Restoration and Maintenance of Oak Savannas

Oak savannas are sustainable under specific conditions: adequate rainfall, average grazing disturbance, and moderate fire frequency under which trees are isolated to fire free areas. Under intermediate conditions oak savannas are persistent in the long term (Jeltsch et al. 1996). In order to restore and maintain oak savannas the conditions of  frequent fire and moderate soil disturbance must be fulfilled.

There are two strages for oak savanna restoration: short-term and long-term management. The short-term involves reducing canopy cover quickly by applying thinning techniques to restore the structure of the historical savanna to canopy cover between 5-30%, although the definitions of adequate canopy cover vary (Faber-Langendoen 1995). Long-term management focuses on restoring the function to the system by reintroducing a periodic low intensity fire regime.

Restoring oak savannas using prescribed burning is a long-term commitment to an appropriate fire regime (Peterson and Reich 2001). The goal is to use fire to reduce shrub cover and increase grasses and then allow fire free intervals sufficient to regenerate new cohorts of oaks (Peterson and Reich 2001). High intensity fires may be necessary during the course of restoration to decrease unwanted woody species (Faber-Langendoen 1995). High fuel loads are often a problem and may require manual reduction or several low intensity burns (Hartman 2001). Decreases in litter depth will occur over successive burns and litter will become more irregular across the landscape. Despite fuel reduction burns, fuels in small size classes may increase and cause more intense fires until an open canopy state is achieved and a grass component replaces the down woody debris (Hartman 2001). Over time the ecosystem will re-equilibrate with the defining process fire, and management can move into the maintenance phase. This phase will maintain a dynamic equilibrium between overstory oak mortality and reproduction.

Site selection is important in restoring oak savannas. Management should be focused on sites that occur within the historic range of oak savannas. Sites selected should also have remnant species in the understory that were found in historical oak savannas such as pyrogenic grasses and native legumes and asters found in the adjacent prairie communities.

Native animal populations will generally benefit from the reductions in tree canopy and increased open understory following restoration, but care must be taken to assure populations are unaffected by increased prescribed fire. Arthropods on the whole are unaffected by changes in fire frequency over a thirty year period; however certain groups of arthropods may experience declines in their populations (Siemann et al. 1997). Avian populations respond variably to restoration using prescribed fire in oak savannas. There is an overall increase in ground and bark feeders while a decrease is seen in upper canopy feeders. A number of birds that are associated with open canopy conditions increase in abundance due to reintroduction of fire (Table 5) (Davis et al. 2000). The increase in standing dead trees and decline in tree densities are the primary reasons for the abundance of bird species (Davis et al. 2000). Further research on the impacts of restoration fire on native plant and animal communities is important to completely understand their population densities and fluctuations.

One important aspect in restoration of the oak savannas includes research to fully understand the scope of their ecological niche. Although some information exists on oak savanna restoration, as noted by Henderson and Epstein (1995), we still lack a complete understanding of these ecosystems, and the techniques needed to restore them. Future scientific research is needed to  better understand endemic species and their needs, longer term maintenance, and the role of prescribed fire and ungulate populations in oak savannas.