Exotic herbivores and fire energy drive standing herbaceous biomass but do not alter compositional patterns in a semiarid savanna ecosystem
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AbstractQuestionsFire regime alterations are pushing open ecosystems worldwide past tipping points where alternative steady states characterized by woody dominance prevail. This reduces the frequency and intensity of surface fires, further limiting their effectiveness for controlling cover of woody plants. In addition, grazing pressure (exotic or native grazers) can reinforce woody encroachment by potentially reducing finefuel loads. We investigated the effects of different fire energies on the herbaceous plant community, together with mammalian wildlife herbivory (exotic and native combined) exclusion, to inform best management practices.LocationTexas semiarid savanna, southern Great Plains, USA.MethodsWe conducted an experiment in which we manipulated fire intensity and herbivore access to herbaceous biomass in a splitplot design. We altered fire energy via fuel addition rather than applying fire under different environmental conditions to control for differences in standing biomass and composition attributable to differential plant physiological status and fire season.ResultsHighenergy fire did not reduce herbaceous biomass or alter plant community composition, although it did increase amongplot variability in composition and forb biomass relative to lowenergy fire and nonburned controls. Grazing pressure from native and nonnative mammalian herbivores reduced aboveground herbaceous biomass regardless of fire treatments, but did not alter community composition.ConclusionsManagers seeking to apply highintensity prescribed fire to reduce woody encroachment will not negatively impact herbaceous plant productivity or alter community composition. However, they should be cognizant that repeated fires necessary for greatly reducing woody plants in heavily invaded areas might be difficult to accomplish due to finefuel reduction from wild herbivores. High fencing to restrict access by wildlife herbivores or culling might be necessary to build fuels sufficient to conduct highintensity burns for woodyplant reduction.
Preiss, V. D., Wonkka, C. L., McGranahan, D. A., Lodge, A. G., Dickinson, M. B., Kavanagh, K. L., ... Rogers, W. E.
complete list of authors
Preiss, Virginia D||Wonkka, Carissa L||McGranahan, Devan A||Lodge, Alexandra G||Dickinson, Matthew B||Kavanagh, Kathleen L||Starns, Heath D||Tolleson, Douglas R||Treadwell, Morgan L||Twidwell, Dirac||Rogers, William E
