Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

Published source details Callaham Jr. M.A., Blair J.M., Todd T.C., Kitchen D.J. & Whiles M.R. (2003) Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass. Soil Biology & Biochemistry, 35, 1079-1093.
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Summary

Responses of soil-dwelling invertebrates to tallgrass prairie management by fire and grazing are poorly known. A study conducted at Konza Prairie Biological Station in Kansas (central USA), examined the effects of annual fire, mowing and nutrient additions on density and biomass of belowground macroinvertebrates (earthworms and herbivorous insects).

Treatments commenced in 1986 as part of longer-term studies. In 12 x 12 m plots, treatments applied were: annual spring burning or unburned; mowing and raked annually in early July or unmowed; and no nutrients added, 10 g N/m² added as ammonium nitrate, 1 g P/m² as super-phosphate, and both N and P added. There were four replicates of each of the 16 treatment combinations.

Soil macroinvertebrates were sampled in 1994 (three weeks in October) and 1999 (one week in June). North American earthworms were identified to genus and non-native European earthworms to species when possible. Arthropods were identified to family or genus. Invertebrate biomass was estimated as ash-free dry mass (AFDM).

There were various interactions and possible synergistic effects of treatments on invertebrate communities and species but some general trends were evident.

European earthworms (Aporrectodea spp. and Octolasion spp.) were commonest in unburned plots (e.g. Aporrectodea c.14 individuals/m² in unburned + P addition, 3/m² burned + P addition). The proportion of earthworm biomass comprising native genera was 75% or higher in burned, mowed plots. That of non-native species was greater in unburned, unmowed, and fertilized plots. This suggests that lack of traditional disturbance/management (i.e. fire and grazing) may make soils more susceptible to increased abundance of European earthworms. Also in plots where non-natives were most prevalent, displacement of native species may be occurring.

Nymphs of two Cicada genera were collected: Cicadetta spp. was abundant in burned plots (mowing reduced abundance); Tibicen spp. occurred almost only in unburned plots. Treatment effects on herbivorous beetle larvae (families Scarabaeidae, Elateridae and Curculionidae) varied, but nutrient addition (N or P) plots tended to support greater densities, and mown plots usually lower densities.

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