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Soil micropore structure and carbon mineralization in burrows and casts of an anecic earthworm (Lumbricus terrestris)

Summary: Soil micropore structure and carbon mineralization in burrows and casts of
an anecic earthworm (Lumbricus terrestris)
Josef H. GoÈrres, Mary C. Savin, Jose A. Amador*
Laboratory of Soil Ecology and Microbiology, 024 Coastal Institute, University of Rhode Island, Kingston, RI 02881, USA
Received 22 June 1999; received in revised form 8 February 2001; accepted 8 March 2001
Anecic earthworms (those that build semipermanent vertical burrows) are known to alter the biological activity and physical structure of
soils through their burrowing and casting. Information on how earthworms change the physical structure of soil may provide clues about the
mechanisms by which earthworms affect microbial processes such as nutrient mineralization. We evaluated the pore structure of bulk soil and
of the soil in burrows and casts formed by an anecic species of earthworm (Lumbricus terrestris) in a fallow ®eld. Differences in pore
structure (speci®c pore volume, Vsp, and median pore neck dia., D) were assessed using mercury intrusion porosimetry. We also examined the
relationship of these physical properties with mass water content at ®eld capacity (um), rate of C mineralization (Cmin) and speci®c C
mineralization rate (Csp Cmin/C content of soil). Mean values of Vsp (^SD) for bulk, cast and burrows were 242 ^ 35, 213 ^ 13, and
197 ^ 4 ml g21
, respectively. Values for D were (^SD) 10.8 ^ 2.5, 7.9 ^ 3.3, and 5.5 ^ 2.9 mm for bulk, burrow, and cast soil, respectively.
A smaller proportion of the pore volume in cast and burrow soil was associated with pore diameters in the 3±30 and 30±100 mm range than in
bulk soil. um was higher in burrow and cast soil than in bulk soil and was inversely proportional to Vsp and D. Cmin and Csp followed the order:
burrow .cast . bulk soil. Both Cmin and Csp decreased inversely with Vsp. By contrast, no consistent relationship was observed between
either measure of C mineralization and D. Our results suggest that the changes in soil pore structure produced by anecic earthworms cause a
shift towards smaller pore volume and smaller pore neck diameters. These changes in turn affect physical (e.g. water retention) and microbial


Source: Amador, José A. - Department of Natural Resources Science, University of Rhode Island


Collections: Environmental Management and Restoration Technologies; Environmental Sciences and Ecology