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While balsam fir (Abiesbalsamea (L.) Mill.) dominated forests are vanishing from the southwest end of Isle Royale National Park, Michigan, renewal of fir stands is occurring on the northeast end. We speculate that the difference is related both to severe browsing by moose (Alcesalces L.), and to the frequency of disturbances like fire and windthrow. A survey of 24 stands and in situ experimentation on Isle Royale show that balsam fir seedling survival is optimal under 40–79% canopy cover. Late-season and overwinter mortality in 1-year-old seedlings is highest under >80% canopy cover, while germination is lowest under

A B S T R A C T Measurements of transpiration resistance of Vaccinium myrtillus at various wind speeds indicate that this quantity is relatively insensitive to variations in wind speed in the range normally experienced under field conditions. The resistance is relatively low when compared with values reported in the literature for other plants. Placed in an identical environment, V. myrtillus plants from sunny sites were found to have measurably lower resistance and lower leaf temperatures than those from shady sites. Transpiration resistance appears to be inversely related to stomatal density. THIS INVESTIGATION of the transpiration resistance of the mountain blueberry Vaccinium myrtillus L. was made in connection with an ecological study of this plant in the Front Range of Colorado (Janke, 1968). One phase of the investigation was to determine how constant the transpiration resistance remains under the changing wind conditions which the plant normally experiences in the field. Another was to compare the transpiration resistance of plants found in the forest (shade plants) with those in the open (sun plants) under equivalent environmental conditions. Vaccinium myrtillus is a low shrub varying in height from 3-35 cm and spreading by horizontal rhizomes to form extensive clones. The leaves are small and elliptical, with an average length of 1.5 cm. In the Front Range of Colorado this species of blueberry comprises more than 95 % of the vascular plant ground cover in the sub

Measurable long-range effects of moose browsing were found in a boreal-type forest at Isle Royale National Park. Overall forest density decreased while average basal area per tree increased. Total basal area and reproduction density were unaffected. Balsam fir densities were drastically reduced, especially in younger age classes. For the most heavily used site, the oldest firs affected are linked to the time of moose arrival on Isle Royale. Mountain ash densities were also drastically reduced. White spruce, unpalatable to moose, increased in density, possibly due to reduced competition from fir. Birch and aspen densities were relatively unaffected. Their stems were mostly out of reach of moose when these animals first arrived. Reduction in fir and mountain ash densities accounts for the reduction in total tree density. Total cover in the shrub layer was unaffected by browsing, but averace stem height decreased. Taxus canadensis has almost disappeared on all browsed sites. Cover of low vascular plants and the ratio of windfalls to standing trees increased. INTRODUCTION The forests of Isle Royale National Park show several striking effects of moose (Alces alces andersoni) browsing. Many shrubs and tree saplings are truncated 1-1.5 m above the ,ground. Balsam fir (Abies balsamea) saplings appear scraggly and misshapen. Older firs exhibit a distinct browse line '2.5-3.5 m above the ground. Moose appear to be a maior ecological factor influencinz the successional development of the forest as well as the characteristics of the climax. The purpose of this study was to determine the extent of this influence. It is one phase of a comDrehensive research proiect aimed at investigating all maior aspects of the ecology of the upland boreal forest type in the park. It has been supnorted by the United States National Park Service and the Michigan Technological University. The effects of moose on a forest were studied by Berzerud and Manuel (1968) in the Noel Paul Drainage of Newfoundland where the forest type closely resembles that of Isle Royale. The emphasis in their study was on evaluating the effects on reproduction of tree sgecies and on determining the moose-carrying capacity of the area. Pimlott (1965) studied the effect of both moose and deer browsing upon major tree species in both Newfoundland and Anticosti Island. STUDY AREA Isle Royale National Park is an archipelago consisting of a large island about 72 km long and 14 km wide at its widest point and surrounded bv approximately 200 small islands. It lies in the western portion of Lake Superior 24 km SE of the Canadian shore and 72 km NW of Michigan's Keweenaw Peninsula. Uptilted layers of basaltic