Wednesday, August 3, 2011

Oak Savannas

I have always been crazy about trees and have spent a lot of time in the last few years studying and painting trees. Here is some interesting information about Oaks Savannas.

Oak savannas once dominated a vast acreage in the prairie-oak transition. These forests have experienced significant decline primarily due to fire suppression and land use changes. The oak savannas of today represent only 0.02% of the original range making them the most endangered community in the prairie. Oak savannas are areas dominated by low-density oak trees with an understory consisting of a diverse array of grass and herbaceous species. The historical fire regime in these systems was frequent low intensity underburns occurring every 2-12 years that consumed primarily the grass understory. Climate and ungulate migration may have also been determining factors in the expanse of these systems. Savanna oaks and the accompanying understory have adaptations that help them withstand fire, drought, and other disturbances. Fire suppression has resulted in forests with closed canopies, which limits oak regeneration while favoring favoring more shade tolerant hardwoods. Along with this change there has been an increase in litter layers, decreased species diversity, and decreased savanna wildlife.  Restoration is the primary means to reintroduce these systems. Oak savanna restoration requires reducing canopy cover to change structure and reintroducing fire to restore process. Often additional treatments are needed when prescribed fire proves to be incapable at reducing canopy density. Regardless of the restoration process, the oak savanna has to be continually managed to ensure regeneration. Restoring these ecosystems leads to an increase in understory heterogeneity and a unique assemblage of oaks and savanna species.


Linda Blondheim

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