Effects of wetland plant functional group (GD) on carbon storage and nitrogen removal
by Dr. Changwoo Ahn
The uncertain reality of created and restored wetland development suggests that there may be ways to improve the design and management of these wetlands to ensure a greater likelihood of structural and functional success. One top research priority is understanding how the gain of plant diversity at early stages of restoration affects the development of soil properties and processes. Our study addresses this research need by quantifying the effects of functional group diversity of wetland herbaceous vegetation in outdoor mesocosms on the development of carbon storage and nitrogen loss through denitrification. We hypothesized that (1) increased functional group diversity would promote greater plant productivity through more efficient resource capture; (2) enhanced plant productivity would increase labile stocks of soil organic carbon and nitrogen; and (3) these stocks would promote the development of denitrification. We studied four functionally distinct species: Eleocharis obtusa (i.e., obligate annual), Mimulus rigens (facultative annual), Juncus effusus (i.e., interstitial reed), and Carex vulpinoidea (i.e., interstitial tussock). To quantify diversity effects on plant structure, we measured plant morphological traits and above- and below-ground biomass; to quantify diversity effects on soil carbon and nitrogen properties, we measured soil organic and total carbon and nitrogen, and denitrification enzyme activity. Statistically significant differences (p<.05) on certain above-ground morphological traits (i.e., basal diameter, stem count, and stem height) between functional groups were found for the first growing season. The experiment is on-going and complete results garnered at the end of the second growing season is under analysis. This research was sponsored by the Thomas F. and Kate Miller Jeffress Memorial Trust Fund and a Virginia Academy of Sciences small project research grant to the Ahn Wetlands Research Lab, George Mason University. Thanks to both the 2012 and 2013 EVPP 378 – Environmental Sustainability classes for the construction of the facility, preparation of the experimental mesocosms, and data collection.
PhD student Alicia Korol sorting out the belowground biomass of wetland plants harvested.