Droughts legacy: Hydraulic deterioration underlies widespread aspen forest die-off and portends increased future risk

Background/Question/Methods

Forests take up nearly a quarter of human carbon emissions annually and store large amounts of carbon.  Yet recent drought-induced, widespread forest die-offs highlight that climate change could threaten these carbon sinks. We lack a fundamental understanding, however, of how trees die during drought especially within a multi-year framework. This knowledge gap hinders mechanistic modeling and prediction of forest die-off. Here, we examine the physiological basis of a recent widespread die-off of trembling aspen (Populus tremuloides) across much of western North America. We investigate how hydraulic stresses accumulate and are repaired over seasons and years.

Results/Conclusions

Hydraulic deterioration accumulated over multiple years and successfully predicted the probability of inter-year stem mortality. Surviving regions of these forests may be more vulnerable to future droughts due to this accumulated hydraulic damage. Thus, the accumulation of stress and repair of stress-induced damage may be critical for avoiding plant mortality with implications for coupled climate-vegetation models.