Document: JAR-3-68-10

Effects of fire intensity on shrub resprouting in pine savanna.

THAXTON, J.M.* and W.J.PLATT

Louisiana State University, Baton Rouge, LA 70803, U.S.A. ¹

Abstract:
We manipulated pre-fire fuel loads in an upland longleaf pine (Pinus palustris) savanna to test the hypothesis that local variation in fire intensity affects post-fire resprouting patterns of shrubs. Transects were established across elevational gradients from upper slopes to ravines along intermittent streams in a second growth savanna containing both native and exotic shrub species. Shrub species composition and ramet density were determined in randomly selected 1m² plots within transects both before and 2 months after early growing season fires in spring 1999. Prior to the fires each plot was randomly assigned one of four fuel load treatments. Treatments consisted of fine fuel removal, pine needle addition, wood addition and control. During fires, maximum fire temperatures were recorded in each treatment plot. Maximum fire temperatures were significantly higher in pine needle and wood addition plots than in control or fuel removal plots. For all species pooled, post-fire stem density was significantly lower in needle addition and wood addition than in control plots. Stem density did not differ significantly between fuel removal plots and control plots. Post-fire stem density was reduced below that of pre-fire levels only for wood addition plots. Patterns to the post-fire resprouting of individual species appeared to be related to the morphology of underground resprouting organs. While post-fire stem density of all species tended to be reduced in needle addition and wood addition plots relative to control plots, these effects were more pronounced for species that resprout from root crowns. Also, post-fire densities for both native and exotic root crown species tended to be reduced below pre-fire levels in both needle addition and wood addition plots. Post-fire densities of rhizomatous species differed among some treatments but tended to be significantly higher than pre-fire densities. These results suggest that local variation in fire intensity as a result of heterogeneous fuel loads may affect shrub community dynamics in pine savannas. Furthermore, the response of shrub species to fire intensity variation may be somewhat predictable as a function of the morphology of their underground organs.

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This abstract is being presented at: 5:00 PM in session:
Oral Session #35: Fire Ecology.