Current address: USDA Forest Service, Pacific Northwest Research Station, 1133 N. Western Ave., Wenatchee, WA 98801, USA; E-mail email@example.com
Plant functional group responses to fire frequency and tree canopy cover gradients in oak savannas and woodlands
Article first published online: 24 FEB 2009
2007 IAVS - the International Association of Vegetation Science
Journal of Vegetation Science
Volume 18, Issue 1, pages 3–12, February 2007
How to Cite
Peterson, D. W., Reich, P. B. and Wrage, K. J. (2007), Plant functional group responses to fire frequency and tree canopy cover gradients in oak savannas and woodlands. Journal of Vegetation Science, 18: 3–12. doi: 10.1111/j.1654-1103.2007.tb02510.x
Nomenclature: Barkley (1986).
- Issue published online: 24 FEB 2009
- Article first published online: 24 FEB 2009
- Received 8 February 2006; Accepted 27 August 2006
- Cedar Creek Natural History Area;
- Disturbance ecology;
- Fire ecology;
- Prescribed fire;
- Savanna restoration;
- Woody plant
Questions: How do fire frequency, tree canopy cover, and their interactions influence cover of grasses, forbs and understorey woody plants in oak savannas and woodlands?
Location: Minnesota, USA.
Methods: We measured plant functional group cover and tree canopy cover on permanent plots within a long-term prescribed fire frequency experiment and used hierarchical linear modeling to assess plant functional group responses to fire frequency and tree canopy cover.
Results: Understorey woody plant cover was highest in unburned woodlands and was negatively correlated with fire frequency. C4-grass cover was positively correlated with fire frequency and negatively correlated with tree canopy cover. C3-grass cover was highest at 40% tree canopy cover on unburned sites and at 60% tree canopy cover on frequently burned sites. Total forb cover was maximized at fire frequencies of 4–7 fires per decade, but was not significantly influenced by tree canopy cover. Cover of N-fixing forbs was highest in shaded areas, particularly on frequently burned sites, while combined cover of all other forbs was negatively correlated with tree canopy cover.
Conclusions: The relative influences of fire frequency and tree canopy cover on understorey plant functional group cover vary among plant functional groups, but both play a significant role in structuring savanna and woodland understorey vegetation. When restoring degraded savannas, direct manipulation of overstorey tree canopy cover should be considered to rapidly reduce shading from fire-resistant overstorey trees. Prescribed fires can then be used to suppress understorey woody plants and promote establishment of light-demanding grasses and forbs.