Fire frequency and mosaic burning effects on a tallgrass prairie ground beetle assemblage

Published source details Cook W. & Holt R. (2006) Fire frequency and mosaic burning effects on a tallgrass prairie ground beetle assemblage. Biodiversity and Conservation, 15, 2301-2323.
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Summary

Fire frequency has significant effects on the flora and fauna of North American tallgrass prairies. Concern has been expressed that widespread annual burning (a traditional management technique), sometimes in combination with intense livestock grazing, negatively impacts prairie ecosystems. A common recommendation is thus to create a landscape with a mosaic of different burn regimes.

This study investigated the effects of fire frequency (annual, 4-year burn and 20-year burn rotations) in tallgrass prairie on carabid ground beetles, a key group within the prairie arthropod community. Focusing on whether mosaic burning facilitates beetle diversity at a grassland study site in Kansas, USA.

Study site: The study was undertaken at the Konza Prairie Biological Station, eastern Kansas, USA. The site consists of 3487 ha of tallgrass prairie.

Burns: Prairie landscape units were burned every 1, 4, or 20 years, and in a fourth season across the range of vegetative structure to assess the variability of the carabid community within the study area.

Pitfall trapping: Pitfall trapping (using 9 cm diameter, 7 cm deep, plastic cups, placed just below ground level, half-filled with dilute ethylene glycol, covered with plywood to exclude rain) was conducted over three seasons (16 August to 15 November 1997; 12 May to 14 November 1998; 8 May to 1 November 1999).

In 2000 whether vegetation structure heterogeneity (e.g. presence of woody vegetation) affects beetle community composition was investigated. In 2001, to assess whether there were transitory pulses in community composition driven by localized disturbance, beetle communities across stark (but temporary) habitat boundaries was investigated by pitfall sampling in adjacent burned and unburned landscape units from 2 weeks before to 8 weeks after the burn.

A total of 22,477 individuals (1,818 in autumn 1997, 11,632 in1998, 6,192 in1999, 859 in 2000, and 2,077 in 2001) of 29 carabid species were collected.

Fire frequency had only a small effect on ground beetle diversity, and most abundant species were observed widely across habitat and management types.

Aggregate specimens captured and species richness for 1997–1999 was:

1-year burn rotation - 5,852 individuals, 16 species
4-year burn rotation - 7,535 individuals, 20 species
20-year burn rotation - 6,255 individuals, 18 species

Fire frequency effects were apparent primarily in changes in abundance of common species. Colonization of burned areas appeared not to occur from non-burned areas, but from underground or from long distances.

These results suggest that widespread annual burning of tallgrass prairie remnants may not have dramatic effects on prairie carabid beetles, but the authors urge caution regarding the application of the results to other taxa within tallgrass prairies.

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