简介:Throughthemethodsofcorrelationanalysisandmainfactoranalysis,therelationshipbetweenthepoplarINAbacterialcankerandcircumstanceswasanalyzedand9mainfactorsforaffectingthediseasewereselected.Basedonthecomprehensiveanalysisofmainfactorsandinducedfactors,thestandardforriskgradesofthisdiseasewaspromotedandnortheastregionofChinawasdividedinto4districtswithdifferentriskgrades:seriouslyoccurringdistrict,commonlyoccurringdistrict,occasionallyoccurringdistrict,andun-occurringdistrict.NonlinearregressionanalysisforsixmodelcurvesshowedthattheRichardgrowthmodelwassuitablefordescribingthetemporaldynamicsofpoplarINAbacterialcanker.Bystepwisevariableselectionmethod,themulti-variablelinearregressionforecastingequationwassetuptopredictthenextyear'sdiseaseindex,andtheGM(1,1)modelwasalsosetupbygreymethodtosubmitmiddleorlongperiodforecast.
简介:Background:Climatechangetriggeredmanystudiesshowingthattrendsandeventsofenvironmentalconditionscanreducebutalsoaccelerategrowthatthestandandindividualtreelevel.However,itisstillratherunknownhowclimatechangemodifiesthegrowthpartitioningbetweenthetreesinforeststands.Methods:Basedonlong-termgirth-tapemeasurementsinmaturemonospecificandmixed-speciesstandsofNorwayspruce(Piceaabies(L.)Karst.)andEuropeanbeech(FagussylvaticaL.)wetracedtheeffectoftheseveredroughtsin2003and2015fromthestand-downtothetreelevel.Results:StandgrowthofNorwaysprucedecreasedbyabout30%intheonce-in-a-centurydrought2015,whileEuropeanbeechwasmuchmoredroughtresistant.Wateravailabilitygenerallyamplifiedsize-asymmetricgrowthpartitioning.EspeciallyincaseofNorwaysprucewateravailabilityprimarilyfosteredthegrowthofpredominanttrees,whereasdroughtfavouredthegrowthofsmalltreesattheexpenseofthepredominantones.Wecouldnotdetectsignificantdifferencesbetweenmixedandmonospecificstandsinthisregard.Conclusions:Thedrought-inducedreallocationofgrowthinfavourofsmalltreesincaseofsprucemayresultfromitsisohydriccharacter.Wehypothesizethatassmalltreesareshaded,theycanbenefitfromthereducedwaterconsumptionoftheirsun-exposedtallerneighbours.Incaseofbeech,asananisohydricspecies,talltreessufferlessandsmallertreesbenefitlessunderdrought.Thediscussionelaboratestheconsequencesofthewaterdependentgrowthallocationforforestmonitoring,growthmodelling,andsilviculture.
简介:Inthecontextofglobalcarboncyclemanagement,accurateknowledgeofcarboncontentinforestsisarelevantissueincontemporaryforestecology.Wemeasuredtheabove-groundandsoilcarbonpoolsinthedarkconiferousborealtaiga.Wecomparedmeasuredcarbonpoolstothosecalculatedfromtheforestinventoryrecordscontainingvolumestockandspeciescompositiondata.Theinventorydataheavilyunderestimatedthepoolsinthestudyarea(StolbyStateNatureReserve,centralKrasnoyarskTerritory,RussianFederation).Thecarbonpoolestimatedfromtheforestinventorydatavariedfrom25(tha-1)(low-densitystands)to73(tha-1)(highlystockedstands).Ourestimatesrangedfrom59(tha-1)(lowdensitystands)to147(tha-1)(highlystockedstands).Ourvaluesincludedlivingtrees,standingdeadwood,livingcover,brushwoodandlitter.Wefoundthattheproportionofbiomasscarbon(livingtrees):soilcarbonvariedfrom99:1to8:2forfullystockedandlow-densityforeststands,respectively.Thiscontradictsthecommonunderstandingthatthebiomassintheborealforestsrepresentsonly16–20%ofthetotalcarbonpool,withthebalancebeingthesoilcarbonpool.
简介:条件价值评估法(CVM)是目前唯一能获知环境资源的全部经济价值,包括使用和非使用价值。CVM评估环境物品价值原理是通过假想市场来了解消费者对具体的一个环境物品的偏好,并通过支付意愿而表现出来。CVM调查过程中,为了获得消费者对环境物品价值的偏好,必须通过各种诱导技术。不同的诱导技术可产生不同的支付意愿结果。本研究通过评估越南巴为国家森林公园生态旅游非使用价值来比较CVM中的两分式(DC)和支付卡(PC)诱导技术。通过本研究结果,得出以下的结论:(1)DC技术获得的支付意愿(wTP)和参与者的“同意”支付都高于PC技术;(2)CVM完全可以应用于环境物品非使用价值评估领域。