Degree Type

Dissertation

Date of Award

1989

Degree Name

Doctor of Philosophy

Department

Botany

First Advisor

Arnold van der Valk

Abstract

Seasonal changes in vegetation in monsoonal wetlands in the Keoladeo National Park, Bharatpur, India, are related to changes in mean water depths which are lowest just before the onset of the monsoon (June 1984; <1 cm), highest immediately after the monsoon (October 1985; 89 cm). Water levels decline slowly over the winter (March 1985; 14 cm);Grazing by Greylag (Anser anser rubrirostris) and Barheaded (Anser indicus) creates openings in the emergent vegetation. The mean distance to open areas, i.e., areas free of vegetation, along grazed transects, before goose grazing was 193 m and after grazing, 43 m. For ungrazed transects, no change in mean distance to open water patches was observed during the same interval (344 m and 339 m, respectively). Seeds dispersed by the feeding and defecation of geese can potentially influence re-establishment of plants in openings;Areas grazed by geese have a seed bank that contains 19-50 species per m[superscript]2 and a total of 3,425-16,195 seedlings per m[superscript]2 as determined by the results of the moist soil and flooded treatments combined. During summer drawdown, annuals and seedlings of woody plants become established in open areas grazed by geese, but no seedlings of any species are found in ungrazed areas. The seed bank contains many species that were not found as adult plants in either grazed or ungrazed sites. Field observations, however, indicate that clonal growth of surviving individuals is primarily responsible for the re-establishment of vegetation in areas opened up by goose grazing, and that recruitment from the seed bank is only of secondary importance;In an experimental clipping study conducted in Bharatpur, India, four plant species were either clipped weekly, every two weeks, or left unclipped while growing at one of 3 water levels (0 cm, 3 cm, or 13 cm below the surface of the water). When clipped underwater, individuals of Ipomoea aquatica Forsk., Paspalidium punctatum A. Camus, and Paspalum distichum Linn., usually died but not those of Nymphoides cristatum Kuntze. In a companion field study in a monsoonal wetland in the nearby Keoladeo National Park, plants of Ipomoea aquatica and Paspalum distichum also usually died when clipped underwater.

DOI

https://doi.org/10.31274/rtd-180813-11135

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Beth Ann Middleton

Language

en

Proquest ID

AAI8920168

File Format

application/pdf

File Size

148 pages

Included in

Botany Commons

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