| This study of wetland plant community ecology consisted of three related but distinct projects carried out at the Cedar Creek Natural History Area (CCNHA) in east-central Minnesota. The first project involved establishing permanent plots along transects in fifteen wetlands at the CCNHA covering a range of wetland types. The plots are used to: (1) characterize the non-wooded wetlands at the CCNHA; (2) determine correlations of plant community type with environmental factors; (3) examine changes over a 5-year period; and (4) provide a data set for long-term monitoring and future comparisons. Vegetation patterns were analyzed using the multivariate statistical techniques of classification (using TWINSPAN) and ordination (using DECORANA). Plant community types were then correlated with environmental variables, including water levels, water chemistry and soil characteristics.; The second project was a fertilization experiment along a gradient going from the upland dominated by Andropogon gerardi to a Carex lacustris dominated wetland. The gradient divides naturally into four zones with different species composition, called "Dry," "Moderately Dry," "Moderately Wet," and "Wet". Treatments were: ALL (N, P, K, Ca, Mg, S and trace metals); MINUS P (all nutrients except P); MINUS N (all nutrients except N); and CONTROL (no additions). Species presence and percent cover were recorded at monthly intervals during the growing season from 1987 through 1990. Nitrogen limits productivity in the "Dry Zone" and has some importance in the "Moderately Dry Zone", but is not limiting in the wetter zones. There was no significant response to any other nutrient. Zones also differed in their response to drought.; The third project investigated the response of several wetland species to changes in water availability by transplanting block of soil and vegetation reciprocally between zones of vegetation correlating with a soil-moisture gradient. Species included Onoclea sensibilis, Carex haydenii, Scirpus cyperinus, Thelypteris palustris, and Carex lacustris. Species presence, density, and percent cover were recorded monthly during the growing season from 1987 to 1991. Species varied in their responsiveness to both transplantation and drought. Water levels were of major importance but were not always the immediate determinant of species distributions. Other physical factors or biotic interactions must play a role. |
