A QUANTITATIVE STUDY OF THE MICROÖRGANIC POPULATION OF A HEMLOCK AND A DECIDUOUS FOREST SOIL

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Abstract
Monthly quantitative examinations were made of virgin hemlock and deciduous forest soils in the New York Botanical Garden, New York City, from January through June, 1930, and from October, 1930, through March, 1931. Topsoil (litter, fungous and true humus layers) and subsoil (first mineral layer) were examined, and the accepted technique for quantitative analyses was used. An increase in numbers of organisms was found with an increase in soil moisture and with freezing of the soils; neither slight changes in pH nor differences in air temp. seemed to affect the numbers. They decreased with depth; this might be due partly to lack of organic matter in the subsoil. Without exception, seasonal maxima came in April. In hemlock topsoil fungi outnumbered bacteria and actinomycetes. Bacteria predominated in the deciduous topsoil and in both subsoils; actinomycetes were scarce in all soils (probably due to acid character[long dash]pH range, 4.3-5.7). In hemlock topsoil, during January, February and March, there was an increase in Citromyces, particularly, and of the Peni-cillium group in general, with a corresponding decrease in Trichoderma. The opposite was true in the fall months. These data were obtained from macroscopic observation of plates. Members of the order Mucorales and of the genus Aspergillus were scarce.