THE EFFECTS OF GRAZING ON ALPINE VEGETATION - A COMPARISON OF THE CENTRAL CAUCASUS, REPUBLIC-OF-GEORGIA, WITH THE COLORADO ROCKY-MOUNTAINS, USA

This study is a comparison of certain facets of the alpine vegetation in Rocky Mountain National Park, U.S.A. with that of Mt. Kazbegi, central Caucasus, Republic of Georgia. There are many similarities in climate and geological history between the two sites. Also, their alpine floras contain 60 congeneric and 17 conspecific species, but great disparity of human history exists between the two sites. For at least 2000 yr, the Georgian area has been occupied by herders and their flocks of domestic sheep and, to a lesser extent, domestic cattle. The New World study area has experienced little influence of domestic stock. Comparative work with plants between sites included vegetation composition, phenology, seed germinability, growth rates, responses to clipping, digestibility, and arrangement of vegetative and reproductive parts within related taxa. Workers have suggested that genetic change can occur in relatively short periods of time in response to herbivory. This hypothesis was investigated by comparative studies of response to clipping, digestibility of selected species, dominant plant families at the two sites, and the morphology of plant structures. The clipping and digestibility studies did not fit the common wisdom concerning response to directional selection by herbivores. Plant family patterns and morphology may reflect the long presence of domestic stock in the Caucasus. The relationship between ungulates and higher plant evolution merits further clarification.