big bluestem

PBG04 Reproductive effort of Big Bluestem, Indiangrass and Little Bluestem in the Patch-Burn Grazing Experiment at Konza Prairie


'PBG' datasets are associated with a long-term, large-scale study that is addressing the effects of fire-grazing interactions in the context of a Patch-Burn Grazing management system designed to promote grassland heterogeneity. Effects of patch-burn grazing management on plant and animal diversity and the nature and variety of wildlife habitat are being assessed in two replicate management units, each consisting of three pastures (watersheds) designated C03A/C03B/C03C and C3SA/C3SB/C3SC. In each patch-burn grazing unit, one watershed is burned and two that are left unburned in a given year. The burning treatments are rotated annually so that each pasture is burned every third year. Each patch-burn grazing unit is paired with an annually-burned pasture for comparison with traditional grazing systems (C01A and C1SB). All grazing units are stocked with cow/calf pairs from approximately 1 May until 1 Oct at a stocking density equal to 3.2 ha per cow/calf. To examine the impact of patch burning and grazing in all 8 units, we monitor changes in plant species composition, residual biomass, grassland bird populations, insect populations, small mammal populations, soil nutrients, and stream water quality1 (1C3SA/C3SB/C3SC unit only). The KSU Department of Animal Science monitors cattle performance, including weight gain and body condition to assess the economic feasibility of using patch-burn management on a widespread basis. PBG041 includes data on flowering stem height (m) of three dominant prairie grasses: Andropogon gerardii (ANGE), Sorghastrum nutans (SONU), and Schizachyrium scoparium (ANSC). PBG042 includes flowering stem density (no. per sq. m) and mass (grams per sq. m) for the same grass species.

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To estimate seed reproduction, flowering stem mass, height, and population densities of three dominant prairie grasses: Andropogon gerardii (ANGE), Sorgastrum nutans (SONU), and Schizachyrium scoparium (ANSC) in the Konza Prairie LTER watersheds.


Location of Sampling Stations: Florence and Tully locations of un-grazed watersheds: 001d, R01a, R01b, 002c, 002d, 004a, 004b, 020b, R20a, R20b, 0SpA, 0SpB, 0SuA, 0SuB, 00FA, 00FB, 00WA and 00WB. Sampling is done 2-3 m away from the permanently marked species composition transect (see PVC maps)

Frequency of Sampling: Once per year at the time of seed maturation (Oct to Nov).

Variable Measured: 1. Flowering stem heights (in centimeters); 2. Density of flowering stems (No. per m2); 3. Weight of flowering stems (g per m2)

Methods: Because these measurements involve destructive sampling, no permanently marked plots were set up. All samples are taken 2-3 m parallel to the permanently marked species composition plots at each LTER site.

Individual flowering stem heights: A quasi-random walk is initiated adjacent to the permanent LTER transects during which 25 sampling points per transect (100/LTER treatment) are located at intervals of about 2 m. At each sampling point, the stem height for the nearest (no more than 1m from observer) flowering individual of each of the three species is measured to the nearest cm. Mean flowering stem height is calculated for each species at each site from the 100 values.

Density and weight of flowering stems: Along a transect parallel to the permanent LTER plant species composition transects but on the opposite side from where the PAB biomass collections for the year have occurred, six 0.25 m2 plots (50cm x 50cm) per transect (x4 transects = 24 per site) are sampled. Each plot is 3 m from the species composition marker and 10 paces from the next plot. Within each of these plots, the number of flowering stems of each species is counted and the stems are clipped at ground level, bagged by species, oven dried at 60oC, and weighed. The density of flowering stems (No. per m2) and the mean biomass of flowering stem (g per m2) are calculated for each species.

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