Evolution of burrow systems after the accidental introduction of a new earthworm species into a Swiss pre-alpine meadow |
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| Authors: | Y Capowiez A Pierret P Monestiez L Belzunces |
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| Institution: | (1) Laboratoire de Toxicologie Environnementale, INRA Zoologie, 84914 Avignon, Cedex 09, France e-mail: capowiez@avignon.inra.fr, FR;(2) Land and Water, CSIRO, Canberra, Australia, AU;(3) INRA Biométrie, 84914 Avignon, Cedex 09, France, FR |
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| Abstract: | The unintentional introduction of a new earthworm species (Aporrectodea nocturna) into a Swiss pre-alpine meadow resulted in a great increase in earthworm density in the newly colonized area (386 m–2) compared with the density observed in the natural area (273 m–2) where an earthworm community was already present. To investigate the impact of this introduction on the burrow systems,
eight soil cores (length 25 cm, diameter 16 cm) were taken (four in the colonized area and four in the natural area) and analysed
with computer-assisted X-ray tomography. The resulting images were processed to obtain the 3D-skeleton reconstructions of
the earthworm burrow systems. Due to high variability in these burrow systems, only slight differences were observed between
the two areas. The total burrow length and the mean burrow lengths tended to be greater in the colonized area. Moreover, the
distribution of pore numbers with depth showed different patterns with a maximum for depths between 10 cm and 15 cm in the
colonized area and a maximum for depths between 20 cm and 25 cm in the natural area. These differences may have been related
to: (1) the particular behaviour of A. nocturna, which was observed to cast at the surface in this site, and (2) the predominance of juvenile earthworms around the colonization
front. These differences were sufficient to create significant effects on the continuity of the burrow systems (assessed by
the number of different pathways between virtual horizontal planes) for the two areas. The colonized area was characterized
by a greater pore continuity, which could have resulted in enhanced transfer properties.
Received: 2 July 1999 |
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| Keywords: | Colonization Aporrectodea nocturna Three-dimensional skeleton Computer-assisted X-ray tomography Earthworm burrow system |
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