Forest Microclimate: A Topographic Study in Ontario

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Abstract
To rate the effect of topography on surface microclimate daily observations were made May through September 1955 at 12 points along a cleared strip (1500 ft. long, 200 ft. wide) extending north-south across a ridge 140 ft. high. Comparative observations were made at 4 points on a similarly shaped ridge under forest cover. Daily maximum air temperature on the south facing slope averaged 0.5[degree]C higher on the forested ridge than on the cleared ridge. Comparing, observations from different points on the cleared ridge: monthly averages of daily maximum air temperature (1 ft. above ground level) were consistently higher (by 1[degree]C) on the north slope than on the south; four-inch soil temperatures were higher on the south slope than on the north; Piche evaporation was highly correlated with ground elevation of the observation point and inversely correlated with air temperature, which shows that local wind speed was the operative factor. The anomaly in air temperature is shown to follow from lower evapo-transpiration on the north slope of the cleared ridge than on the south. The proportion of incoming radiational energy absorbed as latent heat of evaporation is shown to be a major determinant of temperature at and near the soil surface. Associated observations of phenology of plants and radial growth of dominant pine trees are reported.