Flashy, decoupled, or declining? Single theories each fail to explain the diversity of drought mortality signals in tree rings

Résumé fourni par la source

Increasing drought frequency and severity are driving global forest dieback. Growth recorded in tree rings may predict drought ‘winners’ and ‘losers,’ but past studies of growth in drought-killed trees have produced conflicting support for different theories about drought mortality. We found that clusters of growth behaviors computed from the rings of 2,934 drought-killed and drought-surviving trees from seven species were not consistent with any single theory. Drought-killed subalpine fir and Engelmann spruce trees exhibited “flashy” growthhighly variable climate-growth responses over timecompared to survivors. Drought-killed Scots pine and Norway ospruce trees showed stable, climate-insensitive growth compared to survivors, suggesting “decoupling” from climate. Finally, in red oak and subalpine fir, disturbances like fire, logging, and biotic agents possibly influenced declines in climate sensitivity in both drought-killed and surviving trees. Our consolidated conceptual framework may be useful for predicting future tree mortality, while providing enhanced ecological and physiological understanding.

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