Geoscience Reference
In-Depth Information
long-term. responses. of. key. ecosystem. parameters. (herbaceous. cover,. runoff,. ero-
sion,.tree.growth,.arthropod.populations).to.interannual.and.decadal.climatic.varia-
tion.. Documentation. of. forest. die-off. following. extended. drought. has. shown. that.
drought.and.heat.can.exceed.critical.thresholds.of.tree.mortality.at.the.regional.scale..
Reconstructed.crown.ire.dates.from.12.of.the.largest.aspen.stands.in.the.southern.
Rockies. reveal. correlations. with. past. droughts. and. region-wide. surface. ire. years..
Sediment.cores.contain.charcoal.deposits.that.record.evidence.of.ires.throughout.the.
Holocene.and.suggest.that.the.post-1900.cessation.of.widespread.ire.in.the.southern.
Rockies.is.anomalous.on.millennial.time.scales..Ecohydrologic.research.is.reveal-
ing.the.critical.importance.of.climate-sensitive.land.surface.cover.characteristics.in.
controlling.patterns.and.rates.of.soil.erosion.in.semiarid.landscapes.
COLLABORATIVE APPROACH
WMI.builds.on.past.research.in.each.of.the.ive.bioregions..The.depth.and.breadth.
of. place-based. knowledge. represented. by. this. work. strengthens. multisite. regional.
comparisons..WMI.employs.cross-site.syntheses.of.long-term.data,.modeling,.and.
workshops.to.convene.subject-matter.experts.from.a.variety.of.scientiic.disciplines..
Mechanistic.understanding.of.how.climatic.variability.and.change.affect.ecosystems.
directly.(e.g.,.by.affecting.productivity).and.indirectly.(as.mediated.through.distur-
bance). has. been. explored. primarily. through. natural. experiments. in. time,. natural.
experiments.in.space,.and.synthetic.modeling.
WMI. conducts.
natural experiments in time
. through. a. variety. of. paleoecologi-
cal. data. and. contemporary. information. sources.. At. millennial. time. scales,. pol-
len. and. charcoal. in. sediments. reveal. ecosystem. responses. to. long-term. climatic.
shifts. (Whitlock. and. Anderson. 2003).. At. decadal. to. millennial. time. scales,. tree.
rings.reveal.annual.to.seasonal.changes.in.climatic.and.ire.regimes.(Swetnam.and.
Baisan. 2003),. and. broad. demographic. trends. in. forests. (Veblen. and. Lorenz. 1991;.
Swetnam.and.Betancourt.1998)..At.time.scales.of.a.few.years.to.a.century,.instru-
mental.records,.written.records,.photographs,.and.plot.data.offer.ine.resolution.for.
mechanistic.understanding..Quasi-periodic.climatic.phenomena.such.as.the.Paciic.
Decadal.Oscillation.(Mantua.et.al..1997).and.El.Nĩo-Southern.Oscillation.(Diaz.
and.Markgraf.2000).offer.a.context.for.climatic.change,.particularly.when.they.drive.
climatic.extremes.
WMI.conducts.
natural experiments in space
by.a.subcontinental.network.of.ield.
sites. in. aquatic. and. terrestrial. systems.. This. allows. WMI. to. seek. generalizations.
across. temperature. regimes. (continental. vs.. maritime. [longitudinal. comparisons],.
warm. vs.. cool. [latitudinal. comparisons]). and. precipitation. regimes. (e.g.,. mediter-
ranean. vs.. monsoonal. [Sierra. Nevada. vs.. southern. Rockies],. wet. vs.. dry. [Paciic.
Northwest.to.southern.Rockies])..At.regional.scales,.steep.elevational.gradients.that.
exist. within. each. WMI. region. are. paralleled. by. steep. temperature. and. moisture.
gradients.
WMI.conducts.modeling.studies.to.understand.ecosystem.function.and.effects.
of. climatic. warming.. We. primarily. use. RHESSys. (Regional. Hydro-Ecological.
Simulation. System). (Baron. et. al.. 2000a;. Christensen. et. al.. 2008). as. a. frame-
work.to.assess.effects.on.aquatic.and.terrestrial.systems..RHESSys.allows.us.to.
