The Twig-Count Method for Measuring Hardwood Deer Browse

Results of three methods of determining the weight of woody deer (Odocoileus virginianus) browse were compared in a recent study in the Pocono Mountains of Pennsylvania. The three methods were twig-count, weight-estimation, and clip-and-weigh. The twig-count method described in this study converts a count of twigs to weight of browse by use of an average weight per twig for individual species. The study was conducted in 2-year-old dormant hardwood sprout growth produced for deer by cutting and bending sapling- and pole-sized trees. Four observers used the twig-count and weight-estimation methods and one of the four observers also used the clip-and-weigh method on the same thirty, 100-square-foot, circular plots. There were no significant differences in accuracy among the three methods for determining the weight of browse material. However, the average time required per plot for each method was as follows: (1) weight-estimation--3.2 minutes, (2) twig-count--4.6 minutes, (3) clip-and-weigh--21.8 minutes. The results show that the twig-count method is nearly as fast as the weight-estimation method and just as accurate as the clip-and-weigh method. And the twig-count method gives results that can be analyzed statistically and can be used for measuring both browse production and browse utilization on permanent sample plots. In the study, the twig-count method was tried on sprouts of only five hardwood species (Acer rubrum, Prunus serotina, Betula populifolia, Populus tremuloides, and Quercus rubra); additional research is needed before the method can be applied to other kinds of hardwood deer browse.