masters Thesis


CREATED FOREST WETLANDS - A FRAMEWORK FOR BETTER SUCCESS

Jens Geratz


A study was initiated to evaluate success criteria for various wetland creation projects in eastern North Carolina, USA.  Both qualitative and quantitative criteria for soils, hydrology and vegetation were compared with reference forests to determine if they were adequate for the development of specific forest community types.  Most created wetland projects failed to identify forest community types and the basic environmental factors that drive these systems .  This led to improper wetland tree species selection and apportionment in the planting mix.  Poor design and implementation confounded possible success for these created wetlands.

A wetland creation project in Beaufort County, North Carolina was intensively studied to evaluate the major forces driving wetland creation projects, including hydrology, topsoil depth and initial tree stocking levels.  A surface water model was used to approximate the hydrology of nearby Durham Creek.  Detailed topographic maps were useful in determining zones of various flooding percentages and topsoil depth.  Planted trees and volunteer vegetation were described in relation to elevation and topsoil depth.  A tree growth model was developed to illustrate the effects of various hydrologic and topsoil depth regimes on early successional forested wetland development.  By coupling the model with plot samples and the various zones in the intensive study site, it was possible to evaluate the future community structure against that of reference forests stands.

In the context of wetland mitigation, results suggest that the success of wetland creation projects  were highly dependent on goals established prior to implementation.  That is, knowledge of the factors governing specific community types, including hydrologic regime and tree species selection is crucial in forested wetland development and consequently regaining lost wetland functions and values associated with these community types.  The tree growth model predictions of future overstory composition reveal mixed success, where poor growth can be attributed to areas with poor topsoil replacement and/or flooding frequency that exceed the species limits.