Soil-nutrient relationships of tree species composition and dominance in the field irradiation gamma (FIG) area, Whiteshell nuclear research establishment, Pinawa, Manitoba

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Webb, Calvin James
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Seven nutrient parameters, hydrogen ion activity, calcium, potassium, phosphate, ammonium, nitrate, and organic matter, were measured in soil samples taken from a transect within the Field Irradiator-Gamma (FIG) area of the Whiteshell Nuclear Research Establishment, Pinawa, Manitoba. The relationship between these nutrients and the tree species composition and dominance of the overlying forest was interpreted using graphs and multiple linear regression equations. Four major vegetation associations were identified along the transect: 1) larch-black spruce, 2) black spruce, 3) balsam fir-black spruce, and 4) aspen. Most of the nutrient concentrations were highest in the soils of the first two communites, and lowest in the aspen association. The low concentrations in the latter were attributed to the early successional status of the vegetation and the sandy soil. Higher levels within the evergreen communities were probably due to the high cation exchange capacity of the peat soils and to base flow of nutrients. Concentration differences between the evergreen associations were believed to result from variations in the rate of decomposition of organic matter. Tree basal area appeared to be related to a cation complex consisting of organic matter, calcium, and to a lesser extent, potassium and ammonium. The prominence of these parameters, however, was dependent on the successional status of the vegetation and the depth of the soil sample.