Towards a Taxonomic Classification of Humus Forms

Washington D.C.

1993

49 S.

52 Lit. Ang.

Bandaufführung

7380

64684

A two-category taxonomic classification and a methodology for field description are proposed to aid in consistent identification and interpretation of humus forms for ecosystem research, surveys, and management. The classification uses the nomenclature principles of the U.S. soil taxonomy and the master organic horizon designations of the Canadian system of soil classification. It includes humus form taxa that have been recognized in Europe and North America. Recognized taxa are defined on the basis of observable and easily measurable morphological properties. Three taxa, Mor, Moder, and Mull, are recognized at the order level and are differentiated according to the type of F horizon and the relative prominence of organic-enriched A horizons. These reflect principal differences in the nature and rate of decomposition processes. Names of the 16 taxa at the lower, group level are created by adding formative elements to the name of the order. For example, groups of the Mor order are differentiated according to the relative thickness of F and H horizons (Hemimors and Humimors); degree of humufication in the H horizon (Resimors); content of decaying wood (Lignomors); and moisture regime (Hydromors, Fibrimors, and Mesimors). Phases can be formed for any taxon to recognize important morphological properties that deviate from the taxonomic differentiae. Keys to the recognized taxa and descriptions of representative humus form profiles for each group are provided to assist in identification. Methods for describing, sampling, and surveying humus forms are presented to facilitate field examinations and subsequent studies.