The effects of eutrophication on wetland plant communities.

Abstract

The first two parts of this study are concerned with a natural field project in which I measured specific plant traits, community state variables, species frequencies, and soil fertility in a large scale comparative study of eight Great Lakes wetlands. I asked the following questions: (1) Are there measurable, quantifiable differences between wetlands--with respect to plant traits, community state variables and fertility, and (2) Are there empirical relationships between plant traits/community state variables and fertility variables. Significant differences between four productive and four unproductive wetlands were found across all the plant traits, except rhizome diameter, all the community state variables and all the fertility variables, except nitrogen. Productive wetlands had lower species richness and were taxonomically distinct from unproductive wetlands. I found that total phosphorus was the most important independent variable and that the most important dependent variables were plant height, standing crop, and species richness. I ran a large outdoor screening experiment bioassaying 40 wetland plants, at two fertility levels, to measure a trait I call 'biomass sensitivity'. I found that all species produced more biomass in the fertile treatment. By comparing species according to the proportional 'biomass sensitivity' (P($\Delta$B)) trait, that is the proportional change in biomass between high and low nutrients, I find there are no differences between species. (Abstract shortened by UMI.)