patch-burn grazing

PBG02 Aboveground primary productivity within permanent and rotating grazing exclosures 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. This data set includes measurement of aboveground net primary productivity based upon end-of-season standing crop biomass (grams per square meter) of live graminoids, forbs, woody plants, and previous year's dead vegetation within permanent (“ungrazed”) and rotating (“grazed) sections of grazing exclosures to determine long term effects of bison grazing on aboveground primary production. The permanent section of the exclosure is fixed, while the movable section is rotated every 6 years among the four possible compass coordinates relative to the fixed section. Exclosures were erected in 2010 in all PBG watersheds. However, C3SA/C3SB/C3SC did not have a history of grazing, and sampling did not begin in those watersheds until 2012. Therefore, the “grazing” treatments in those watersheds were not previously, and should be interpreted as reference data until the movable sections are rotated into grazed areas in 2015.

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To determine long-term effects of cattle grazing on aboveground primary production.


Location of Sampling Stations: There are four exclosures on Florence soils and four exclosures on Tully soils in each of the following grazed watersheds: N01a, N01b, N04a, N04d (total=32). Exclosures in N01a and N04a were erected in March,1988 and were first sampled in 1992. Exclosures in N01b and N04b were erected in April, 1992 and were first sampled in 1995.

Frequency of Sampling: Once per year at peak biomass (September to October).

Variable Measured: Aboveground biomass of grass, forbs and woody and p.dead.

Methods: An exclosure is 5 m x 10 m and constructed of fence posts and sturdy cattle paneling. One half (5 m x 5m) has been designated as the permanently ungrazed treatment; it has not been grazed since 1988 (N01a and N04a) or 1992 (N01b and N04d). It is marked with pink poles. The other half is the grazed section; it is marked with blue poles. Every six years a new grazed area is closed off and animals will not have access to this section for six years. At the end of six years, this section will be reopened to grazing and a new section is closed off. The grazed section moves in a clock-wise pattern around the permanently ungrazed section.

Sampling methods are identical to PAB01 except five 0.1m2 plots randomly located within each section, grazed vs. ungrazed; total 10 samples per exclosure. Grazed and ungrazed sides of the exclosure are clipped at the same time. The plant biomass for each clipped plot is bagged, dried at 60° C and weighed. Samples are not kept for further analysis.

Summary of Changes:

2010: All pens were constructed in spring 2010. Two pens per watershed. Pens 1-8 (0c3a, 0c3b, 0c3c, 0c1a) were sampled in 2010.
2011: Pens 9-16 (c1sb, c3sa, c3sb, c3sc) were constructed in 2010, but not sampled until 2011 because cattle were not introduced.
2016 (March): grazed sections of pens 1-8 were moved 90° clock-wise
2017: Grazed section of pens 9-16 moved 90° clock-wise
2021 (December): Moved grazed sections of pens 1-8, 90° clock-wise. Installed carabiner clips in one corner to allow for easier and safer entry into pens.
2022 (November): Moved grazed sections of pens 9-16, 90° clock-wise. Installed carabiner clips in one corner to allow for easier and safer entry into pens.

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