Proposed revision to Canadian System of Soil Classification: broaden taxonomic criteria for applying LFH horizons to include nonforest soils

Abstract

In the first edition (1974) of Canadian System of Soil Classification (CSSC), the taxonomic criteria for LFH organic horizons allowed application to any soil and land use developed under imperfectly to well-drained conditions. However, in the third edition (1998) of CSSC, the narrower taxonomic criteria for LFH horizons restricted application to only forest soils. A limited survey was conducted of some soil scientists across Canada to ask them if they had observed LFH horizons in nonforest soils. Distinct LFH horizons were observed across Canada under agriculture such as in no-till fields, tame and native pastures, and in reclaimed soils. They have also been observed in urban areas such as golf courses and grass-recreation fields. LFH horizons could also potentially develop under other nonforest land uses across Canada. Since no-till and native and tame pastures are most dominant in the prairies, the potential for LFH horizons is greatest in this region than elsewhere. However, they may occur anywhere in Canada where accumulation exceeds decomposition of organic material and they contain more than 17% organic carbon by weight or 30% organic matter. Therefore, we propose that the taxonomic criteria for applying LFH horizons be revised and broadened to include nonforest soils and be applicable to any soil order (where relevant) within Canada, and be at the discretion of the field pedologist. It is critical to identify and monitor LFH horizons over time because they are important for soil health, climate change, greenhouse gases, carbon sequestration, nutrient cycling, soil erosion, and hydrology.