Historic declines in growth portend trembling aspen death during a contemporary leaf miner outbreak in Alaska

Climate change-driven droughts and insect outbreaks are becoming more frequent widespread, increasing forest vulnerability to mortality. By addressing the impacts of climate insects on tree growth preceding death, we can better understand mortality risk under a changing climate. Here, used stature interannual (basal area increment; BAI) assess processes leading trembling aspen (Populus tremuloides) survival or during an unprecedented leaf miner (Phyllocnistis populiella) outbreak in boreal North America. We identified eight sites (22 plots) longest running monitoring network Alaska, spanning ~350 km latitude, that experienced ≥0.25 Mg·ha−1·yr−1 outbreak. compared size canopy position, patterns, sensitivity mining survived (living; n = 84) vs. died (dying; 76) linked normalized difference vegetation index (NDVI) plot-level stand biomass recruitment, growth, Dying were subcanopy, smaller diameter, after drought 1957 had lower than living until death. Before outbreak, all trees was positively influenced by moisture negatively temperature, but only maintained this response Leaf reduced both groups, exerting at least twofold greater impact The NDVI captured mortality, yet it nearly two times strongly associated with dying 12 These differences suggest may inadequately detect insect-driven dieback dispersed across biome. Our findings reveal historic triggered multi-decadal decline predisposed while is affected P. populiella. conclude as warms increase frequency magnitude high latitudes, should expect see persistent declines increases