EFFECTS OF SIMULATED MOOSE BROWSING ON DRUMMOND'S WILLOW

A study was conducted from 1973 to 1983 on the north slope of the Uinta Mountains in Utah and Wyoming to evaluate the effects of varying simulated levels of winter browsing by moose (Alces alces) on Drummond’s willow (Salix drummondiana). Plants within a 0.4-ha exclosure were clipped annually with levels of removal of 0%, 30%, 60%, or 90% of the cumulative growth < 0.5 cm in diameter. Numbers of stems, branches, and suckers per plant were decreased by all clipping intensities, but only the 90% treatment produced declines exceeding those observed among control plants. After 8 years of sustained clipping, browse production in the 30% treatment had declined to an average of 35% of the production in 1973. Comparable levels of browse production in the other two clipping intensities were 27 and 10%, respectively, of original levels. Plants clipped at the 90% rate showed significantly (P < 0.05) higher mean protein and phosphorous values than plants in other treatment levels. A comparison of 1- to 5-year old willow growth revealed that crude protein and phosphorous content and digestibility decreased with increasing age