The influences of climate on aspen dieback

Understanding the links between climatic variability and tree mortality is an important goal of current ecological research, but this relationship remains poorly understood for some widespread species such as quaking aspen (Populus tremuloides Michx.). Recent observations indicate a sudden onset and rapid progression of quaking aspen dieback in the western United States, which may be climatically driven. We used dendroecological methods to test how climatic variability influences aspen grown and mortality in northwestern Colorado and southern Wyoming. Recent growth and mortality of quaking aspen is strongly associated with climatic variation in this region. In stands undergoing recent aspen dieback (1) the growth of aspen was inhibited by warm temperatures, except at the highest elevations (2) the growth of aspen that died was more sensitive to temperature variation prior to mortality than the growth of living aspen, (3) mortality of aspen was preceded by multiple years of reduced growth, and (4) the frequency of mortality was associated with multiple years of drought as indicated by negative PDSI values. The results of this study suggest that the recent widespread mortality of aspen is strongly associated with recent climatic conditions.

► We test how climate influences aspen growth in stands experiencing aspen decline.
► Growth of aspen was inhibited by warm temperatures.
► Growth of aspen that died varied more with temperature than growth of living aspen.
► Mortality of aspen was preceded by multiple years of reduced growth.
► Mortality frequency was associated with multiple years of negative PDSI values.