[MCN] "Massive conifer mortality due to" rising temperature

[Lance Olsen]

Nature Climate Change (2015) doi:10.1038/nclimate2873
Published online 21 December 2015

Multi-scale predictions of massive conifer mortality due to chronic 
temperature rise
N. G. McDowell, A. P. Williams, C. Xu, W. T. Pockman, L. T. Dickman, 
S. Sevanto, R. Pangle, J. Limousin, J. Plaut, D. S. Mackay, J. Ogee, 
J. C. Domec, C. D. Allen, R. A. Fisher, X. Jiang, J. D. Muss, D. D. 
Breshears, S. A. Rauscher & C. Koven

Abstract (Bold emphasis added)
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2873.html

Global temperature rise and extremes accompanying drought threaten 
forests(1, 2) and their associated climatic feedbacks (3, 4). 
Our ability to accurately simulate drought-induced forest impacts 
remains highly uncertain (5, 6) in part owing to our failure to 
integrate physiological measurements, regional-scale models, and 
dynamic global vegetation models (DGVMs). Here we show consistent 
predictions of widespread mortality of needleleaf evergreen trees 
(NET) within Southwest USA by 2100 using state-of-the-art models 
evaluated against empirical data sets. Experimentally, dominant 
Southwest USA NET species died when they fell below predawn water 
potential thresholds (April-August mean) beyond which photosynthesis, 
hydraulic and stomatal conductance, and carbohydrate availability 
approached zero. The evaluated regional models accurately predicted 
NET pd, and 91% of predictions (10 out of 11) exceeded mortality 
thresholds within the twenty-first century due to temperature rise. 
The independent DGVMs predicted 50% loss of Northern Hemisphere NET 
by 2100, consistent with the NET findings for Southwest USA. Notably, 
the global models underestimated future mortality within Southwest 
USA, highlighting that predictions of future mortality within global 
models may be underestimates. Taken together, the validated regional 
predictions and the global simulations predict widespread conifer 
loss in coming decades under projected global warming.

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"He who knows he has enough is rich."
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