Geoscience Reference
In-Depth Information
2.0
A
B
Pacific Northwest
California
Interior
<1000 m
1000 to 2000 m
>2000 m
1.5
1.0
0.5
0.0
2.0
C
D
E
Abies
Pinus
Tsuga
Other
<25 yr
25-250 yr
>250 yr
<15 cm
15 to 40 cm
>40 cm
1.5
1.0
0.5
0.0
1960 1970
1980
1990
2000
1960
1970
1980
1990
2000
1960
1970
1980
1990
2000
Year
FIGURE 8.2 Modeled.trends.in.tree.mortality.rates.for.(A).regions,.(B).elevational.class,.
(C). stem. diameter. class,. (D). genus,. and. (E). historical. ire. return. interval. class.. (From. van.
Mantgem,. P.J.,. N.L.. Stephenson,. J.C.. Byrne,. L.D.. Daniels,. J.F.. Franklin,. P.Z.. Fulé,. M.E..
Harmon,.J.M..Smith,.A.H..Taylor,.and.T.T..Veblen..2009..Widespread.increase.of.tree.mortal-
ity.rates.in.the.western.United.States.. Science .323:521-24.)
Warming-induced. tree. mortality. is. consistent. with. both. the. apparent. role. of.
warming.in.episodes.of.recent.forest.die-back.in.western.North.America.(Breshears.
et.al..2005;.Raffa.et.al..2008;.Adams.et.al..2009).and.the.positive.correlation.between.
short-term.luctuations.in.background.tree.mortality.and.water.deicits.reported.in.
California.and.Colorado.(Bigler.et.al..2007;.van.Mantgem.and.Stephenson.2007)..
Over.time,.an.increase.in.background.tree.mortality.rates.could.lead.to.altered.for-
est. structure,. habitat. quality,. ire. hazard,. and. carbon. storage.. Perhaps. even. more.
important,.in.some.cases.these.chronic.increases.in.mortality.could.be.symptomatic.
of.forests.that.are.stressed.and.vulnerable.to.abrupt.die-off.
WMI. is. making. signiicant. contributions. to. regional. and. global. syntheses. of.
climate-induced.forest.mortality.through.the.Cordillera.Forest.Dynamics.Network.
(CORFOR,.North.and.South.American.mountains;.http://mri.scnatweb.ch/networks/
mri-amercian-cordillera/-cordillera-forest-dynamics-networkcorfor.html).. In. 2007,.
WMI.convened.an.international.workshop.on.climate-induced.forest.dieback,.lead-
ing.to.subsequent.synthesis.publications.(Allen.2009;.Allen.et.al..2010)..Recent.and.
ongoing. WMI. research. continues. to. address. key. uncertainties. in. forest. mortality.
processes.(McDowell.et.al..2008;.Breshears.et.al..2009;.McDowell.et.al..2010).
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