Soil invertebrates are concentrated on roots

Abstract

The density of invertebrates on roots and in soils was determined. This is the first time such observations have been reported; they were made by direct observation through windows of the Soil Biotron at the University of Michigan Biological Station, Pellston, MI. The Soil Biotron is located in a Bigtooth Aspen-mixed hardwood stand on a sandy podzol. Horizontal transects in the top eight cm of soil were censused through a 50 power dissecting microscope mounted on a trolley. Light from the microscope did not affect behavior of the invertebrates. The roots were principally Bigtooth Aspen (Populus grandidentata) and Bracken (Pteridium aquilinum). Total area of soil censused in July was 262 cm2, 3037 cm2 in August, and 446 cm2 in October, 1988. Invertebrate density was at least two orders of magnitude greater on roots than in the surrounding soil (Fig. 1). Invertebrate groups with highest density on roots were bacterivores (Enchytraeidae), microbivores (Tydeidae, Oribitida, Collembola), and fungivores (Protura). Predatory Mesostigmata were least concentrated on roots. The food of Pauropoda is unknown, but they consistently occurred at root tips.