Tue, Aug 03, 2021:On Demand
Background/Question/Methods
Forest stands composed of varying mixtures of softwood and hardwood species (gymnosperms and angiosperms, respectively) are an important component of forest ecosystems across the southern USA. This complex of forest communities is commonly referred to as mixed pine/hardwood. Currently, there are concerns about declines in the amount of forest land area in this type. Much of the decline can be attributed to cutting/management practices that favor pine but also infestations such as southern pine beetle, and diseases such as fusiform rust. I used empirical data from the USDA Forest Service, Forest Inventory and Analysis (FIA) program to monitor the changes in the softwood/hardwood type between two measurement periods. Arkansas was chosen for this case study. The analysis was based on a measurement of approximately 3500 sample units in 2005 and a remeasure of these same sample units in 2015. Forest stands were evaluated by categorizing each sample unit by its proportion of stand basal area (BA) in softwoods or hardwoods (for trees ≥2.56 cm). Ten classes were established in the data reduction phase: 0-10 percent of BA in softwood, 11-20 percent in softwood, and so on. The reciprocal of each class represented the hardwood proportion (0-10 softwood = 91-100 hardwood).
Results/Conclusions Across Arkansas there were approximately 6,211,093 (±49,689 C.I.) ha of forest land remeasured in both forest inventory measurements. I arbitrarily labeled the 0-10 and 91-100 percent softwood classes as pure hardwood or pure softwood types, respectively so only stands composed of 11-90 percent in softwood were considered for analysis of the mixed softwood/hardwood type. Between the 2005 and 2015 measurement periods mixed softwood/hardwood stands decreased by 201,740 ha. This was 6.6 percent of all remeasured forest land that was in the mixed softwood/hardwood type in 2005. Of the 8 percent-classes in the mixed softwood/hardwood type, 6 classes decreased in area, while the 11-20 and 41-50 percent classes increased. In contrast, the pure softwood and hardwood types changed accordingly; the 91-100 percent softwood class increased 28.8 percent in forest land area between 2005 and 2015 while the 0-10 percent softwood class (91-100 percent hardwoods) decreased 2.6 percent. This illustrates possible forestry management practices that favor pine over hardwoods. A harvested mixed softwood/hardwood stand is often replaced with a pure pine plantation, a practice that gradually eliminates the mixed softwood/hardwood type stands over time. Describing and documenting baseline states of ecosystem components is an important first step in ecosystem risk assessment.
Results/Conclusions Across Arkansas there were approximately 6,211,093 (±49,689 C.I.) ha of forest land remeasured in both forest inventory measurements. I arbitrarily labeled the 0-10 and 91-100 percent softwood classes as pure hardwood or pure softwood types, respectively so only stands composed of 11-90 percent in softwood were considered for analysis of the mixed softwood/hardwood type. Between the 2005 and 2015 measurement periods mixed softwood/hardwood stands decreased by 201,740 ha. This was 6.6 percent of all remeasured forest land that was in the mixed softwood/hardwood type in 2005. Of the 8 percent-classes in the mixed softwood/hardwood type, 6 classes decreased in area, while the 11-20 and 41-50 percent classes increased. In contrast, the pure softwood and hardwood types changed accordingly; the 91-100 percent softwood class increased 28.8 percent in forest land area between 2005 and 2015 while the 0-10 percent softwood class (91-100 percent hardwoods) decreased 2.6 percent. This illustrates possible forestry management practices that favor pine over hardwoods. A harvested mixed softwood/hardwood stand is often replaced with a pure pine plantation, a practice that gradually eliminates the mixed softwood/hardwood type stands over time. Describing and documenting baseline states of ecosystem components is an important first step in ecosystem risk assessment.