WILD UNGULATE INFLUENCES ON THE RECOVERY OF WILLOWS, BLACK COTTONWOODAND THIN-LEAF ALDER FOLLOWING CESSATION OF CATTLE GRAZING IN NORTHEASTERN OREGON

Restoration of degraded riparian ecosystems is of great importance for the recovery of declining and endangered stocks of Columbia River sal monids as well as riparian-obligate wildlife species. Willows (Salix s pp.), thin-leaf alder (Albus incana), and black cottonwood (Populus tr ichocarpa) are important features of western riparian ecosystems havin g multiple functional roles that influence biological diversity, water quality/quantity, and aquatic/terrestrial food webs and habitats. Rem oval of domestic livestock and the construction of big game exclosures have been hypothesized to be effective restoration techniques for rip arian ecosystem as well as for salmonid habitat recovery. Following mo re than a century of livestock grazing, cattle were removed from Meado w Creek in 1991 and the rates of riparian shrub recovery were measured for the two years following. Elk and deer proof exclosures were const ructed to quantify the browsing influences of native large ungulates. The initial mean height of 515 deciduous trees and shrubs (14 species) was 47 cm. After two years in the absence of livestock, significant i ncreases in height, crown area, crown volume, stem diameter and biomas s were measured both outside and inside of the exclosures. Mean crown volume of willows increased 550% inside of wild ungulate exclosures an d 195% outside. Black cottonwood increased 773% inside and 808% outsid e, while thin-leaf alder increased 1046% inside and 198% outside. init ial shrub densities on gravel bars were low averaging 10.7 woody plant s/100m(2). Shrub numbers significantly increased approximate to 50% (t o 15.8 plants/100m(2) m or one new shrub for every 9 meters of transec t length) outside of elk and deer proof exclosures through both clonal and seedling establishment. At the beginning of the study (1991), cat kin production on willows was low (i.e., only 10% produced catkins). W ild herbivores had a significant influence on the reproductive output of willows; in 1993 catkins were produced by 34% of the tagged willows within exclosures but only 2% outside of exclosures. Wild herbivores were found to have significant influences on the rate of height growth of black cottonwood. For willows, wild herbivores had a significant i nfluence on the rate of growth for the parameters of height, crown are a, crown volume, and standing biomass. Nevertheless, due to the inhere nt resilience and adaptions to natural disturbance processes displayed by the riparian species, there was a rapid and positive response to c essation of those land use activities (i.e. cattle grazing) that cause d habitat degradation and/or were preventing recovery.