Risk factors of oak decline and regional mortality patterns in the Ozark Highlands of Arkansas and Missouri

Since the late 1970s, oak decline and mortality have plagued Midwestern-upland oak-hickory forests, particularly species in the red oak group (Quercus Section Lobatae) across the Ozark Highlands of Missouri, Arkansas, and Oklahoma (Dwyer and others 1995). 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 red oak borers are believed to contribute to oak decline and mortality. Declining trees first show foliage wilt and browning followed by progressive branch dieback in the middle and/or upper crown. Trees eventually die if crown dieback continues. Our objective was to analyze oak mortality by species group and inventory year to illustrate the general spatial and temporal trends of oak decline and mortality by using data from the Forest Inventory and Analysis (FIA) Program of the Forest Service, U.S. Department of Agriculture; specifically, we used the 1999�2006 annualized data from FIA plots in the Ozark Highlands of Arkansas and Missouri.