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Catalytic Potential of Mor Humus Layers as an Indicator of Biological Activity¹

ABSTRACT

Knowledge of the degree of biological activity of holorganic soil layers is essential to foresters for three reasons: It influences the rate of forest growth, the intensity of silvicultural cuttings, and the choice of biodegrading material for amelioration of nursery soils impaired by eradicants. Information on this attribute of humus layers was obtained by manometric determination of their catalytic potentials (Cp). Biologically inert humus layers, associated wih retarded release of nutrients and depressed growth of forest stands yielded catalytic potentials within the range of 4 to 35 mm of mercury. On the other hand, many thick, so-called "raw humus" layers exhibited high biological activities expressed by catalytic potentials from 103 to 139. Such layers were confined to forest stands of high site indexes indicating no deleterious retardation of nutrient cycling.

¹ Contribution from Dep. of Soil Science, Univ. of Wisconsin, Madison, WI 53706. Research supported by the College of Agric. and Life Sciences, Univ. of Wisconsin, and the Wis. Dep. of Natural Resources.

² Lecturer, Professor, and Professor Emeritus, respectively.

Received for publication April 26, 1979. Accepted for publication August 2, 1979.