DISTRIBUTION AND ABUNDANCE OF BURROWS FORMED BY LUMBRICUS-TERRESTRIS L AND APORRECTODEA-CALIGINOSA SAV IN THE SOIL-PROFILE

The distribution of burrows made by Lumbricus terrestris L. and Aporre ctodea caliginosa Sav. was studied on an unploughed field. The positio ns of earthworm burrows were mapped in 9 horizontal planes to a depth of 80 cm in a pit of 70 by 40 cm. Burrow diameter and presence of plan t roots growing in burrows were also recorded. Burrows on six of the n ine planes were considered as two-dimensional point patterns and analy zed as spatial point processes. A three-dimensional image was construc ted for burrows formed by L. terrestris. The total number of burrows r anged between 180 and 1260 m(-2) at depths of 80 and 30 cm, respective ly. The majority of burrows were evidently formed by A. caliginosa. Th e smallest size class (2-3 mm) of burrows was dominant at depths betwe en 8 and 40 cm. Deeper in the soil profile, the proportion of larger b urrows increased markedly. Burrows formed by L. terrestris appeared to be non-branching, and extended vertically beyond 80 cm. In all soil l ayers studied, burrow distribution was found to be completely random. The proportion of burrows containing plant roots was between 18 and 60 %, at depths of 80 and 15 cm, respectively. (C) 1997 Elsevier Science Ltd.