Effects of hardwood reduction techniques on longleaf pine sandhill vegetation in northwest Florida

We tested whether the intensity of hardwood midstory reduction causes comme nsurate improvements of herbaceous groundcover in fire-suppressed Pinus pal ustris (longleaf pine) sandhills. Using a complete randomized block design, we compared the effects of three hardwood reduction techniques (spring bur ning, application of the ULW(R) form of the herbicide hexazinone, chainsaw felling/girdling) and a no-treatment control on plant species richness, and on life form and common species densities at Eglin Air Force Base, Florida , U.S.A., from 1995 to 1998. ULW(R) and felling/girdling plots were burned for fuel reduction two years after initial treatment application. We also s ampled the same variables in frequently-burned reference sandhills to estab lish targets for restoration. Spring bums achieved partial topkill of oaks (17.6-41.1% from 1995 to 1998) compared to reductions of 69.1-94% accomplis hed by ULW(R) and of 93.2-67.8% by felling/girdling treatments. We predicte d that plant species richness and densities of herbaceous groundcover life forms would increase according to the percent hardwood reductions. Predicti ons were not supported by treatment effects for species richness because po sitive responses to fire best explained increases in plant richness, wherea s ULW(R) effects accounted for the largest initial decreases. Legumes, non- legume forbs, and graminoids did not respond to treatments as predicted by the hypothesis. Again, positive responses to fire dominated the results, wh ich was supported by greater herbaceous densities observed in reference plo ts. Overall, we found that the least effective and least expensive hardwood midstory reduction method, fire, resulted in the greatest groundcover impr ovements as measured by species richness and herbaceous groundcover plant d ensities.