Management practices in tallgrass prairie: large- and small-scale experimental effects on species composition

Published source details Gibson D.J., Seastedt T.R. & Briggs J.M. (1993) Management practices in tallgrass prairie: large- and small-scale experimental effects on species composition. Journal of Applied Ecology, 30, 247-255.
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Summary

The Flint Hill region of north-eastern Kansas, USA is one of the few surviving unploughed areas of tallgrass prairie, due to steep slopes and rocky terrain. The area has been traditionally managed by cattle grazing and hay-making. Prescribed burning is undertaken to maintain high production levels and keep out woody species. The effects of contrasting management practices on the species composition of tallgrass prairie in Kansas, USA were examined at two spatial scales. In the study described here the effect of burning and mowing in large-scale plots was investigated.

Study site: The study was undertaken on the Konza Prairie Reseach Natural Area, in the Flint Hills Region of Kansas, USA. Dominant plant species include warm season grasses (C₄): big bluestemAndropogon gerardii, little bluestem A.scoparius and Indian grass Sorghastrum nutans; common forbs include heath aster Aster ericoides, western ragweed Ambrosia psilostachya and western mugwort Artemesia ludoviciana.

Management treatments The effects of 12 years of mowing and burning on five soil types (Tully, Irwin, Sogn, Plorence and Benfield) reflecting a topoedaphic gradient were examined in 45 large-scale plots (200 x 50 m) of 10,000 m². No livestock grazing took place during this period. Burning was initiated in 1972 and mowing in 1974.

Burn treatments were - April burn at 1-, 2- and 4-year intervals; annual burning at 3 seasons (March, late April and November); unburned control.

Mowing treatments were - cutting in March, July or November, with hay left or removed, dependent on treatment.

Plant monitoring: In late spring, mid-summer and late summer 1983, percentage cover of all vascular plants was recorded in 20 circular 10 m² sample plots within each of the large-scale plots.

Soil type was shown to be the most important discriminator of plant communities. Burning separated plots at the second level of classification and mowing effects were not apparent until the third level of resolution. As management treatments, burning and mowing differed in their effect on species richness, especially the representation and number of exotic species. Mowing allowed the incursion of exotic species (e.g. Causican bluestem Andropogon (Bothriochloa) bladhii).

The number of native species was significantly lower on annually burned plots on lowland Tully soil compared with unburned or July-mown plots. Mown plots had a higher cover of cool season (C₃) grasses, annual grasses, and annual/biennial forbs, and also a greater number of annual grasses and exotic species.

Conclusions: Overall, soil type proved the principal factor in discrimination of vegetation types. In this context, burning was of secondary importance, and mowing had least impact. However management influenced abundance and species richness within the vegetation life-form groups.

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http://links.jstor.org/sici?sici=0021-8901%281993%2930%3A2%3C247%3AMPITPL%3E2.0.CO%3B2-T