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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Wetlands II
UNEXPECTED RESPONSES OF WOODLAND POND INVERTEBRATES TO MANIPULATIONS OF LEAF LITTER INPUT.
D.P. Batzer1 and B. Palik2. 1Department of Entomology, University of Georgia, Athens, Georgia 30602, 2USDA Forest Service, Forestry Sciences Lab, Grand Rapids, Minnesota 55744
Autumn leaf-fall is a conspicuous source of organic matter for woodland ponds, and similarly to headwater streams, litter is probably an important base of pond foodwebs. To test this hypothesis, we first described invertebrate assemblages in 66 woodland ponds of northern Minnesota, and related invertebrate richness and abundance to litter input. We, however, found that litter input was negatively rather than positively associated with invertebrate family richness across this set of ponds. We then selected 2 of the ponds, hydrologically split them into halves, and erected a mesh canopy over half of each pond to intercept leaf litter for 2 years. In one pond, overall invertebrate biomass and the biomass and abundance of some groups declined in the half-pond with reduced litter input, as would be expected. In the second pond, however, overall invertebrate biomass increased with litter reduction. In exclusion halves of both ponds, predators and sediment dwelling oligochaetes became more prevalent after 2 years of exclusion. We suspect that abiotic factors associated with litter superceded trophic factors to produce these apparently anomalous results. Leaf litter fall from trees might physically smother or chemically suppress some components of the invertebrate fauna in woodland ponds, at least over the short-term.
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