Date of Award:

5-1-1980

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

Richard J. Shaw

Committee

Richard J. Shaw

Committee

Ivan G. Palmblad

Committee

Michael A. Walsh

Committee

Robert Q. Oaks Jr.

Committee

Clyde J. Hurst

Abstract

The vegetation on the neoglacial deposits below six glaciers in Grand Teton National Park was examined. The deposits at the six sites range from large terminal moraines to steep debris slopes to relatively flat debris accumulations. The sites are characterized by a diversity in topography, climate, and aspect. The environmental millieu the plants are occupying is dominated by disturbance, including mass-wasting, climatic fluctuations, and possible herbivory. One hundred and four species of vascular plants were collected from the six sites. Most of these are typical arctic-alpine species. Transplants of late successional species failed to survive because of dessication, snow kill, physical disturbance, and possible herbivory, or a combination of these. Diaspore trapping suggests that few diaspores are dispersing onto the deposits at Teton and Schoolroom Glaciers, even though trapping was done at a time when most reproductive structures are maturing and ready to disperse. Most of the diaspores trapped consisted of light wind dispersed seeds and fruits from families common in vegetation on and around the sites. Clustering of the sites using physical characteristics and presence or absence of species showed that physical similarity was not always correlated with floristic similarity. Some physical characteristics are more important than others in determining species distributions. The size of the floras at each site seems to be controlled by a combination of snow melt, aspect, rock type, exposure to storms and winds, and especially characteristics of the surrounding vegetation. Average plant cover at the Teton and Schoolroom sites is quite low, from 5% to 12%. This is probably due to a combination of continual physical disturbance and a severe and fluctuating climate. Quadrat studies at Teton and Schoolroom Glaciers show that many of the species at these two sites are restricted to certain portions of the deposits. Some common habitat types on these deposits include crevice sites, mudflats, moraine slopes, and flat sandy areas. Several species reach their maximum abundance on the steep, unstable moraine slopes, and are good indicators of physical disturbance. Species importance curves for the moraines at Teton and Schoolroom Glacier approach geometric series, indicating well developed dominance by one or a few species in a severe environment. Two types of succession seem to be occurring at the sites, both of which should eventually converge on the same mature vegetation type. Cyclical autosuccession is found on unstable substrates like the moraine slopes at the sites, with disturbance determining the species composition and dynamics. Directional succession is found on relatively more stable substrates, with the species composition and speed of succession controlled by chance dispersal events and possible herbivory. Climatic fluctuations are important in both types of succession. Eventually, the vegetation on the deposits at these six sites should be similar in most ways to the vegetation which dominates surrounding areas outside the influence of the glaciers.

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