Date of Award
Doctor of Philosophy
Events at Goose Lake, a Class IV wetland in central Iowa, were observed from 1974 to 1979 in an attempt to determine (a) how production and species composition are affected by a natural drawdown and subsequent refilling of a marsh, (b) the effects of historical events on present marsh character, (c) how the historical vegetation compares with that present today, and (d) the importance of annual events on the character of a marsh;Vegetation was sampled using quadrats placed along transects placed at regular intervals around the marsh. The percent cover of each species present in each quadrat at stages throughout the drying and refilling stages was recorded. These data were analyzed to determine how cyclical events influenced production, species composition, and cover. The long-term changes in vegetation were examined by comparing the species listed in an earlier study with the species observed during the present study. Phenological events were recorded to establish a chronology of annual events and to determine what environmental triggers are essential to marsh dynamics;At the beginning of the study, the marsh was open (lake marsh stage) due to high water and muskrat damage. In 1975, the water level began dropping and became nearly dry in 1976. In 1977, the marsh achieved the dry marsh stage and exposed large areas of mud flats where marsh ephemerals like Bidens cernua and Cyperus erythrorhizos germinated in large numbers. Above ground standing crop samples, taken in 1974, 1976 and 1978, showed an increase in biomass each year. Species richness, measured in 1974, 1976 and 1978, increased the first three sampling years, but decreased the final sampling year. Sorenson's index showed the marsh to be most dissimilar in 1974 compared to 1976; it showed the 1979 conditions becoming more similar to those that prevailed at the beginning of the study.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Dean Melvin Roosa
Roosa, Dean Melvin, "Marsh vegetation dynamics at Goose Lake, Hamilton County, Iowa: the role of historical, cyclical, and annual events " (1981). Retrospective Theses and Dissertations. 6943.