A new microcosm approach to litter decomposition studies

Abstract

Microcosms, simplified analogues of natural ecosystems, are a useful tool for studies of litter decomposition. A literature review shows that if microcosms are carefully constructed to mimic nature accurately, they allow researchers to control and independently vary normally covarying environmental factors (temperature, moisture, soil animals) that influence decomposition rates, while maintaining a sufficiently natural situation so that results of laboratory tests may be extrapolated to the field situation with confidence. A simple, inexpensive system of laboratory microcosms for decomposition studies is described and evaluated in this paper. The microcosm, housed within an airtight PVC chamber, consists of a litter layer overlying a core of forest floor strata collected with a minimum of disturbance to physical structure and populations of soil organisms. The microcosms have been tested with soil and litter from an aspen woodland and a pine forest, at temperatures ranging from −6 to +26 °C, and have been maintained in the laboratory for up to 6 months without significant deterioration. The microcosm system provided decomposition estimates that were precise, replicable, and rapidly obtained by measuring either mass loss or CO2 efflux from litter samples. Problems with the method include rapid increases in populations of some soil animals, difficulty in controlling relative humidity, and acceleration of decay rates compared with those in litter in the field.