Red Oak Decline and Mortality by Ecological Land Type in the Missouri Ozarks

Oak decline, the precipitous mortality of mature oak trees, has been a chronic problem in xeric oak ecosystems and is reaching unprecedented levels in red oak group (Quercus section Lobatae) species in the Ozark Highlands. The high rates of mortality are leading to rapid changes in species composition, forest structure, and related changes in fire risk, insect populations, and colonization patterns of root diseases such as Armillaria. Based on intensive analysis of more than 455 half-acre plots of the Missouri Ozark Forest Ecosystem Project (MOFEP), we compared red oak mortality change by ecological land types (ELT) using a multiple comparison test. There were significant differences in red oak mortality between certain ELTs. Using ANCOVA, we found that the abundance of red oak species was a major contributor; stand structure and tree attributes played a marginal role. The result is helpful for interpreting the landscape-scale change of red oak decline and mortality.