RELATIONSHIPS BETWEEN CASTS OF GEOPHAGOUS EARTHWORMS (LUMBRICIDAE, OLIGOCHAETA) AND MATRIC POTENTIAL .1. CAST PRODUCTION, WATER-CONTENT, AND BULK-DENSITY
Rp. Hindell et al., RELATIONSHIPS BETWEEN CASTS OF GEOPHAGOUS EARTHWORMS (LUMBRICIDAE, OLIGOCHAETA) AND MATRIC POTENTIAL .1. CAST PRODUCTION, WATER-CONTENT, AND BULK-DENSITY, Biology and fertility of soils, 18(2), 1994, pp. 119-126
Laboratory experiments were conducted to investigate the effects of ma
tric potential on the rate of cast production, and water content and b
ulk density of casts. Fresh, subsurface, and surface casts were collec
ted from Aporrectodea caliginosa, A. rosea and A. trapezoides kept in
reconstituted soil cores at matric potentials between -25 and -2 kPa.
Rates of cast production and water contents of fresh casts, subsurface
casts, and surface casts increased as the matric potential of soil co
res increased from -25 kPa to -2 kPa. The bulk density of fresh casts
decreased as the matric potential of soil cores increased from -8.6 to
-2 kPa. Aestivating earthworms were found in soil cores at all matric
potentials except -2 kPa. The rate of cast production at the drier ma
tric potentials may have been related to the water balance of the eart
hworms. As the matric potential of the soil cores decreased, the amoun
t of water egested per cast remained constant, but overall the water e
gested per day decreased due to a reduction in the number of casts pro
duced. Differences between the three species were identified in rates
of cast production, with A. rosea generally producing more casts than
either A. caliginosa or A. trapezoides, and in water contents and bulk
densities of fresh casts.