Response of ground layer vegetation cover and richness two years after burning and thinning on the Southern Cumberland Plateau

Background/Question/Methods

Prescribed burning and thinning cause changes in the cover and richness of ground layer vegetation by altering light levels and forest floor properties. The ground layer is especially important for its high levels of biodiversity, importance to wildlife, and interaction with tree regeneration. We examined the response of ground layer vegetation cover and richness to four treatments: burning, thinning, thinning and burning, and an untreated control. The study area is located in the William B. Bankhead National Forest in northeastern Alabama and consists of 20-50 year old pine-hardwood stands dominated by planted loblolly pine (Pinus taeda). We report on the change in cover and richness of vascular plants (≤1.4 m height) two growing seasons post-treatment. We sampled a total of 80 m² in each of eight stands at five plots per stand. We determined percent foliar cover of each vascular species in the ground layer vegetation on 16 m² per plot. We also estimated area occupied for ground-level characteristics such as pine and broadleaf litter, down woody debris (where the diameter >2.5cm), tree bole, mineral soil, nonvascular plants, and logging roads.

Results/Conclusions

Our analyses indicated that overall cover increased with burning (p=.04) and thinning (p<.01). A combination of burning and thinning significantly increased cover (p<0.01) compared to the change in cover in control plots. Stands that were both burned and thinned experienced an increase in cover compared to stands that were thinned but not burned (p<0.01) and stands that were burned but not thinned (p<0.01). Both graminoid (p<0.01) and vine cover (p<0.01) increased with thinning as well as a combination of burning and thinning (p<0.01). There were no significant changes in forb cover over the treatments. Overall species richness did not change significantly following any of the treatments. Results of this study indicate that burning and thinning do promote ground layer vegetation growth in the second year following treatment.