Effect of Simulated and Natural Deer Browsing on Mountain Maple

Abstract

This long-term study (1952-62) was made to measure the growth response of mountain maple (Acer spicatum) in Minnesota to different intensities of simulated and natural browsing by white-tailed deer (Odocoileus virginianus). For the test clumps browsed by deer, the annual growth of twigs within reach of deer (ground level to 7 feet) was measured in late October and remeasured in late April to determine the amount removed. Similar information was obtained on test clumps within two exclosures. To simulate various intensities of browsing, the annual growth was clipped 20, 40, 60, 80, and 100 percent. The degree of browsing had no apparent direct effect on the amount of growth the following season; other environmental factors were more important. Tolerance of mountain maple to browsing was high, however, since only 1 of 6 clumps had died after 100 percent of the annual growth had been clipped for 9 years. Sustained production of food within reach of deer was maintained at a level of use of about 80 percent. Since clumps are established primarily by the growth of underground stems, opportunities for management by cutting or by the application of common weed killers are excellent. Long-term herd management is impossible unless the deer population can be held at a level that permits adequate growth and reproduction of browse species in winter yarding areas. Adjusting deer numbers to the amount of food produced has been difficult because little is known about the degree of browsing important forage plants can withstand and still remain in a healthy productive condition. The objective of this study was to determine the level of use of mountain maple that will stimulate maximum browse production on a sustained yield basis. Test clumps of mountain maple were subjected to simulated and natural browsing by white-tailed deer. Mountain maple is a preferred and staple browse species over much of its range in the lake states, northeastern United States, and southern Canada west to the prairie provinces (Krefting et al. 1956:434). In Minnesota, mountain maple is one of the more palatable and nutritious deer foods. Tests by Fashingbauer and Moyle (1963) have shown that mountain maple has no serious nutrient deficiencies for deer. Mountain maple grows in clumps and frequently reaches a height of 20 feet or more and a diameter of 3 inches. Studies of the structure of clumps and their regeneration characteristics show that clumps are separate (R. K. Seemel, 1963, unpublished report, School of Forestry, University of Minnesota). New clumps are established from underground stems. Sprouts are produced from the growth of axillary buds in these stems. Some regeneration results from layering; stems of seedling origin are rare. Mountain maple has medium moisture and nutrient requirements and low heat and light requirements (Bakuzis 1959, Bakuzis and Hansen 1962). The study was made within the 6,000acre Jonvik deer yard on the Superior National Forest in Cook County, Minnesota. Forest cover is chiefly pole-size balsam fir (Abies balsamea), white spruce (Picea glauca), and white cedar (Thuja occidentalis), with scattered paper birch (Betula papyrifera), black spruce (Picea mariana),