Effects of plant-community change on wetland denitrification
Eutrophication and invasive species are two of the strongest drivers of negative
ecosystem change in wetlands. In much of the Midwest, wetland degradation associated with eutrophication has promoted replacement of a native plant, Carex stricta Lam. (tussock sedge), a keystone species in sedge-meadow wetlands, with the invasive grass Phalaris arundinacea L. (reed canarygrass). Both species are ecosystem engineers that strongly influence habitat structure, but they do so in different ways. Carex stricta tussocks impart microtopographic heterogeneity, facilitating plant diversity and enhancing ecosystem functioning. In contrast, P. arundinacea produces copious, persistent biomass that suppresses diversity and reduces heterogeneity.
Given the scale of substitution of a beneficial, native ecosystem engineer with an invasive
ecosystem engineer (by the early 2000s, P. arundinacea dominated 26% of Wisconsins emergent wetland acreage), it is critical that we understand how this change influences ecosystem services performed by wetlands. Denitrification (microbial conversion of biologically available nitrate to gaseous forms), which can help offset nutrient pollution in wetland and aquatic systems, is one such service.
The focus of this research is to investigate how conversion of C. stricta meadows to P. arundinacea dominance influences denitrification, and the extent to which wetland restoration returns lost denitrification services.