简介:探索研究流域非点源氮污染控制的有效措施,对于治理改善水环境恶化具有重要的现实和长远意义。以山美水库流域为研究区域,建立AnnAGNPS氮污染模型,通过情景模拟技术分别模拟了河岸缓冲带、适量施肥、免耕、少耕、梯田和退耕还林等最佳管理措施的非点源氮污染削减效率。结果表明:(1)梯田与退耕还林对氮的削减率较高,均高于15%;免耕较低,为13%;少耕、合理施肥、河岸缓冲带削减效果有限,低于10%。(2)河岸缓冲带、少耕、免耕、梯田等措施的总氮削减率在不同月份的变化趋势与泥沙削减变化趋势一致,在7月和8月有较高的削减率;合理施肥与退耕还林的总氮削减率则与流域施肥状况相关性更高,在2—4月份有较高的削减率,因此山美水库流域水环境改善应结合非点源氮污染治理和流域水土流失治理。
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简介:Glacierinventorycompilationduringthepast20yearsandmodificationsofthatfortheEasternPamirandBanggongLakeindicatethatthereare46,342modernglacierswithatotalareaandvolumeof59415km2and5601km3respectivelyinChina.Theseglacierscanbeclassifiedintomaritimeandcontinental(includingsub-continentalandextremelycontinental)types.ResearchesshowthatglaciersinChinahavebeenretreatingsincetheLittleIceAgeandthemasswastagewasacceleratedduringthepast30to40years.BeinganimportantpartofglaciologicalstudiesinChina,icecoreclimaticandenvironmentalstudiesonTibetanPlateauandintheAntarcticahaveprovidedabundant,highresolutioninformationaboutpastclimaticandenvironmentalevolutionovertheTibetanPlateauandAntarctica.ExceptfordifferentparametersrecordedinicecoresrelatingtoclimateandenvironmentchangesonTibetanPlateau,recordsfromicecoresextractedfromdifferentglaciersshowthatthediscrepanciesinclimaticandenvironmentalchangesonthenorthandsouthpartsoftheplateaumaybetheconsequenceofdifferentinfluencingeffectsfromterrestrialandsolarsources.GlaciologicalandmeteorologicalphenomenaimplythatLambertGlaciervalleyisanimportantboundaryofclimateintheeastAntarctica,whichisthoughttobeconnectedwithcyclonicactivitiesandCircum-polarWavesovertheAntarctica.
简介:PermafrostinChinaincludeshighlatitudepermafrostinnortheasternChina,alpinepermafrostinnorthwesternChinaandhighplateaupermafrostontheTibetanPlateau.Thehighaltitudepermafrostisabout92%ofthetotalpermafrostareainChina.Thesouthboundaryorlowerlimitoftheseasonallyfrozengroundisdefinedinaccordancewiththe0℃isothermallineofmeanairtemperatureinJanuary,whichisroughlycorrespondingtothelineextendingfromtheQinlingMountainstotheHuaiheRiverintheeastandtothesoutheastboundaryoftheTibetanPlateauinthewest.SeasonalfrozengroundoccursinlargepartsoftheterritoryinnorthernChina,includingNortheast,North,NorthwestChinaandtheTibetanPlateauexceptforpermafrostregions,andaccountingforabout55%ofthelandareaofChina.Thesouthernlimitofshort-termfrozengroundgenerallyswingssouthandnorthalongthe25°northernlatitudeline,occurringinthewetandwarmsubtropicmonsoonclimaticzone.Itsareaislessthan20%ofthelandareaofChina.
简介:中国是一个洪水多发国家,洪水灾害平均每年给中国造成约千亿元的直接经济损失。成功的洪水风险管理离不开公众的参与,了解公众对环境风险的认知是设计有效风险沟通策略的关键,也是促进公众认识提升与行为转变的重要环节。本研究回顾了公众对洪水风险的相关认知,系统梳理了风险认知研究范式、洪水风险认知的测量及其影响因素。现有研究表明,公众居住地的地理特征与洪水风险认知存在显著的相关关系:居住地距离洪水风险源越近,洪水风险认知越高;居住地相对洪水风险源海拔越高,洪水风险认知越低。女性、年龄较高的人群更关注洪水风险,而教育程度、收入水平与洪水风险认知则没有显著相关关系。受灾经历是影响洪水风险认知的重要因素,有过受灾经历的公众会有较高的洪水风险认知和较强的应对灾害的行为。公众对洪水风险管理的信任程度也将影响公众的洪水风险认知。本研究对洪水风险认知的测量指标和测量方法做了梳理和评述,并提出今后洪水风险认知研究可能拓展的方向,如探索公众洪水风险认知对行为改变的作用,以及对洪水风险管理的影响。
简介:植被格局是指植被在生活空间中的位置和布局状况,是物种生物学特性和外界环境因子综合作用的结果。湿地植被在景观上总是沿着某个环境梯度呈较明显的带状分布特点,但是关于带状分布形成的机理目前还不是很清楚。大量事实表明,湿地植被格局不仅受制于湿地自身自然环境状况(包括非生物和生物因素),同时也取决于湿地植物种的生物学特性,并且受到人类干扰活动的影响。具体成因如下:非生物因素主要包括气候、地貌、水文和土壤等,这些因素通过对水、热、光和营养等因子的分配而在不同尺度上影响湿地植被的组成和分布,其中,水位和盐度梯度分别是淡水和盐沼湿地植被格局形成的主导因子。生物因素主要包括竞争和植食作用,高竞争力物种采用迅速繁殖和扩散的策略成为优势物种直接影响植被的分布,植食作用则可能通过改变植物间竞争关系而影响植物分布。物种生物学特性主要包括胁迫忍耐力及繁殖和定居能力等,如洪水忍耐力高的物种往往分布在最高水位的区域,繁殖和定居能力强的物种能使自身在复杂环境下取得竞争优势。人类活动可以通过改变湿地生态系统中的非生物因素和生物因素的相互关系来影响植被分布格局。针对当前研究的现状,今后的研究应在淡水湿地系统植被成因,生物因素如植物间相互作用以及植物自身关系的权衡对格局的影响,微生物作用对植被格局的影响,野外控制实验四个方面进一步加强。
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简介:Sandydesertificationislanddegradationcharacterizedbywinderosionmainlyresultedfromtheexcessivehumanactivitiesinarid,semiaridandpartofsub-humidregionsinnorthernChina.Theresearchonsandydesertificationhasexperiencedmorethan5decadesofarduouscourseofthestrugglealongwiththeestablishmentanddevelopmentofChina′sdesertscience.Researchesinthisfieldhavemadeagreatcontributiontothenationaleconomicconstruction,andenvironmentalprotection.Thispaperfocusesonpresentingthemajorprogressandachievementsinthesandydesertificationresearchduringthelast50years,includingthestagesofstudyonsandydesertification,backgroundenvironmentofsandydesertificationanditschanges,theconception,causes,process,monitoringandassessmentofsandydesertification,thevegetationsuccession,landscapeecology,plantphysiology,impactsonecosystem,high-effectiveuseofwaterandlandresourcesandsustainabledevelopmentinsandydesertifiedregions,sandydesertificationcontrolmodelsandtechniquesetc.
简介:2007年4-7月,采用野外直接观察和样方法在北京野鸭湖湿地自然保护区对金眶鸻(Choradriusdubius)的巢址进行了调查研究。金眶鸻于4月中上旬迁来野鸭湖,5月初开始产卵。野外共发现金眶鸻的巢45个,其中水库岸边28个,岛上17个。逐巢进行了常规测量,并对巢址及附近无巢区域的生境进行了调查。通过主成分分析和独立样本t检验,结果表明,影响金眶鸻巢址选择的主要因子依次是植被盖度、植物种类、植被密度、距水源的距离、植被高度最大值、干草比例等。这说明金眶鸻倾向于在植被物种丰富度较高、植被较高、密度和盖度较大、距水源较近的地方营巢。巢址选择除了与隐蔽、食物、水、种内竞争等有关外,还与巢的保温性能有关,而巢的隐蔽性与食物是其中的关键因素。