Geoscience Reference
In-Depth Information
INTRODUCTION
Mountains. in. western. North. America. are. beginning. to. see. changes. in. ecosystem.
processes. primarily. from. climate-forced. changes. in. water. dynamics.. With. earlier.
snowmelt.and.increasing.proportions.of.rain.versus.snow.(Mote.2003;.Stewart.et.al..
2005;.Knowles.et.al..2006),.drought.stress.is.increasing..Cascading.effects.include.
increasing.vegetation.mortality.(van.Mantgem.et.al..2009),.dieback.of.entire.forest.
stands.(Allen.and.Breshears.1998;.Breshears.et.al..2005),.longer.and.more.intense.
ire.seasons.(McKenzie.et.al..2004;.Westerling.et.al..2006;.Littell.et.al..2009a),.and.
increased.susceptibility.to.insects.and.pathogens.(Carroll.et.al..2004;.Breshears.et.
al..2005;.Hicke.et.al..2007)..Model.projections.(Littell.et.al..2009).suggest.that.all.
these.phenomena.will.become.even.more.pronounced.in.coming.years.(IPCC.2008;.
Milly.et.al..2008).
Climate-forced.changes.in.hydrology.at.high.elevations.are.being.caused.by.tem-
perature-driven. changes. in. winter. precipitation. form. and. snowmelt. and. by. direct.
summer.warming.(Redmond.2007;.Baron.et.al..2009)..Permanent.snow.and.glaciers.
are.retreating.rapidly.(Hall.and.Fagre.2003;.Granshaw.and.Fountain.2006;.Hoffman.
et.al..2007),.portending.the.loss.of.smaller.glaciers.in.the.continental.United.States.
within.the.century.(Dyurgerov.and.Meier.2000),.and.water.chemistry.is.changing.
as.weathering.rates.increase.and.new.sediments.are.exposed.(Lafreniere.and.Sharp.
2005;.Williams.et.al..2007b;.Thies.et.al..2007;.Baron.et.al..2009)..Increased.stream.
temperature.and.decreased.summer.low.will.strongly.affect.mountain.aquatic.eco-
systems.(Hauer.et.al..1997;.Ficke.et.al..2007).
These. ongoing. and. projected. changes. in. western. mountains. are. important. for.
both. people. and. ecosystems. in. the. western. United. States.. Western. mountains. are.
the. water. source. for. agriculture. and. 60. million. people,. provide. timber. and. other.
commodities,. and. support. recreation.. National. parks. and. national. forests. are. res-
ervoirs.of.reasonably.intact.natural.ecosystems.that.protect.critical.wildlife.habitat.
and.maintain.natural.ecological.processes..The.Western.Mountain.Initiative.(WMI).
has. developed. a. collaborative,. multidisciplinary. research. program. to. address. how.
climatic. variability. and. change. inluence. forest. processes,. disturbance. dynamics,.
mountain.hydrologic.changes,.and.ecohydrologic.interactions.among.climate,.water,.
and. vegetation.. Long-term. studies. by. WMI. have. identiied. regional. responses. in.
hydrology,.disturbance.patterns,.and.vegetation.dynamics.caused.by.a.combination.
of. regional. climatic. patterns. (van. Mantgem. and. Stephenson. 2007;. Groisman. and.
Knight.2008;.Littell.et.al..2009,.2010),.topographic.complexity.(Hicke.et.al..2006;.
Christensen.et.al..2008),.and.landscape.controls.(Tague.et.al..2008).
The.WMI.research.program.has.addressed.four.research.questions.for.Western.
mountains:
.
1.. How.are.climatic.variability.and.change.likely.to.affect.disturbance.regimes.
(particularly.ire)?
.
2.. How.are.changing.climate.and.disturbance.regimes.likely.to.affect.the.com-
position,.structure,.and.productivity.of.vegetation.(particularly.forests)?
.
3.. How.will.climatic.variability.and.change.affect.hydrologic.processes.in.the.
mountainous.West?
