OOS 15-9
Disturbance on the western edge of the eastern deciduous forest
Braun’s “Deciduous Forests of Eastern North America” describe the forested vegetation of a biome that covers a vast area, east of the grasslands of the Great Plains to the Atlantic coast. Capturing the range in species, vegetation types, and physiographic characteristic in such a broad area represents a staggering accomplishment on Braun’s part. That there might be limited depth in coverage of some regions within the Deciduous Forest Formation should be expected given the breadth. The Oak Hickory forest region that centers on the Ozark and Ouachita Mountains with oak hickory as the late successional forest of the western, represents the driest area of the EDF, and it may be argued that this forest is the most dissimilar to the character of the other EDF regions.
Results/Conclusions
What is now referred to as the oak hickory forest is much broader than that originally proposed by Braun. The current area subsumes the original oak pine, oak chestnut and the oak hickory forests of Braun’s organization. There is little reason that these should be coalesced given the differences in composition, structure and disturbance regimes. Less mesic conditions in the Interior Highlands and substantial evidence of fires conjoin the Great Plains and the western edge of the EDF. For the western edge of the oak hickory system - the Ozark interior highlands- the importance of fires in affecting forest dynamics has been well documented. More recently we have assessed the importance of wind events in structuring the forest. Disturbance regimes reconstructed from the past 400 years confirm a general higher frequency of disturbance events, principally fire and wind, than most forests of the EDF. Furthermore, we have identified a unique synergism of fire and wind. Despite relatively frequent fires in some areas (e.g. fire interval of <6 years), wind events also served as a means for tree species compositional change.