Massive Forest Dieback SW US

Summary: • Tree death is an important ecological process, but we don’t know very much about it. • MFD (Massive Forest Dieback) is often driven by stress from extreme climate events, rather than equilibrial mean climate conditions. • MFD occurs naturally in many forest types. However, there are indications that emerging patterns of dieback in some montane areas are being amplified by global climate change, and predictions of more extreme climate events suggest risk of increases in associated forest dieback episodes. • We cannot accurately predict the effects of climate change on montane forest ecosystems without better field data and model incorporation of species-specific thresholds of stress-induced tree mortality, and the dynamics of amplifying disturbances like insect outbreaks and fire. • CIRMOUNT could help address these knowledge gaps by fostering regional networks for long-term monitoring and research on: 1) plot-based demographies of multiple tree species across landscape and regional gradients to get data on pulses of mortality and natality; 2) tree growth using straightforward dendrometer band methods; 3) feedbacks between forest dieback, other disturbances, and overall ecosystem patterns and processes; and 4) effectiveness of mitigation strategies (e.g., thinning, prescribed burning).