Effects of eastern redcedar on prescribed fire and fire modeling in cross timbers forests

Eastern redcedar (Juniperus virginiana; ERC) has encroached into Cross Timbers forests, an ecotone historically dominated by post oak (Quercus stellata) and blackjack oak (Q. marilandica) and the transition from the eastern deciduous forest to the Great Plains. Since the early 20th century, less fire has caused shifts toward fire intolerant species, altering site conditions. ERC presence can result in increased fuel load and has become an important management focus. Cross Timbers forests historically relied on fire for continued oak dominance, so increased fuel loading due to ERC is pertinent for management. Mechanical treatment of large ERC is necessary since ERC is less susceptible to fire mortality at larger sizes. We performed a forest and fuels inventory followed by common mechanical treatments of ERC in Oklahoma Cross Timbers forests. We followed this with a prescribed burn to assess how forest, fuels, and ERC management conditions affect fire behavior. The presence of dead, dry ERC fuels resulted in increased flame lengths and more severe fire behavior while removal of ERC fuels lowered fire behavior. Untreated stands of ERC encroached Cross Timbers forests may have lower flame lengths and fire severity due to the loss of fine fuels associated with heavy ERC encroachment. ERC treatment affects fire behavior. Furthermore, there is a lack of studies on fire prediction in ERC encroached forests. Our fuels and prescribed fire weather conditions data were used to model simulated fire conditions in FlamMap and BehavePlus. A visually best match fuel model from Scott and Burgan (2005), a custom fuel model using our fuels data, and the currently used model to predict fire behavior in ERC encroached Cross Timbers forests were compared. Overall, fire programs performed poorly at predicting site specific flame lengths but in limited cases, fuel models could be associated with ERC treatment to predict fire behavior on average and at a landscape scale. ERC in Cross Timbers forests alter fire behavior, and depending on management goals, treatments can negatively affect fire behavior and forest structure. Fire modeling of fuel types incorporating ERC encroachment needs further development.