Modulation of Diversity by Grazing and Mowing in Native Tallgrass Prairie

T. R. Seastedt, A. K. Knapp, Am. Nat. 141, 621 (1993); Blair J. M., Ecology 78, 2359 (1997).

Collins S. L., Ecology68, 1243 (1987).

A. K. Knapp and T. R. Seastedt in Grassland Dynamics: Long-term Ecological Research in Tallgrass Prairie A. K. Knapp J. M. Briggs D. C. Hartnett S. L. Collins Eds. (Oxford Univ. Press London in press).

D. C. Hartnett and P. A. Fay in (3).

S. J. McNaughton Ecol. Appl. 3 17 (1993)

F. B. Samson and F. L. Knopf BioScience 44 18 (1994).

Grime J. P., Nature242, 344 (1973); D. Tilman, Resource Competition and Community Structure(Princeton Univ. Press, Princeton, NJ, 1982); A. DiTommaso and L. W. Aarrsen, Vegetatio 84, 9 (1989).

This rate of N addition was chosen to add sufficient N to allow for a detectable plant response in a short period of time [J. D. Aber et al., Ecol. Appl. 3, 156 (1993)]. Studies have shown that supplemental N in this range was sufficient to affect productivity and community structure [T. R. Seastedt, J. M. Briggs, D. J. Gibson, Oecologia 87, 72 (1991); J. W. Silvertown, J. Appl. Ecol. 17, 491 (1980); Wedin D. A., Tilman D., Science 274, 1720 (1996)]. These accelerated responses are indicative of long-term cumulative effects of chronic elevated N deposition that occur in grasslands and other regions [P. M. Vitousek et al., Ecol. Appl. 7, 737 (1997)].

Spatially integrated photon flux density (0.4 to 0.7 μm; reported in micromoles per square meter per second) was measured with a 1-m ceptometer (Decagon) in four locations in each plot in September. Measurements were made at midday under clear sky conditions. Mowing occurred in late June of each year.

S. L. Collins, S. M. Glenn, Ecology 72, 654 (1991); Turner C. L., Knapp A. K., ibid 77, 1738 (1996).

L. C. Hulbert Prairie Scout 5 63 (1985).

In 1987 30 bison were reintroduced to Konza Prairie and the herd is now maintained at 200 individuals. Bison have unrestricted access to 10 watersheds subjected to different frequencies of late spring prescribed fire in a 1012-ha portion of prairie. This animal density was selected so that ∼25% of aboveground primary production is consumed annually.

Briggs J. M., Knapp A. K., Am. J. Bot.82, 1024 (1995).

10.1126/science.278.5344.1798

D. J. Gibson and L. C. Hulbert Vegetatio 72 175 (1987); S. L. Collins and E. M. Steinauer in (3).

R. Daubenmire Adv. Ecol. Res. 5 209 (1968)

R. J. Vogl in Fire and Ecosystems T. T. Kozlowski and C. E. Ahlgren Eds. (Academic Press New York 1974) pp. 139-194.

10.1126/science.273.5281.1555

S. L. Collins and S. M. Barber,Vegetatio 64, 87 (1985); Collins S. L., Glenn S. M., Gibson D. J., Ecology 76, 486 (1995).

F. Berendse M. J. M. Oomes H. J. Altena W. T. Elberse Biol. Conserv. 62 59 (1992); E. M. Steinauer and S. L. Collins in Prairie Conservation: Preserving North America's Most Endangered Ecosystem F. B. Sampson and F. L. Knopf Eds. (Island Press Washington DC 1996) pp. 39–52. The functional equivalency of bison and cattle grazing in North American grasslands remains uncertain [G. E. Plumb and J. L. Dodd Ecol. Appl. 3 631 (1993); (4)].

S. L. Collins and T. R. Benning in Biodiversity: A Biology of Numbers and Difference K. J. Gaston Ed. (Blackwell London 1996) pp. 253–280.

10.1126/science.277.5330.1296

10.1126/science.277.5325.500

Milchunas D. G., Sala O. E., Lauenroth W. K., Am. Nat.132, 87 (1988).

We thank J. H. Brown L. Gough J. H. Lawton S. J. McNaughton G. Shaver D. Tilman and P. M. Vitousek and four anonymous reviewers for comments on an earlier version of the manuscript. Supported by the NSF Long-Term Ecological Research Program Kansas State University and the Kansas Agricultural Experiment Station. Opinions expressed in this report do not necessarily reflect an endorsement by the National Science Foundation.