Geoscience Reference
In-Depth Information
Of.particular.concern.Westwide.are.increases.in.ire.area.in.a.warming.climate.
and. the. effects. of. extreme. wildire. events. on. ecosystems. (Gedalof. et. al.. 2005;.
Lutz. 2008;. Littell. et. al.. 2009).. For. example,. in. 2006,. the. Tripod. Complex. Fire.
in. north-central. Washington. burned. over. 80,000. ha,. much. of. it. higher. severity.
than.expected.from.historical.ires..WMI.researchers.have.documented.strong.cli-
matic.controls.on.area.burned.by.wildire.across.the.West.at.the.spatial.scales.of.
entire.states.(McKenzie.et.al..2004),.ecoprovinces.(Littell.et.al..2009),.and.sections.
within.ecoprovinces.(Littell.et.al..2010)..In.forests.across.the.Northwest,.climate.
during.the.ire.season.appears.to.control.area.burned,.whereas.in.arid.mountains.
and. shrublands,. antecedent. climate. (e.g.,. wetter. and. cooler. summers. or. winters.
preceding. the. ire. season). can. increase. area. burned. during. the. ire. season. by.
increasing.fuel.abundance.and.continuity.(Littell.et.al..2009)..WMI.research.has.
also. synthesized. sediment. yields. after. wildland. ire. in. different. rainfall. regimes.
across.the.western.United.States.(Moody.and.Martin.2008),.providing.key.context.
for.potential.climate-mediated.watershed.changes.in.post-ire.runoff.and.erosion.
relationships.
MPB.infestations.have.historically.occurred.frequently.and.extensively.through-
out. the. American. West. (Logan. and. Powell. 2001).. Warming. and. drought. affect.
development.rates.of.beetle.life.stages,.winter.mortality,.and.host-tree.susceptibility.
(Logan.and.Powell.2001;.Carroll.et.al..2004;.Oneil.2006)..WMI.has.examined.MPB.
outbreaks.Westwide,.with.focused.studies.on.outbreak.potential.within.Washington.
State..Across.the.West,.stand.structural.conditions.make.host.species.susceptible.to.
beetle.attack.(Oneil.2006;.Hicke.and.Jenkins.2008),.but.we.expect.host.vulnerability.
to.become.increasingly.linked.to.drought.stress.as.warming.continues.(DeLucia.et.
al..2000;.Oneil.2006)..MPB.outbreaks.are.facilitated.when.the.insect's.reproductive.
cycle.is.very.close.to.one.year,.such.that.larvae.emerge.at.an.optimal.time.for.feed-
ing.and.dispersal.(Logan.and.Powell.2001)..As.temperatures.increase,.the.life.cycle.
shortens;.therefore,.future.climatic.change.is.predicted.to.reduce.the.area.of.climatic.
suitability.for.the.MPB.at.low.elevations,.but.increase.suitability.at.higher.elevations.
(Hicke. et. al.. 2006;. Littell. et. al.. 2010).. WMI. contributed. signiicantly. to. a. recent.
synthesis.of.the.causes.and.ecological.consequences.of.MPB.outbreaks.in.western.
North.America.(Bentz.et.al..2009).
Although.their.nature,.timing,.and.effects.are.only.beginning.to.be.understood,.
synergistic. interactions. between. disturbances. are. producing. larger. effects. than.
would. occur. from. either. disturbance. independently.. For. example,. MPB. outbreaks.
have.been.linked.to.the.increased.likelihood.of.stand-replacing.ire.and.changes.in.
ire.behavior,.with.the.nature.of.the.effect.depending.on.the.time.since.infestation.
(Lynch. et. al.. 2006;. Jenkins. et. al.. 2008),. although. there. is. conlicting. evidence. to.
support.the.idea.of.elevated.ire.hazard.following.bark.beetle.outbreaks.(Romme.et.
al..2006;.Kulakowski.and.Veblen.2007;.Bentz.et.al..2009)..Combined.with.increas-
ing.climatic.stress.on.tree.populations.and.growth,.disturbance.interactions.can.alter.
forest.structure.and.function.faster.than.could.be.expected.from.species.redistribu-
tion.or.disturbance.alone..Simultaneous.climatically.driven.shifts.in.the.locations.of.
species'.optima,.ecosystem.productivity,.disturbance.regimes,.and.the.interactions.
between.them.could.reset.forest.succession.over.large.areas.and.short.time.frames.
