Distribution Patterns in Melampsorella in the National Forests and Parks of the Western States

Publisher Website
Google Scholar
Abstract
SUMMARY Further evidence for the existence of two species of Melampsorella was obtained from a study of their distribution. Many areas in the Western States were visited during the summer of 1941, and in the forests where both hosts and the disease were found detailed studies were made on the distribution of the two forms. Seventy-five collections and over 150 detailed observations were made. In practically every area visited one or the other species was found to be dominant, even though both hosts were abundant, indicating that these two species differ in their physiology as well as in their morphology. Two distinct distribution patterns were thus obtained. The disease was collected in the following National Forests: Uintah N.F., Wasatch N.F., Powell N.F., Utah; Kaibab N.F., Ariz.; Mt. Hood N.F., Ore.; Teton N.F., Wyoming N.F., Medicine Bow N.F., Wyo.; Harney N.F., Black Hills N.F., S. D.; and in the following National Parks: Grand Canyon N.P., Ariz.; Sequoia N.P., Yosemite N.P., Calif.; Crater Lake N.P., Ore.; Mt. Rainier N.P., Wash.; Glacier N.P., Mont.; Yellowstone N.P. and Grand Teton N.P., Wyo. In the forests of the Rocky Mountain States where Picea and Abies are abundant the disease was found to be more severe than heretofore believed. Many trees were found to be partially or completely dead; many were dwarfed or stunted. In some areas in Wyoming the disease occurred in such abundance that it was considered to be of epidemic proportions. Trunk infections were found to be particularly harmful. In the Grand Canyon National Park many older trees were found which had been broken off evidently due to weakening of the main trunk at that point. Trunk infections of young trees soon cause their death. Differences in growth habits which produce a dense, compact broom on Abies and an irregular diffuse broom on Picea were found to be a constant and fairly reliable character, and are believed to be due to apical dominance which is present in the species on Picea and absent in the species on Abies.

This publication has 4 references indexed in Scilit: