PURPOSE
Long-term monitoring of dynamics of species composition and abundances in grasshopper assemblages associated with varying frequency of fire.
LOCATION OF SAMPLING STATIONS (two replicate sites per treatment, all sites ungrazed)
020B - unburned Florence soil A: grid O-28 B: N-28 020B - unburned Tully soil A: N-29 B: N-29 001D - annual burn Florence soil A: T-24 B: R-27 001D - annual burn Tully soil A: T-28 B: S-28 004B - 4 year burn Florence soil A: H-28 B: F-27 004B - 4 year burn Tully soil A: G-28 B: F-28 002D - 2 year burn Florence soil A: V-26 B: U-24 002C - 2 year burn Florence soil A: L-29 B: L-31 004D - 4 year burn Florence soil A: K-29 B: J-28 004F - 4 year burn Florence soil A: Q-28 B: P-28 004G - 4 year burn Florence soil A: R-28 B: R-30 010D - 10 year burn Florence soil A: R-27 B: Q-28
FREQUENCY OF SAMPLING
Varied among years. Since 1988, sites have been sampled twice (on different dates) in late July to early August. In addition to such sampling, sites were also sampled at various earlier dates in 1982-1987.
VARIABLES MEASURED
Number of individuals (categorized by instar in 1982-1988) for individual grasshopper species.
METHODS
Sampling is done by sweeping with canvas beating nets 38 cm in diameter. A sample of 200 sweeps (ten sets of 20 sweeps each) is taken at each site on each occasion. A sweep is taken at each step by traversing an arc of 180o with the net through the top layer of vegetation. After 20 such sweeps, the contents of the net are emptied into plastic bags. These samples are subsequently frozen until grasshoppers are removed and identified to species and instar. All samples are taken between 1000 and 1500 hours on clear, calm, warm days: cloud cover should be less then 50%, winds less then 24 km/hour (15 mph), and ambient air temperature should be 25-40oC.
Sweeping effectiveness varies with site and season on Konza Prairie (e.g. sweeping is less effective on unburned than on burned prairie). However, sweeping does provide good estimates of relative abundances of individual species present at any one place and time on both burned and unburned prairie. For more information, consult: Evans, E. W., R. A. Rogers, and D. J. Opfermann. 1983. Sampling grasshoppers (Orthoptera: Acrididae) on burned and unburned tallgrass prairie: night trapping vs. sweeping. Environmental Entomology 12: 1449-1454.
In 1985, additional watersheds (002D, 004D, 004F, and 010D) were added to the sampling regime for early August to provide more long-term data on the influence of fire frequency on grasshoppers. Watershed 004G was added in 1986. Sampling on watersheds to be grazed (N01B, N04D, and N20B) was discontinued in 1985/ Sampling in June and early July, 1986 was reduced to watersheds 001D, 004D, 010D, and 020B only; too few grasshoppers are collected by sweeping in the first half of the summer for all watersheds to merit sampling. In 1987, sampling in June and early July was restricted to sites 001D, 002C, 004B, and 004F.
Beginning in 1985, sweeping was restricted to all sites being sampled (twice, on different dates) in late July to early August. Only upland sites on ungrazed watersheds are sampled.