白頭鶴種群與雁群在越冬過程中的生境利用和資源分割

白頭鶴種群與雁群在越冬過程中的生境利用和資源分割

通過碳源反應(yīng)來創(chuàng)造國內(nèi)碳源這片區(qū)域是midle，是低增量飛機的表面。在新的一年里，土地恢復(fù)和灌溉。Speciescoexistthroughresourcepartitioning,includingthepartitionofhabitat,foodandhabitatutilizationtime(Schoener,1974;Mittelach,1984;Reinert,1984).Variationsofhabitatutilizationandforagingbehaviorofcoexistingspecieshavebeenconsideredevolutionarystrategiestopartitionlimitedresourcesandtominimizepotentialinterspecificcompetition(Jenni,1969;Willard,1977;Ishtiaq,2010).Temporal-spatialvariationsofhabitatsarethemainfactorsaffectinghabitatutilization(Kellyetal.,1996;Ribeiro,2004).Inahighlydegradedwetlandecosystem,commonresourcesaresharedbylargeflocksofmigratorywaterbirds.Thesehigh-densitywaterbirdflocksmayinducegreaterinterspecificcompetition(Burgeretal.,1977;Alataloetal.,1985;Beerensetal.,2011).Asaresult,significantdifferencesmaybefoundinmicrohabitatutilizationandfoodselection(DavisandSmith,2001;Vahletal.,2005;KoberandBairlein,2009).CranesandgeesearecommonwinteringwaterbirdsinhabitingthelakesofthemiddleandlowerYangtzeRiverfloodplain.TheHoodedCrane(Grusmonacha)isavulnerablespecies(VU)ontheIUCNredlistandaspeciesofwildlifeunderfirstclassstateprotectioninChina.TheBeanGoose(Anserfabalis),theGreaterWhite-frontedGoose(A.albifrons)andtheLesserWhite-frontedGoose(A.erythropus)arethreecommongoosespeciesinthewetlandsofthemiddleandlowerYangtzeRiverfloodplain.Theyareregardedasindicatorspeciesoflakeecosystemsduetotheirsensitivitytohabitatchange.ThesewaterbirdsmigratesouthwardstothewinteringgroundsinthemiddleandlowerreachesoftheYangtzeRiverinlateOctobereveryyear.ThemainhabitatofHoodedCranesandthesethreegoosespeciesinwinterarethegrasslands,farmlandsandshallow-waterareas.Ingeneral,thewinteringHoodedCranesoccupythedrylakeshores,grasslandsandpaddyfields.TheymainlyfeedontubersofVallisnerianatans,aswellasonseedlingsofPolygonumlapathifolium,occasionallyonPotamogetonmalainus,Phalarisarundinacea,Cynodomdactylon,Carexunisexualis,Cyperussp.,aswellasonwheatseedlings,ricegrains,spiralshellsandmussels.Theirdietisaffectedbytheavailabilityoffoodresourcesintheirwinteringhabitat(WangandHu,1986;Liuetal.,2001).Thethreegoosespeciesoftenassembleinmixedflocks,asaguildwithextremelysimilarcharacteristicsofhabitatutilization(Yang,2011;ChenandZhou,2011).SomeoftheirfoodresourcesoverlapwiththoseoftheHoodedCranes,suchasCarexspp.,Phalarisarundinacea,ricegrainsandCynodomdactylon(Foxetal.,2008;Zhaoetal.,2010).Hence,geesearethemajorcompetitorsofHoodedCranes.Thisstudyaims:(a)togainaninsightintothecharacteristicsofhabitatutilizationofwinteringHoodedCranesandthegooseguildinlakewetlandsand(b)toexploreresourcepartitioningbetweenHoodedCranesandthegooseguild.我u2004范圍ShengjinLake(116°55′–117°15′E,30°15′–30°30′N),locatedtothesouthoftheYangtzeRiverbank,isashallow-water,river-connectinglake.AriverisconnectedtothelakeviatheHuangpenSluicebuiltin1965.Thelakeareaisatitslargestat14000hainthehighwaterseason,whileitissmallestat3400hainthelowwaterseason.Thelakeusuallyisdividedintotwoparts:theupperpartandlowerpartfromsouthtonorth.Theregionwherethelakeislocatedbelongstothenorthernsubtropicalhumidzonewithanannualmeantemperatureof16.1°Candprecipitationof1600mm.ShengjinLakeisoneofthemostimportantwinteringandstopovergroundsalongtheYangtzeRiverforwaterbirds,especiallyHoodedCranes,BeanGeese,GreaterWhite-frontedGeeseandLesserWhite-frontedGeese.Asoneofthemajorwinteringgroundsformigratorywaterbirds,itwasapprovedin1986tobeestablishedasaprovincialnaturereserveandin1997itbecameanationalnaturereserve.ThepresentstudywascarriedoutintheupperpartofShengjinLake,whichislocatedinthesouthernpart,acoreareaofthisnaturereserve.Thelakebedissmoothandflat,whiletheterrainishighertowardsthesoutheast.CageaquacultureoperationshadbeenestablishedatShengjinLakeformorethantenyears,whilepondandenclosureculturearecommonlyseeninthelake.Inthelowwaterseason,thelakewaterretreatsandalargemudflatisexposedtoprovideaforaginghabitatfortheHoodedCraneandotherwinteringwaterbirds.Theforaginghabitats,consistingofwaterareas,mudflats,grasslandsandpaddyfields(Fig.1),showperiodicanddynamicchanges.u2004范圍latelateso能夠定義為u2005,關(guān)于lage-lahengeratchingpoldinglate/lage-lagesoratchingmotirats,lage-lacket3.3.ThehabitatutilizationofHoodedCranesandgeeseareaffectedbyperiodicchangesinthehydrologyandmudflatexposureofShengjinLake.Wedividedthewinteringperiodintothreestagesaccordingtothehydrologicalvariationsinthelake.TheearlystagewasbeforelateDecember.Duringthistimethelake,stillatahighwatertable,startedtorecede.ThemiddlestagewasfromtheearlyJanuarytolateFebruaryinthefollowingyear,whenthewaterleveldroppedquicklyandlargeareasofthelakeshorebecameexposed.ThelatestagewasfromlateFebruarytotheendofMarch,duringwhichthelakeshorehadbecomedryandthewaterlevelbegantoriseagain.ThehabitattypesoftheupperShengjinLakevariedwiththehydrologicalconditionsduringthelowwaterseason.Atthemiddlestage,habitatswereplentiful,includingdeep-waterareas,shallow-waterareas,mudflats,grasslandsandpaddyfields.Thedeep-waterareainthelakewasonly0.5mdeep.Theshallow-waterareareferstothewaterbodywithadepthoflessthan0.5m.Themudflatsaretidalflatswithlargeareasofthelakebeachexposed,whenthewaterhasretreated.Somesmartweeds,sedgesandotherplantsgrowinareaswherethewaterretreatsearly.Grasslandsaremudflatswithavegetationcoverofmorethan20%,dominatedbyherbaceousplants.Paddyfieldsareinpolderswherericeisplantedinthespringandsummerandharvestedinautumnandthenwheatisplantedinlatewinter.ForaginghabitatsforHoodedCranesandgeesearerelativelystableatacertainwinteringstageatShengjinLake(Caoetal.,2010;Zhouetal.,2010).TheseforaginghabitatsarecentralizedinXinjunvillage,aswellasintherangebetweenYang’etouandSheganvillages(Fig.1).相關(guān)程序設(shè)置WecombinedthemethodsoffixedrouteandfixedsiteobservationstoinvestigatethehabitatsattheupperpartofShengjinLakefromNovember15,2011toApril1,2012.Eachsurveycoveredthewholearrayofhabitattypes.Fourrouteswereincludedinonesamplingsurvey,whichlastedfrom1to3days.Samplingsurveyswhichwerenotcompletedwereexcludedfromthefinalsamples.Therefore,thesamplesizesofHoodedCraneandgeesewereequal.Thevaliddatacollectionconsistedofatotalof59daysand38samples,including15samplescollectedin30daysfortheearlywinteringstage,13samplescollectedin19daysforthemiddlewinteringstageand10samplesin10daysforthelatewinteringstage.ThedistributionofHoodedCranesandgeeseattheupperlakeweredeterminedbymeansofafixedroutesurvey.ThesurveyedrouteswerefromXinjuntoXiaoluzuivillage,XiaoluzuitoSheganvillage,XinjuntoShenshanzuivillageandfromShenshanzuitoSheganvillage.FixedsiteobservationewerecarriedoutwhenwefocusedonHoodedCranesand/orgeese.Theareawithinaradiusof1kmwasobservedbyabinoculartelescope(BOWAS8×42)andamonoculartelescope(SWAROVSKI20-60×80);werecordedthenumberandhabitattypes.Adirectcountingmethodwasemployedforsmallnumberofcranesandgeese(generallylessthan300birds).Forlargeflocks,agroupcountingmethodwasadopted.Thatis,theflockwasdividedintoseveralsmallerindividualgroupssuchas10,50to100.Thenumberofbirdsinthewholeflockwasestimatedbycountingthenumberofbirdsineachsmallerflock(HowesandBakewill,1989;Ma,2006).Sincethedietsofthethreegoosespeciesaresimilarandoftenmixedinhigh-densityflocks,thethreegoosespeciesweretreatedasoneguildforthepurposeofcounting.utilizationforad.BasedonthedistributionofthepopulationsofHoodedCranesandgeeseineachsurvey,theutilizationrates(U)ofallhabitattypesbyHoodedCraneorgooseguildwerecalculatedas:Ui=Ni/N,whereUiistheutilizationrateoftheithhabitattypebywaterbirds;NithenumberofthewaterbirdsintheithhabitattypeandNthetotalnumberofwaterbirdsinallhabitattypes.Themeanutilizationrate(Mean)andstandarderror(SE)inallhabitatsandallwinteringstageswerecalculated.TheutilizationratesofhabitatsbythewaterbirdsatthesamewinteringstagewerecomparedwithaKolmogorov-SmirnovtestinSPSS17.0.Theutilizationratesinfivehabitattypeswerecheckedtoseeiftheassumptionofanormaldistributionweremet.Ifmet(p>0.05),anindependent-samplettestwasperformed;ifnot(p<0.05),theMann-WhitneyUtestwasused.Thesignificancelevelwassetasα=0.05.TheShannon-Weinerdiversityindexwasusedtomeasurethewidthofthespatialniche(Krebs,1989;DavisandSmith,2001;KoberandBairlein,2009)oftheHoodedCraneandgooseguild.ThespatialnicheoverlapoftheHoodedCraneandthegooseguildwascalculatedusingPianka’s(1974)equation(Isacchetal.,2005;KoberandBairlein,2009).產(chǎn)品系統(tǒng)utilizedunthindrace.utilized治療.ThefourmajorhabitattypesforHoodedCranesatShengjinLakeconsistedofshallow-waterareas,mudflats,grasslandsandpaddyfields.Themostutilizedhabitattypewasgrasslandsattheearlywinteringstage,withautilizationrateof0.454±0.083(n=15),followedby0.427±0.088(n=15)forthepaddyfields.Theutilizationratesofshallow-waterareasandmudflatswererelativelylow,i.e.,0.053±0.024(n=15)and0.066±0.021(n=15),respectively.Themostfrequentlyutilizedhabitatsweregrasslandswithautilizationrateof0.435±0.115(n=13)andmudflatsof0.363±0.101(n=13)atthemiddlewinteringstage,followedby0.190±0.091(n=13)fortheshallow-waterareasand0.012±0.008(n=13)forpaddyfields.Theutilizationrateofgrasslandswas0.959±0.015(n=10),whichwasclearlyhigherthanthatofotherhabitatsatthelatewinteringstage.Theutilizationratewas0.033±0.011(n=10)forshallow-waterareasand0.008±0.007(n=10)formudflats.Thepaddyfieldswerenotutilized(Fig.2).Themajorhabitattypesutilizedbythegooseguildincludeddeep-waterandshallow-waterareas,mudflatsandpaddyfields.Thegrasslandhabitatwasmainlyutilizedattheearlywinteringstage,withautilizationrateof0.627±0.036(n=15),followedbyshallow-waterareasof0.201±0.033(n=15),paddyfieldsof0.161±0.038(n=15),deep-waterareasof0.009±0.005(n=15)andmudflatsof0.001±0.000(n=15).Atthemiddlewinteringstage,theutilizationratewas0.491±0.069(n=13)forgrasslands,0.323±0.059(n=13)forshallow-waterareas,0.147±0.069(n=13)formudflatsand0.034±0.018(n=13)forpaddyfields.Thedeep-waterareaswererarelyutilized,withautilizationrateof0.004±0.004(n=13).Atthelatewinteringstage,themajorhabitatutilizedwasgrasslandwithautilizationrateof0.616±0.072(n=10),followedby0.277±0.052(n=10)fortheshallow-waterareaand0.107±0.051(n=10)forthedeep-waterarea.Themudflatandpaddyfieldhabitatswerebasicallynotutilized(Fig.3).Attheearlywinteringstage,significantdifferencesforhabitatutilizationratesbetweentheHoodedCraneandgooseguildwerefound(deep-water:df=28,Z=-2.105,p=0.035;shallow-water:df=28,t=3.505,p=0.002;mudflat:df=28,t=-2.931,p=0.007;paddyfield:df=28,t=-2.686,p=0.012)inthefivetypesofhabitatsexceptforgrassland(df=28,t=1.849,p=0.075).Significantdifferenceswerealsoobservedintheutilizationratesofshallow-waterhabitatatthemiddlewinteringstage(df=24,Z=-2.590,p=0.010),butnotinotherhabitats(deep-water:df=24,Z=-1.000,p=0.317;mudflat:df=24,t=-1.690,p=0.104;grassland:df=24,t=0.403,p=0.690;paddyfield:df=24,Z=-0.633,p=0.526).Extremelysignificantdifferenceswerefoundintheutilizationofthedeep-waterareas,shallow-waterareasandgrasslandsatthelatewinteringstage(df=18,Z=-2.796,p=0.005;df=18,t=4.382,p=0;df=18,t=-4.436,p=0,respectively).Nosignificantdifferencewasfoundintheutilizationofthemudflats(df=18,Z=-1.000,p=0.317)(Table1).atthelate階段ThewidthofthespatialnicheofHoodedCranesandgooseguildvariedduringthewinteringstage.ThisnichewidthoftheHoodedCraneswas1.057attheearlystage,1.099atthemiddlestageand0.191atthelatestage.Thewidthofthespatialnichewasthehighestatthemiddlestage,followedbytheearlyandlatestages.Thewidthofthespatialnicheofthegooseguildwas0.959attheearlystage,1.133atthemiddlestageand0.893atthelatestage.Thewidthwasthehighestatthemiddlestage,followedbytheearlyandlatestages(Table2).AdifferencewasfoundinthenicheoverlapoftheHoodedCraneandgooseguildatthethreewinteringstages.Thegreatestnicheoverlapwas0.914foundatthelatestage,followedby0.906atthemiddlestageand0.854attheearlystage(Table2).子階段tatutilizationofficiensi晶ssafranetalWaterbirdshavetoselectsuitablehabitatswhenfacingconstantlychanginghabitatsduringthewinter(WarnockandTakekawa,1995;LongandRalph,2001;Beerensetal.,2011).Resourcepartitioningisrelatedtoitsavailabilityinhabitats(KoberandBairlein,2009).Forthewaterbirdsassemblinginflocks,theavailabilityofresourcesisanimportantfactoraffectingflockdynamics(Gawlik,2002).Therefore,changesinresourceavailabilitywouldcausedynamicchangesofthenicheofwaterbirds(Pearmanetal.,2008).Whenthenumberofsuitablehabitatsisreduced,theutilizationofotherhabitatswillinevitablyincreaseasacompensationforhabitatloss(Gerstenberg,1979;WarnockandTakekawa,1995;LongandRalph,2001).Inourstudy,thevariationinwaterlevelandseasonalchangesofvegetationstructureandhumanactivitiesjointlyaffectedtheavailabilityofwetlandresourcesatShengjinLake.Thus,thecharacteristicsofhabitatsandmicrohabitatswouldchange,furthercausingdynamicchangesinhabitatutilizationandwidthofthespatialnicheoftheHoodedCraneandgooseguild.Habitatandfoodavailabilityofwaterbirdsiscloselyrelatedtowaterlevels(Safranetal.,2000;Zhaoetal.,2010).AtthemiddlewinteringstagewhentheHuangpenSluicewasopenedforfishing,thewaterlevelofShengjinLakedroppedquicklyandlargeareasofmudflatsbecameexposed.Theundergroundpartsofsomeaquaticplantswerereadilyaccessed,whichwasfavorableforbothcranesandgeese.Atthelatewinteringstage,thewaterlevelrosesubstantiallyduetothecontinuousrainfallinthespring,whichsubmergedmostofthemudflatsandpartofthegrasslands.Thehabitatsreadilyutilizedbythewaterbirdswerereducedandthewidthofthespatialnicheswasnarrowed(Table2).Theseasonalchangesofvegetationstructuremightinducechangesinthestrategyofresourceutilizationonthepartofbirds(Kushlan,1981;ThomsonandFerguson,2007).Attheearlystage,vegetationflourishedinthegrasslands.Thetemperaturedeclinedatthemiddlestageandthewitheringofplantsreducedtheavailablityoftheabovegroundpartsofplantstowaterbirds.Therefore,thehabitatutilizationofthegrasslandsbyHoodedCranesandgeesewassomewhatreducedatthemiddlestage(Figs.2,and3).Duringthelatestage,thevegetationinthegrasslandsbegantogerminate,providingfavorableforaginghabitatsforgrazingwaterbirds.Grasslandreclamationinwetlands,livestockgrazingandanenclosurecultureresultedinhabitatloss,whichloweredtheresourceavailabilityforwaterbirds(Wangetal.,2011).Resource-exploitingaquacultureresultedinseveredegradationofsubmergedvegetation,animportantfoodsourceforwaterbirds(Xuetal.,2008).Agriculturalactivitiesbyfarmersusuallyinterferedwiththebehaviorpatternandforagingrateofwaterbirds(Luoetal.,2012).Waterbirdsforaginginthepaddyfieldshadtofaceconsiderablelevelsofdisturbance(Reifetal.,2008).Attheearlystage,thericegrainswerescatteredathighdensityoverthenewly-harvestedfieldswithfewhumandisturbances.Therefore,thepaddyfieldsweremuchutilizedbythecranesandgeese.Atthemiddlestage,humandisturbancesinthefields,whichhadbeencultivatedandchangedtowheatfields,increasedinintensity.Simultaneously,themiddlestagewasalsoastageformassivefishing.Thefishermenusuallyexplodedfirecrackerstodrivethewaterbirds(mainlyPhalacrocoraxcarbo)awayfromtheircageandpondaquaculture,causingtheutilizationratetodeclineinthepaddyfieldsbythecranesandgeese.Atthelatestage,thefrequentagriculturalactivitiesanddispellingactivitiesmayhaveaddedtothedifficultyoffoodresourceutilizationbywaterbirdsinthepaddyfieldcultivatedintowinterwheat(Figs.2and3).Thedensityofricegrainsscatteredinthefieldsdeclinedasaresultofconsumptionandsoilturning(Leeetal.,2001;Amanoetal.,2006).Ifthishappened,thepaddyfieldhabitatswereabandonedgraduallybythecranesandgeese.utilizationsoinractssiphenthractutilizationsWhenthefoodresourceswerelimited,thewaterbirdsconcentratedwithinthislimitedspacetosearchforavailablefoodsources,whichincreasednicheoverlapandintensifiedresourcepartitioning(KoberandBairlein,2009).ThewidthofthespatialnicheoftheHoodedCranesandgooseguildpresentedsimilartendenciesofdynamicchangeindifferentwinterperiods(Table2).Thisindicatesthattheyhadsimilarrequirementsfortheresources,therebyleadingtoresourcepartitioning.Thewidthsofthespatialnicheofthegooseguildatallstageswereallhigherthanthoseofthecranesexceptattheearlywinteringstage.ThisshowsthatthespatialnicheoftheHoodedCraneswasrestrictedduetotheinterspecificcompetition,comparedwithgeeseinalargergroup(O’Connoretal.,1975).HoodedCranesandgeesesharedfourcommonhabitattypesatShengjinLake,i.e.,shallow-waterareas,mudflats,grasslandsandpaddyfields.Bothusedthegrasslandsintensivelywithsubsequenthighutilizationrates(Figs.2and3),showingthatthegreatesthabitatcompetitionoccurredinthegrasslands.Significantdifferenceswerefoundintheutilizationratesofallhabitatsattheearlyandlatestagesbythecranesandgooseguild(Table1).Thissuggeststheseparationinspace,especiallywhentheresourcewasinsufficient.Itisaresultofdifferentpatternsofresourceutilizationbycoexistingspecies(Oksanen,1987).Ithassomethingtodowiththefeedingbehaviorofthesecranesandgeese,which,inturn,isdeterminedbythemorphologyofbirds,suchasthelength,widthandshapeofthebill(KoberandBairlein,2009;AplinandCockburn,2012).WediscoveredinoursurveythatHoodedCranesforagedbydiggingouttheundergroundtubersofplants.Thegeesemainlyfeedbybitingtheabovegroundpartsofplants.Therewasspatialseparationbetweenthecranesandgooseguild.Spatialseparationreducestheintensityofresourcepartitioning(González-Solísetal.,2007).Attheearlywinter,besidesgrasslandhabitat,theHoodedCranesalsohadahighutilizationrateinthepaddyfields.ThegrasslandwithitsabundantCarexwasthemainhabitatutilizedbythegoosespecies.OnlyasmallnumberofBeanGeeseutilizedthepaddyfields.BecausetheGreaterWhite-frontedGooseisahabitatspecialistinChina,itpreferstograzeonshort-swardrecessionalCarexsedgemeadows.TheLesserWhitefrontedGoosehasashortbillandthereforefavorsgrasslandwhereCarexsedgesgrow(Zhaoetal.,2012;Wangetal.,2012).TheirnumberwaslowandunstableatShengjinLake(Chengetal.,2009;Wangetal.2012).Atthelatewinteringstage,thewaterlevelrosemarkedlyandthetemperatureincreased.Asswimmingbirds,geesepreferawaterhabitat.Butthecranesweremostlyconcentratedinthegrasslands(Figs.2and3,Table1