EFFECT OF SPRING PRAIRIE BURNING ON HERBIVOROUS AND NON-HERBIVOROUS ARTHROPOD POPULATIONS

Purpose of the study was to quantitatively measure the effect of a single spring burning on biomass and density of arthropods in a native true prairie grassland. Triplicated sweep net collections with 200 sweeps per replicate were taken on four dates, both nighttime and daytime, on matched burned and unburned sites. The burned site produced significantly more total arthropods and greater biomass of arthropods. Cicadellidae and Tettigoniidae produced most of the increased numbers on the burned site and Acrididae and Tettigoniidae accounted for most of the increased standing crop biomass on the burned when compared to the unburned site. Significantly greater numbers and less biomass were found in daytime when compared to nighttime collections. Herbivore biomass on the burned site was significantly greater than on the unburned site while non-herbivore biomass was not significantly different be tween the burned and unburned sites. Fire is a commonly used tool in managing prairie rangeland in the central United States (Range Research Subcommittee 1962). Although considerable study has been devoted to determining effects of fire on autotroph production (e.g., see Ahlgren and Ahlgren 1960 or Mutch department of Biology, Kearney State College, Kearney, Nebraska 68847. Received for publication January 23, 1973. This content downloaded from 157.55.39.176 on Tue, 06 Dec 2016 19:36:51 UTC All use subject to http://about.jstor.org/terms 486 Journal of the Kansas Entomological Society 1970), little consideration has been given to the effects of fire on con sumer production. The purpose of this study was to quantitatively measure the effects of a single spring burning on the standing crop biomass and number of arthropods in a native true prairie rangeland. Burning effects were measured at two levels (herbivore and non herbivore) as well as total arthropods. Both nighttime and daytime sweep samples were taken so that arthropods active both night and day would be considered. Methods and Materials Sweep net collections were made at two locations in Donaldson Pastures near Manhattan, Kansas during the summer, 1969. These pas tures are located in the Flint Hills (true prairie). Nine separate pastures in Donaldson Pastures have been utilized for over 20 years to study the effects of stocking rate, deferred grazing and time of burning on the vegetation. I chose two-100 m diameter round plots, one located on an area which had not been burned for several years, the other about 100 m away on an area burned 10 April 1969 (but not burned in previous years). The areas were in different pastures but the stocking rate and grazing pressure (light to moderate grazing pressure by cattle) was essentially identical. Having the two areas in different pastures was desirable, because if the burned and unburned plots were in the same pasture, the cattle would have overgrazed the burned portion. The soil, topography and exposure of the two areas were similar and the botanical composition was almost identical before the spring burn ing (Table 1). Both sites were located on ordinary upland range sites. Collections were made every two weeks, beginning on 6 June 1969, and ending 27 August 1969. Three replicates of 200 sweeps were made with a 12-inch diameter net on each site between 1 and 3 PM and again between 12 and 2 AM. I alternated sites after each series of 200 sweeps. Sweeps were taken every three steps (circa 3 m) in circular transects throughout the plot, with each 100 sweeps making about two-360? circles through the plot. I attempted to sample all areas of the plot equally well with the 600 sweeps taken at each sam pling per site. After 100 sweeps, the net contents were emptied into cyanide jars. The samples were then frozen until sorted. The sweep samples were hand sorted from the litter and identified into 54 taxa (family or order). Number of arthropods in each taxon was determined and dry biomass (60? C, 48 hours) determined to the nearest 0.1 mg. Each taxon identified was classified according to feeding habits. Three categories were recognized: (1) herbivore, (2) non-herbivore (including predators, parasites, scavengers, non-feeders, etc.), and (3) mixed feeders (i.e., those taxa having both herbivorous and non This content downloaded from 157.55.39.176 on Tue, 06 Dec 2016 19:36:51 UTC All use subject to http://about.jstor.org/terms Vol. 46, No. 4, October, 1973 487 Table 1. Major plant species found on burned and unburned pastures before burning in April, 1969-1 Botanical Composition (%) Species Burned Unburned Andropogon gerardi 24.1 21.6 Andropogon scoparius 9.3 10.5 Sorghastrum nutans 10.9 10.7 Bouteloua curtipendula 6.2 9.6 Poa pratensis 13.3 14.3 Other perennial grasses 15.4 11.8 Annual grasses 0.4 1.7 Sedges and Rushes 6.4 6.2 Forbs 14.0 12.6 Shrubs 0.2 1.2