Geoscience Reference
In-Depth Information
disturbance..The.coniguration.of.the.network.as.a.series.of.permanent.research.sites.
allows.for.observation.of.both.the.spatial.and.temporal.patterns.of.these.ecosystem.
properties..Clearly,.climate.(as.previously.deined).is.a.major.control.over.several.of.
these.core.ecological.variables,.especially.net.primary.productivity..For.this.reason,.
climate.observations.have.been.among.the.fundamental.data.sets.collected.at.each.
LTER.site.since.the.inception.of.the.program.
There. have. been. a. number. of. research. projects. aimed. at. relating. climate. and.
ecological.response.within.LTER,.including.the.Climate.Variability.and.Ecosystem.
Response. (CVER). project,. a. comprehensive,. network-wide,. cross-site. program.
(Greenland. et. al.. 2003).. The. CVER. program. was. organized. into. a. framework. of.
time.scales..Within.the.CVER.project,.investigations. between.climate.drivers.and.
various. ecological. responses. were. conducted. at. a. number. of. LTER. sites,. at. tem-
poral. scales. ranging. from. less. than. a. year. to. centuries/millennia. (using. modeling.
approaches.and.proxy.measures)..At.each.of.these.temporal.scales,.it.was.found.that.
the. ecosystems. responded. to. climatic. events. or. episodes. that. exceeded. a. certain.
threshold. and. that. ecosystems. to. a. certain. extent. seemed. to. buffer. the. effects. of.
climatic.variability.(Greenland.and.Kittel.2002)..The.studies.also.found.that.at.many.
LTER.sites,.ecosystem.responses.were.related.to.a.number.of.well-known.climate/
circulation. patterns,. including. the. El. Nĩo/Southern. Oscillation. (ENSO),. North.
Atlantic.Oscillation.(NAO),.Paciic.North.American.pressure.cycle.(PNA),.and.the.
Paciic.Decadal.Oscillation.(PDO)..Linking.site-based.ecosystem.response.variables.
to.global.circulation.modes.is.signiicant,.because.it.shows.how.large-scale.climate.
events.“connect”.with.localized.responses..The.results.of.these.studies.also.clearly.
demonstrated.the.importance.of.long-term,.site-based.science.for.understanding.and.
monitoring.the.linkages.between.climate.and.ecosystem.response.
Although.the.CVER.program.provided.information.and.comparative.analysis.of.
the.LTER.sites,.it.did.not.consider.sites.within.their.regional.context..Hence,.a.ques-
tion.arises:.How.well.do.LTER.sites.represent.the.region.in.which.they.are.located?.
The.question.is.important,.because.an.explicit.goal.of.climate/environment.research.
at.sites.such.as.those.that.comprise.the.LTER.network.is.to.understand.how.the.biotic.
component.of.a.particular.ecosystem.may.respond.to.its.environment..Because.the.
type. of. intensive. ecosystem. monitoring. done. at. individual. sites. is. not. practical. at.
the.biome.scale,.it.becomes.necessary.to.extrapolate.based.on.site-speciic.results..
In.order.for.these.site-speciic.results.to.be.valid.representations,.the.site.itself.must.
represent.its.region.well..From.a.climatic.perspective,.this.problem.is.complicated.
by.two.problems.arising.from.the.concept.of.a.region..First,.climate.regions.often.
do.not.coincide.exactly.with.ecoregions..Second,.climatic.regionalizations.are.typi-
cally.based.on.measurable.climatic.state.variables.(i.e.,.temperature,.precipitation).
and.not.on.the.dynamic.processes.that.shape.the.climate.of.a.region..Clearly,.a.bet-
ter.understanding.of.how.these.dynamic.processes.couple.to.the.ecological.system.
would.enable.ecologists.to.better.understand.how.an.ecosystem.is.linked.to.the.larger.
global.system..In.this.chapter,.I.explore.this.idea.by.(1).using.correlation.and.multi-
variate.analysis.to.link.a.climatic.state.variable.(precipitation).to.several.modes.of.
global.circulation,.in.order.to.establish.a.geographic.pattern.of.these.linkages;.and.
(2).determine.how.well.a.selected.subset.of.LTER.sites.“represent”.the.circulation.
region.in.which.they.are.located.
