Death and Taxus: the contribution of mechanical damage to the multiple factors associated with Taxus brevifolia mortality

Recent increases in tree mortality are often attributed to climate, but climate extremes may just be the last of many stressors that have unfolded over many years resulting in tree death. Potentially it is only those trees weakened by mechanical damage or attacks by insects or fungi that are susceptible to climate-mediated mortality, whereas vigorous trees resist periods of unfavorable climate. Although previous studies have explored immediate and catastrophic effects of mechanical damage via blowdowns and stem breakage, few have investigated the delayed effects of mechanical damage on mortality. Taxus is a shade-tolerant genus of subcanopy trees or shrubs distributed throughout the northern hemisphere. Populations of Taxus are in decline worldwide but owing to the tenacity of Taxus in the face of stressors, this decline is poorly understood. Here, we provide spatial evidence that cumulative stress interactions, particularly mechanical damage, contribute to Taxus mortality.