Historical trends in willow cover along streams in a Southwestern Montana cattle allotment
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Concern over the apparent scarcity of tall willows [Salix sp.] prompted changes in livestock grazing management in a southwestern Montana mountain valley to avoid degradation of riparian and aquatic habitats. We assessed potential improvement in the abundance of tall willows following implementation of a new management strategy by determining the effect of historic grazing patterns on willow canopy along streams within the USDA Forest Service Long Creek cattle grazing allotment. The study area was dominated by Salix geyerana, S. boothii, Carex spp., and Poa pratensis. Willow canopy cover by stream reach was measured from aerial photos taken in 1942, 1965, and 1987. Cover from each year was compared for change over the 46-year record. Willow canopy cover fluctuated along the streams in the allotment, but the general trend was upward from 1942 to 1987. Willow stem population demography was evaluated to ascertain whether historic grazing patterns had affected stem replacement. Stem age classes were normally distributed with a replacement cycle similar to those reported in other areas of the western USA and Canada. These data sets suggest that extended periods of rest (>3 years) are not necessary for willow recovery if livestock or wildlife use is closely controlled.