Did you know that fire regime alterations are pushing open ecosystems worldwide past tipping points where alternative steady states characterized by woody dominance prevail. The intensity and frequency of surface fires are reduced, limiting their effectiveness for controlling cover of woody plants. Grazing pressure can also reinforce woody encroachment by potentially reducing fine-fuel loads.
The study below was conducted in semi-arid savanna Texas and the southern Great Plains of the United States. In this study, the effects of different fire energies on the herbaceous plant community, together with mammalian wildlife herbivory (exotic and native combine) exclusion, were investigated to stipulate what the best management practices were.
An experiment was conducted where fire intensity and herbivore access to herbaceous biomass in a split-plot design was manipulated. Fire energy via fuel addition was altered. This was done 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.
The results indicated that high-energy fire did not reduce herbaceous biomass or alter plant community composition. However, there was an increase among-plot variability in composition and for biomass relative to low-energy fire and non-burned controls. The grazing pressure from native and non-native mammalian herbivores reduced the above-ground herbaceous biomass regardless of fire treatments, although it did not alter community composition.
The conclusions of the study showed that managers seeking to apply high-intensity prescribed fire to reduce woody encroachment will not negatively impact herbaceous plant productivity or alter community composition. However, repeated fires in heavily invaded areas might be difficult to accomplish due to fine-fuel reduction from wild herbivores.
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Preiss, V. D., Wonkka, C. L., McGranahan, D. A., Lodge, A. G., Dickinson, M. B., Kavanagh, K. L., Starns, H. D., Tolleson, D. R., Treadwell, M. L., Twidwell, D., & Rogers, W. E. (2023, October 20). Exotic herbivores and fire energy drive standing herbaceous biomass but do not alter compositional patterns in a semiarid savanna ecosystem. Wiley Online Library. https://onlinelibrary.wiley.com/