Chrissy Pruett
Can vegetation biomass and species diversity serve as indicators of nutrient enrichment in Midwest freshwater wetlands?
BSES Senior Research 2003

Surface water inorganic nitrogen (N) and phosphorous (P) and emergent vegetation biomass and species diversity were measured in ten freshwater wetlands of Northeastern Indiana to evaluate relationships between plant community structure and function and wetland nutrient condition.

Live plus dead aboveground biomass was positively related to surface water NH4-N (R2 = 0.38) and PO4-P (R2 = 0.30). Stem height, another index of plant growth, also increased with surface water NH4-N (R2 = 0.71, p < 0.0001) and PO4-P (R2 = 0.59, p < 0.0001). In contrast to indices of plant growth, which increased with nutrients, attributes related to species composition declined with increasing nutrient concentrations. Species richness was inversely related to surface water NH4-N (R2 = 0.35, p <0.07). The decline in species richness was attributed to an increase in abundance and biomass of aggressive species (Phalaris, Tyhpa) that increased with NH4-N (R2 = 0.66, p < 0.01).

Attributes related to plant productivity (aboveground biomass, stem height) and species composition (Phalaris and Typha biomass) are useful indicators of nutrient condition of freshwater wetlands of Northeast Indiana. These attributes need to be tested in other ecoregions and geographic areas to gauge their effectiveness across a wide range of environmental conditions and wetland types.