L. Provencher et al., Effects of hardwood reduction techniques on longleaf pine sandhill vegetation in northwest Florida, RESTOR ECOL, 9(1), 2001, pp. 13-27
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.