Localized dynamics of earthworm populations in relation to bison dung in North American tallgrass prairie
1992
James, S.W.
Potential interactions between earthworms and the large mammal Bison bison include effects of dung deposition and effects of grazing via plant responses to defoliation. In the experiment reported here I sought to test the hypothesis that populations under dung pats increase primarily by immigration from adjacent areas, and secondarily by reproduction. A 1.25 m2 grid of 100 bison dung pats of uniform composition was placed on a level upland area of tallgrass prairie in Kansas in October 1987. Baseline data collected in 1986 in the same manner from the same site were used to measure the influence of dung pats. The April 1988 wet preserved biomass of Aporrectodea turgida under dung pats was ten times the intra-grid non-pat sample values, and was triple the baseline measures. Biomass remained greater under pats through October 1988 but declined to baseline by April 1989. Octolasion cyaneum biomass had a less dramatic increase under dung pats and quickly equilibrated between pat and non-pat samples. Diplocardia kansensis and D. longiseta had consistently higher biomass under pats than non-pat samples. D. smithii and unidentified juvenile Diplocardia were not affected by dung application. Demographic profiles and gut content analysis suggest that A. turgida, D. longiseta and D. kansensis immigrate and consume dung. The latter is in accord with previous estimates of the feeding ecology of these species.
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