Volume density of earthworm burrows in compacted cores of soil as estimated by direct and indirect methods

J. R. Hirth, B. M. McKenzie, J. M. Tisdall

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)

Abstract

After earthworms of the species Aporrectodea caliginosa and A. rosea had burrowed in compacted cores of soil for 68 days the cores were sectioned horizontally. The upper surface of each sectioned layer of soil was photographed before it was dissected and the dimensions of all burrows within the layer measured. Volume densities calculated from the direct measurement of burrows were compared with the values calculated by stereology from data obtained from two image analysis methods, computerised image analysis and point counting with a systematic lattice. The assumption implicit in all stereology calculations was satisfied for this experiment in that the burrows of both species showed no preferred orientation in the compacted soil. Computerised image analysis could not measure the density of all burrows in the photographs because of the lack of contrast between cast- filled burrows and the soil and the complex shapes of the burrows. Although the volume densities of A. caliginosa burrows calculated from point counts were correlated with the values calculated from direct measurement, point counting over-estimated volume densities by two to three times. In the experiment, A. rosea produced too few air-filled burrows for the lattice to detect. The relative ratios of air-filled to cast-filled burrows calculated from the point counts suggested that approximately two-thirds and eight- ninths of the burrows of A. caliginosa and A. rosea, respectively, were filled with casts.

Original languageEnglish
Pages (from-to)171-176
Number of pages6
JournalBiology and Fertility of Soils
Volume21
Issue number3
DOIs
Publication statusPublished - Feb 1996

Keywords

  • Aporrectodea species
  • Earthworm burrows
  • Earthworm casts
  • Image analysis
  • Point counting
  • Volume density

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