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Landscape Ecology

, Volume 28, Issue 7, pp 1293–1306 | Cite as

Small-scale patch structure in North American and South African grasslands responds differently to fire and grazing

  • Sally E. KoernerEmail author
  • Scott L. Collins
Research Article

Abstract

Fire and grazing significantly impact small-scale patch structure and dynamics in savanna grasslands. We assessed small-scale grass-forb associations in long-term fire and grazing experiments in North America (NA) and Southern Africa (SA). Transects of 128 0.25 m2 contiguous quadrats were sampled in areas with different combinations of grazing (ungrazed, single grazer, or multiple grazers) and fire frequency (unburned or annually burned). We predicted that (1) the patch structure of each of the dominant grasses in NA and SA would respond similarly to fire and grazing, and (2) that forb richness would be correlated to grass patch structure. Semi-variance analysis was used to determine patch structure of dominant grasses and forb cover. Community structure responded similarly in NA and SA to fire, grazing, and fire-grazing interactions. Species richness, diversity, and community heterogeneity were significantly higher in unburned-grazed sites. Grazing significantly increased forb cover and decreased cover of the dominant grasses, and the effects of fire on community structure depended on the grazing regime. Contrary to our prediction, we found that small-scale patch structure of the dominant grass species in NA and SA responded differently to grazing and fire. We found strong grass patch structure in unburned-ungrazed grasslands in both sites; however, grazing and fire reduced patch structure in NA but not SA, and in no instance did grass patch structure influence forb community structure. We conclude that fire and grazing have larger impacts on small-scale patch structure in NA than they do in SA even though overall community structure responded similarly on both continents.

Keywords

Dominance-diversity Grass-forb interaction Heterogeneity Konza Prairie Kruger National Park Semi-variance 

Notes

Acknowledgments

Thanks to M. Avolio, C. Chang, K. La Pierre, D. Burkepile, D. Thompson, L. Ladwig, D. Hoover, H. Archibald, A. Zimm, T. Morris, L. Calabrese, C. Reynolds, A. Walters, T. Schreck, A. Chaimberlin, and S. Hatmaker for assisting in the field and reviewing earlier versions of the manuscript and to Konza Prairie LTER and Kruger National Park. This research was supported by National Science Foundation (NSF; DEB-0841917), NSF Doctoral Dissertation Improvement Grant (DEB-0909912), University of New Mexico (UNM) Office of Graduate Studies (OGS) Student Resource Allocation Committee, UNM Biology Department Graduate Research Allocation Committee, UNM OGS Graduate Research and Project Travel Grant, UNM Biology Department Springfield Scholarship, and the UNM Biology Department Grove Research Scholarship.

Supplementary material

10980_2013_9866_MOESM1_ESM.docx (742 kb)
Supplementary material 1 (DOCX 743 kb)

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Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  1. 1.Department of BiologyUniversity of New MexicoAlbuquerqueUSA

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