North- and south-facing slopes were chosen as sites for this study because of the great environmental and vegetational differences shown for such slopes in other studies (Potzger 1939, Shanks & Norris 1950, Cantlon 1953). Microenvironmental and vegetational sampling was carried out from March 17 to November 3, 1957. Data were obtained from 17 slopes, 9 north-facing and 8 south-facing. Slopes ranged from 31-60% in angle and deviated not more than 20 degrees from true north or true south. Vegetation was sampled on 16 of these slopes, but microenvironmental data were recorded for only 4 north and 4 south slopes.
Although efforts were made to minimize all variables with the exception of topographic orientation, they were not entirely successful. In addition to orientation, an important variable was the presence or absence of protection as afforded by a facing slope. Thus, 4 groups of slopes were available: protected north slopes, open north slopes, protected south slopes, and open south slopes. The following data summarize the specific topographic characteristics of the sample sites:
Protected north slopes (Stations 1, 5, 6, 10, 16). Station 1 was on the side of an esker facing into a kettle whereas Stations 5, 6, 10, and 16 were on the sides of kettles. Contours at all stations were concave.
Open north slopes (Stations 8, 11, 13, 15). Station 8 was on the side of a large kettle but, as the opposite side was over 500 ft distant, the facing slope offered no protection. Stations 11 and 15 were on the edge of an outwash fan and Station 13 was on the side of an esker. Contours at Stations 8 and 11 were concave and those at Station 13 were straight. Contours at Station 15 were slightly convex.
Protected south slopes (Stations 7, 14). Both of these stations were on the sides of kettles with concave contours.
Open south slopes (Stations 2, 3, 4, 9, 12, 17). These stations were all on the sides of eskers. Stations 2 and 12 actually faced into a large kettle but, as the opposite slope was approximately 500 ft distant, there was no real protection. Contours at Stations 2, 3, and 12 were essentially straight. At Stations 4 and 9 contours were slightly convex whereas at Station 17 contours were somewhat concave.
Although no historical data were available for the sample sites, it appeared that there had been no selective effects of grazing or lumbering on any slope or group of slopes. Thus, it was assumed that the microclimatic and vegetational differences recorded were the results of real habitat differences rather than the past cultural practices of man.
Vegetational sampling was carried out during July and August of 1957. On each of the 16 slopes sampled a plot 900 m2, consisting of three tiers of three 100 m2 plots, was laid out. Subplots with IDs 1-3 are in the bottom tier, 4-6 in the middle tier, and 7-9 in the top tier. Presence of all vascular plant species occurring in each subplot was recorded. Coverage of species in the field layer (within 4.5 feet of the ground) was determined by the line-intercept method. As plots were laid out on the horizontal and plant cover was recorded on the horizontal by means of two meter sticks arranged so that one was placed perpendicular to the horizontal and the other moved up or down along it until it was horizontal. The central 10 m of both diagonals of each of the subplots were measured with this device. Thus, 180 m of line-intercept data were available for each slope sample plot. The diameter at breast height of all trees over 1 inch d.b.h. and density of all shrubs and transgressives below 1 inch d.b.h. and over 4.5 ft high were determined in each subplot. In addition, the total canopy cover of species over 1 inch d.b.h. was determined by pacing the four 30 m across-slope boundaries of the 3 tiers of subplots. The life-form of all species encountered was determined from winter and summer field observation during a part of 1956 and all of 1957 and by consulting other life-form studies of similar areas (Ennis 1928, McDonald 1937). Voucher specimens of all species are deposited either in the Reserve herbarium or in the author's collection. Nomenclature is that of Fernald (1950). Representative leaves were chosen from the voucher specimens and their areas determined both by tracings on millimeter graph paper and by the 2/3 length times width rule of Cain et al. (1956). The entire species list, showing both lifeforms and leaf-size, may be found in Cooper (1958).
