Tree Invasion of Montane Meadows in Oregon

Abstract

Mesic montane meadows [Rubus parviflorus/Pteridium aquilinum and Bromus carinatus/Rudbeckia occidentalis associations] in the Cascade Mountains of central and southern Oregon were invaded recently by trees [Libocedrus decurrens, Abies concolor, A. magnifica, A. grandis, A. procera, A. amabilis, Pinus monticola, P. contorta, Tsuga mertensiana, T. heterophylla and Pseudotsuga menziesii] from the adjacent forests. Cessation of sheep grazing coincides with the initiation of the tree invasions, but the absence of frequent fires and cool moist weather may have contributed to the conditions which favored the unstable ecotones.