[MCN] Darcy's law: Forests and the sustainability question

[Lance Olsen]

"Drought and heat-induced tree mortality is accelerating in many 
forest biomes as a consequence of a warming climate, resulting in a 
threat to global forests unlike any in recorded history (1-12). 
Forests store the majority of terrestrial carbon, thus their loss may 
have significant and sustained impacts on the global carbon cycle 
(11,12). We use a hydraulic corollary to Darcy's law, a core 
principle of vascular plant physiology (13), to predict 
characteristics of plants that will survive and die during drought 
under warmer future climates. Plants that are tall with isohydric 
stomatal regulation, low hydraulic conductance, and high leaf area 
are most likely to die from future drought stress. Thus, tall trees 
of old-growth forests are at the greatest risk of loss, which has 
ominous implications for terrestrial carbon storage. This application 
of Darcy's law indicates today's forests generally should be replaced 
by shorter and more xeric plants, owing to future warmer droughts and 
associated wildfires and pest attacks. The Darcy's corollary also 
provides a simple, robust framework for informing forest management 
interventions needed to promote the survival of current forests. 
Given the robustness of Darcy's law for predictions of vascular plant 
function, we conclude with high certainty that today's forests are 
going to be subject to continued increases in mortality rates that 
will result in substantial reorganization of their structure and 
carbon storage."

Bold emphasis added

Nathan G. McDowell and Craig Allen. Darcy's law predicts widespread 
forest mortality under climate warming. Nature Climate Change 
Published Online: 18 MAY 2015
DOI: 10.1038/NCLIMATE2641
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"Although it is encouraging to know that Douglas-fir forests will 
acclimate to a warmer climate, in some regions, this increased 
drought tolerance may come at the expense of a relatively fast growth 
rate that is prized by land managers. 'We found that populations 
could have good growth and reasonable drought resistance, or 
reasonable growth and good drought resistance. You can't have both 
maximum growth and maximum drought resistance,' Bansal explains."

http://www.fs.fed.us/pnw/sciencef/scifi179.pdf

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"I KEEP six honest serving-men
  (They taught me all I knew);
Their names are What and Why and When
  And How and Where and Who."

Rudyard Kipling

Briefly discussed here:
http://schoolofthinking.org/2008/08/kiplings-six-honest-men/

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