MOOSE DAMAGE TO PRE-COMMERCIALLY THINNED BALSAM FIR STANDS IN NEWFOUNDLAND

Abstract

In Newfoundland, dense balsam fir (Abies balsamera) stands dominate many sites after logging. At 10-12 years of age, these stands are mechanically thinned to reduce stem density from about 30,000 stems/ha to 2000 stems/ha. Thinning enhances tree growth through reduction of competition for light and nutrients. An island-wide survey of 21 stands showed that moose had browsed 3-45 percent of firs taller than 1.8 m, and severely damaged (more than 50 percent current growth and leader removed) up to 22 percent of stems >3 m in thinned stands, while unthinned stands received little damage. Moose pellet density was highest in thinned stands and regression analysis suggested that moose pellet density was an important predictor of browsing damage. Regressions of browsing levels in all stands excluding pellets and using vegetation variables indicated that damage decreased with increased young balsam fir density, suggesting that thinning stands resulted in a superior feeding condition for moose. Analysis of data from thinned stands alone showed that browsing intensity was related to the percent of all trees under 3 m that were balsam fir. Thinned stands may produce more food of better quality than do trees growing in the more competitive unthinned condition. Recommendations for management to reduce damage including timing of operations, edge of stand features, and stem density are discussed.