Estimating increased fuel loading within the Cross Timbers forest matrix of Oklahoma, USA due to an encroaching conifer, Juniperus virginiana, using leaf-off satellite imagery

Encroachment of eastern redcedar (ERC; Juniperus virginiana) into the Quercus dominated Cross Timbers region of the Southern Great Plains is an ongoing management issue that affects ecosystem services and wildfire hazard. The location and density of ERC in the forest understory and midstory are important information for fire managers seeking to estimate the behavior of fires or anticipate resources and attack methods needed to contain wildland fires. We developed a method to use remotely sensed, 3-band, satellite imagery to determine ERC presence and abundance within the Cross Timbers forest on 90 Bureau of Indian Affairs Trust Land properties in Pawnee and Payne Counties Oklahoma, USA. We used 130 (0.04 ha) field verification plots to establish the accuracy of the technique and estimate the biomass of the highly flammable ERC to determine the additional fuel loading that ERC encroachment represents. Compared to the field measurements, the satellite imagery identified approximately 50% of the ERC canopy area ([Actual Canopy Area] = 1.9517 * [Classified Canopy Area] + 13.093, r(2) = 0.78, n = 124). The relationship between ERC canopy area and ERC aboveground biomass was also determined ([Biomass (kg)] = 4.1839 * [Actual Canopy Area] - 72.206, r(2) = 0.71 n = 124). Estimating the biomass of the 90 larger tracts (10-65 ha) based on ERC canopy area, we calculated that ERC canopy cover averaged 21% within the forest matrix and that ERC biomass averaged 6.3 Mg ha(-1) which represents a 38% increase in available fuel loading due to ERC encroachment. The addition of the highly flammable, evergreen ERC to the fuel load of the Cross Timbers forest likely increases the potential of wildfire damage. Our results can be used throughout the Cross Timbers region of Texas, Oklahoma, and Kansas, in coordination with fuel and fire simulation models, to inform management related to wildfire and fuel reduction treatments.