Kristen(Welsh(Unwala( Pathfinder(Fellowship(Final(Report( Partitioning)sources)of)water)vapor)flux)to)the)atmosphere)from)subalpine)forest) during)spring)snowmelt) Abstract( Partitioning(evapotranspiration((ET)(sources(is(key(for(understanding(responses(of( terrestrial(ecosystems(and(water(budgets(to(disturbance.(Vegetation(heterogeneity,(in( addition(to(spatial(and(temporal(variations(of(source(contributions,(makes(prediction( and(modeling(of(these(components(complicated.(Fine(scale(isotope((δ18O(and(δD)( measurements(of(sources(compared(with(water(vapor(isotope(composition(can(provide( a(greater(understanding(of(the(potential(temporal(shifts(of(ET(sources.(To(better( understand(how(ET(sources(change(during(spring(snowmelt,(we(analyzed(stable(isotope( composition(of(water(vapor(concurrently(with(terrestrial(water(sources(in(a(subalpine( forest.(This(work(was(conducted(during(the(course(of(six(weeks(at(the(Glacier(Lakes( Ecosystem(Experiment(Site(in(Wyoming.( Objectives( The(main(objective(of(this(research(project(was(to(better(understand(how(ET(sources( shift(temporally(during(spring(snowmelt(in(a(subalpine(forest.(To(address(this(objective,( we(examined(the(stable(isotope(composition((δ18O(and(δD)(of(water(vapor(at(the( vegetation(surface(and(of(terrestrial(water(sources((snow,(surface(water,(plants,(and( soil)(to(characterize(fluxes(as(snowmelt(progressed(and(plant(activity(increased.(( Travel(and(Work(Completed( Between(May(and(June(2014,(I(relocated(to(the(University(of(Wyoming((UW)(from(the( University(of(Idaho(to(conduct(this(research(project(with(David(Williams.(This(work(was( conducted(in(a(subalpine(watershed(located(in(southeastern(Wyoming(during(a(sixXweek( period(in(the(early(growing(season.(During(my(time(in(Laramie,(I(made(weekly(trips(to( our(field(site(at(the(Glacier(Lakes(Ecosystem(Experiments(Site((GLEES)(in(the(Medicine( Bow(National(Forest.(We(measured(the(stable(isotope(composition(of(δ18O(and(δD(in( water(vapor(at(the(vegetation(surface(using(an(isotope(laser(spectrometer.(Fieldwork( consisted(of(collecting(samples(for(the(main(sources(of(water(vapor(in(the(system,( including(snow,(surface(water,(soil,(tree(cores,(and(leaves.(These(samples(were( transported(to(UW’s(Stable(Isotope(Facility((SIF),(where(I(spent(additional(time( preparing(samples(and(performing(water(extractions(on(soil(and(plant(matter.( Terrestrial(samples(are(being(analyzed(via(a(highXtemperature(conversion(elemental( analyzer(coupled(with(an(isotope(ratio(mass(spectrometer((TC/EAXIRMS),(in(addition(to(a( wavelengthXscanned(cavity(ringXdown(spectroscopy(system((Picarro,(Inc.).(These(
samples(have(been(submitted(for(analyses,(and(we(will(be(receiving(results(within(the( next(several(weeks.( Preliminary(Results(and(Planned(Future(Work( At(the(time(of(this(report,(only(half(of(the(snow(samples(have(been(processed(for( analysis,(and(we(are(still(waiting(analyses(for(the(soils(and(plant(matter(and(results(from( the(isotope(laser(spectrometer((for(water(vapor).(Therefore,(we(are(unable(to(draw( preliminary(conclusions(at(this(time.(Snow(samples(from(the(first(three(weeks(of( sampling(have(been(analyzed(and(reveal(a(Local(Meteoric(Water(Line((LWML)(of(δD(=( 6.7(*(δ18O(–(16.2((note(that(the(Global(Meteoric(Water(Line(is(δD(=(8(*(δ18O(–(10).( Examining(the(LMWL(for(each(week’s(samples,(we(see(a(slight(decrease(in(the(slope(and( intercept(of(the(line(as(snowmelt(progresses.(However,(without(receiving(the(remaining( results,(we(cannot(draw(any(conclusions(at(this(time.( We(will(collaborate(over(the(next(few(months(to(discuss(results,(analyze(data,(and(begin( preparing(a(summary(of(findings.(I(plan(to(present(results(from(this(research(at(the(Fall( Meeting(for(the(American(Geophysical(Union(in(December(2014.(Additionally,(we(plan( on(publishing(a(manuscript(with(the(results(of(this(study(in(early(2015.(( Summary(Statement( I(feel(that(the(Pathfinder(Fellowship(was(one(of(the(most(positive(experiences(of(my( Ph.D.(Expanding(my(isotope(knowledge(and(professional(network(was(extremely( beneficial(to(my(career(goals.(This(project(provided(me(with(a(unique(opportunity(to( work(at(a(different(university(with(faculty(outside(of(my(specific(discipline.(My(personal( research(objectives(for(this(project(were(to(1)(conduct(relevant(research(in(a(different( ecosystem(from(my(dissertation(research,(2)(learn(methodology(for(collecting(and( analyzing(isotopic(samples(for(plants(and(snow,(and(3)(strengthen(my(understanding(of( evapotranspiration((ET)(processes(and(ecohydrology(to(improve(my(work(as(a( hydrologist.(Having(the(opportunity(to(travel(to(Wyoming(through(the(Fellowship( enabled(me(to(conduct(research(in(a(different(ecosystem(from(Costa(Rica((where(my( dissertation(research(was(conducted),(and(I(learned(a(significant(amount(from(this( experience.(I(learned(new(methodology(regarding(the(collection(of(plant(and(snow( samples,(and(I(also(had(the(opportunity(to(learn(how(to(conduct(plant(water(extractions( from(collected(samples(in(the(lab.(This(work(has(piqued(my(interest(in(ecohydrology( research(and(will(strengthen(my(work(as(an(isotope(hydrologist(in(the(future.(I(look( forward(to(further(collaborations(with(David(Williams(and(others(at(the(University(of( Wyoming(in(coming(months.( ! ) )
Appendix:)Photos))
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Figure'1:'A'view'of'the'Eddy4Covariance'tower'located'at'the'Glacier'Lakes'Ecosystem'Experiments'Site.' We'measured'stable'isotope'composition'of'water'vapor'with'an'isotope'laser'spectrometer'mounted'on' the'tower.)
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Figure'2:'A'view'of'the'study'site,'where'we'measured'terrestrial'sources'of'water'vapor'in'trees,'snow,' surface'water,'and'soil.)
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Figure'3:'Kristen'Welsh'uses'a'snow'core'to'collect'samples'of'snow'to'measure'stable'isotope' composition.)
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Figure'4:'Kristen'Welsh'collects'a'tree'core'to'measure'stable'isotope'composition'of'plant'water.)
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