Plant functional group responses to fire frequency and tree canopy cover gradients in oak savannas and woodlands.

Abstract

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. Understory 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 percent tree canopy cover on unburned sites and at 60 percent tree canopy cover on frequently burned sites. Total forb cover was maximized at fire frequencies of 4 to 7 fires per decade, but was not significantly influenced by tree canopy cover. Cover of nitrogen-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 understory plant functional group cover differs among plant functional groups, but both play a significant role in structuring savanna and woodland understory vegetation.

Citation

Peterson, D.W.; Reich, P.B.; 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(1): 3-12