A dendrochronological examination of a recent decline of chestnut oak across southern Indiana

Abstract

Oak (Quercus) species are a major component of much of the eastern forest. Unfortunately, multiple species have experienced well-documented episodes of decline and mortality over the past century. A mortality event in chestnut oak (Q. prinus) across southern Indiana in 2016 sparked concern about the health of chestnut oak, leading to an effort to identify factors that triggered and contributed to the event. We evaluated stand conditions, tested for the presence of Phytophthora cinnamomi, and collected tree cores from chestnut oak trees within diseased stands and nearby healthy stands. We found no evidence that P. cinnamomi was associated with mortality. Instead, our dendrochronological analysis suggests that a series of dry June conditions followed by wet March conditions weakened vulnerable trees, allowing the exceptional drought in 2012 to incite decline. Greater basal area increment prior to growth decline, along with a higher probability of decline on mesic north-northeastern slopes, suggest that vulnerable individuals may have been those that preferentially allocated carbon into above ground growth at the expense of developing drought resilient root systems.