EVALUATION DES CRITÈRES DE DIFFÉRENCIATION POUR LA CLASSIFICATION DE 92 MATÉRIAUX TOURBEUX DU QUÉBEC ET DE L’ONTARIO

Abstract

In order to evaluate the differentiation criteria for classification of organic soils, 92 peat-like materials have been characterized according to criteria generally used by the Canadian Pedological Commission (C.P.C.). The botanical composition and the Ca:Mg ratio have been added to these criteria. A close relationship was found (r = −0.865**) between the pyrophosphate indices obtained by the method adopted by C.P.C. and those measured using the Kaila method. The distribution of peat-like materials which are classified as fibric, mesic and humic was different depending on whether the differentiation criterion used was rubbed fibre or pyrophosphate index. A classification using the first criterion gives a dominant mesic population, while the second criterion favored the fibric group. The curvilinear relationship obtained between the content of rubbed fibres and the pyrophosphate index shows that the degree of decomposition measured by these criteria was proportional only for materials which are fundamentally fibric or humic. The mesic group is more or less well-defined by the two criteria. The botanical composition proved to be the most discriminatory differentiation element. Also, a previous grouping of the materials according to this criterion would ensure a more orderly and efficient utilization of the other characterization criteria, and would provide a better-defined differentiation of the mesic materials.