Date of Award
Doctor of Philosophy
A vegetation inventory was conducted along 200 miles of the North Platte and Platte rivers in Nebraska. Twelve major vegetation types were identified using Twinspan, a computerized reciprocal averaging ordination technique. Herbaceous communities included annual and perennial mudflats, marshes, lowland grasslands, and upland grasslands. Lowland shrub communities were dominated by Salix exigua and Amorpha fruticosa, and upland shrub communities were characterised by Amorpha and Cornus drummondii. Populus-Salix and Populus-Elaeagnus forests dominated on wetland sites, while Populus-meadow Populus-Juniperus, and mixed hardwood forests dominated on moderately dry sites;Trees on the Platte River floodplain primarily established following the 70% decline in mean annual discharge since 1930. Forests west of Overton generally established between 1930 and 1950, while forests east of Overton have generally developed since 1950. The effects of hydrology on the radial growth of Populus deltoides, Salix rigida, and Juniperus virginiana were assessed by comparing growth (mm) of these species during periods of low mean discharge (1930-39 and 1967-70) with growth (mm) during periods of high mean discharge (1920-29 and 1971-74). Populus incremental growth did not differ significantly during periods of high and low discharge. Salix, however, grew significantly more, and Juniperus grew significantly less during periods of high mean discharge;The short seed-release (May-July) and seed viability (2-3 weeks) periods of Populus and Salix, the pioneer arboreal species, limit seedling establishment of these species to the period from mid-May through August. Mudflats with fine textured soils (19% silt, 15% fine sand, 63% sand), high soil moisture (18% to 28%), and a long period of substrate exposure (74 days) are necessary before widespread seedling establishment occurs;Populus and Salix were found on soils ranging from coarse sand to silty loam. Elaeagnus angustifolia was generally confined to poorly drained silty clay soils, and Juniperus was found primarily on well-drained sandy to silty loam soils. An idealized vegetation development scheme was proposed based on the site preferences, germination and establishment requirements, age structure, and the vegetation inventory of the major arboreal plant communities.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Paul Jon Currier
Currier, Paul Jon, "The floodplain vegetation of the Platte River: phytosociology, forest development, and seedling establishment " (1982). Retrospective Theses and Dissertations. 8339.