Oak decline across the Ozark Highlands- from stand to landscape and regional scale processesThis article is part of a larger document. View the larger document here.
Oak decline has been a problem in forests of the Ozark Highlands (OzH) for decades. It has impacted upland oak-hickory forests, particularly species in the red oak group (Quercus section Lobatae) across the Ozark Highlands of Missouri, Arkansas, and Oklahoma. The oak decline complex is often described in terms of predisposing factors, inciting factors, and contributing factors. Drought is a common inciting factor in oak decline, while advanced tree age is considered a predisposing factor, and opportunistic organisms such as armillaria root fungi and wood boring insects are believed to contribute to the decline and demise of formerly stressed trees. Declining trees are initially indicated by foliage wilt and browning followed by progressive branch dieback. If crown dieback continues, trees can die. In this paper we synthesize four of our key research studies on oak decline, examining the occurrence, distribution, and characteristics of oak decline as it has impacted the OzH across space and time. Long-term climate forecasts for this region indicate decreasing precipitation and warming temperatures. Consequently, periodic droughts such as the widespread 2012 U.S. drought are expected to increase in frequency and intensity, and thereby exacerbate oak decline on millions of hectares of aging oak forests. Results from our research indicate that regular monitoring of forest conditions; increasing the proportion of species in the white oak relative to the red oak group; judicious application of prescribed fire; periodic thinning to favor species in the white oak group; and proactive harvest of aging red oak species anticipated to be at increased risk of mortality are methods that can help forest managers mitigate oak decline.