To estimate grasshopper densities in the patch-burn grazing experiment. Model response to grazing.
Location of Sampling Stations: Grasshopper density is determined on upland topographic locations. C3A, C3B, C3C, C1A, C3SA, C3SB, C3SC, C1B. 4 sits per watershed, 4 transects per site.
Frequency of Sampling: Grasshopper abundances are sampled once in late summer (August-September), with each site sample twice in a season a week apart.
Variable Measured: Number of individuals (categorized by instar) for individual grasshopper species.
Methods: Three watershed units (C3A, C3B, C3C) constitute "patches" that are alternately burned in a 3-year rotation within a single, fenced pasture (i.e., patch-burn grazing). Two additional watersheds are serving as controls: a grazed, annually/uniformly-burned watershed (C1A) and an ungrazed, annually/uniformly-burned watershed (1D).
Grasshopper sampling is done by standardized sweeping with canvas beating nets 38 cm in diameter. A sample of 250 sweeps (ten sets of 25 sweeps each) is taken at each site (4 independent sites per watershed) on each occasion. A sweep is taken at each step by traversing an arc of 1805 with the net through the top layer of vegetation. After 25 such sweeps, the contents of the net are emptied into individual plastic bags. Air is squeezed out and samples are kept on ice until they can be later frozen that same day. Samples are sorted and identified to species and instar at a later date. Samples are taken between 1000 and 1500 hours on clear, calm warm days: cloud cover is less than 50%, wind speed less than 24km/hr (15 mph), and ambient air temperature should be 25-40oC.
Sampling is replicated at each site a week apart. Sweep sampling methods follow those used for grasshopper sampling in the bison grazed watersheds. Sweeping effectiveness varies with site and season on Konza Prairie (e.g. sweeping is less effective on unburned prairie than on burned prairie). However, sweeping provides 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 tall grass prairie: night trapping vs. sweeping. Environmental Entomology 12: 1449-1454. Rarefaction calibrations determined that the cumulative species abundance curve reached an asymptote between 175-250 sweeps.
For additional metadata information see: http://lter.konza.ksu.edu/sites/default/files/DC.pdf
For additional methods information see: http://lter.konza.ksu.edu/sites/default/files/MM.pdf