简介：50年来，由于人类活动对水、土、植被等资源的强烈干扰，民勤绿洲的生态环境发生了巨大的变化，主要表现为：地表水资源减少，水量从20世纪50年代的4．5亿m^3减少到90年代的0．89亿m^3；地下水量过度开采，水位下降，从20世纪50年代的1．5～2．0m下降到80年代的5．0m，90年代的16．4m；水质污染，矿化度升高；天然和人工植被衰退，物种多样性减少，植被向旱生方向演替；土壤早化加剧，土地荒漠化严重等。为探索解决这一系列问题，在定量分析长期野外观测资料的基础上，主要分析了近50年来民勤绿洲水资源变化过程及其态势以及水资源的不合理利用所引起的一系列生态环境变化，同时提出主要治理途径：1）以流域为单元，通过法律、行政和经济手段强化水资源管理；2）通过节水技术应用，发展节水型农业和建立节水型社会；3）增加外流域调水量，满足生态环境用水需求；4）实施适度移民，实现人与自然和谐发展；5）运用生物和工程措施，综合防治荒漠化，整治土壤盐溃化。

简介：Aerobicstaticpilecomposting(mechanicalturningevery3days)ofpigmanurewaspreparedat8m3windrowheaps.Sawdustwasusedasthebulkingagenttoprovideadditionalcarbonandtoincreasetheporosityofthesubstrate.TwotreatmentsatinitialC/Nratiosof30and15,respectively,weredesignedinthestudy.Dissolvedorganiccarbon(DOC),solubleNH4+-N,C/Nratiosinsolidandaqueousphases,E4/E6ratios,andseedgerminationindex(GI)weredeterminedtoevaluatethematurityoftheco-composts.Seedgerminationindex,abiologicalparameter,wassuggestedasoneofthemostreliablematurityindicatorsfororganiccompost.TheresultsshowedthatthetreatmentattheinitialC/Nratioof30reachedmaturityafter49daysofcomposting;however,thetreatmentattheinitialC/Nratioof15shouldrequirecompostingtimeoflongerthan63daystoobtainmaturation.Chemicalmulti-indicatorevaluationwasnecessary,andtheGImeasurementwastherecommendedapproachformaturityevaluationinthestudy.

简介：为了使基于人工模拟降雨装置的水土保持试验更可靠,采用人工降雨试验方法,通过研究QYJY-503C人工模拟降雨装置的降雨特性,探讨该装置在水土保持科学试验中的适用性。结果表明：1）雨滴达到终速时雨滴-色斑直径的关系为d=0.3839D0.709;2）QYJY-503C人工模拟降雨装置有效降雨均匀度超过80%;3）在试验范围内,雨滴直径随降雨强度增大而增大,雨滴中数直径与降雨强度呈d50=0.5595I0.2805的幂函数关系,相同降雨强度条件下的雨滴直径较天然雨滴偏小20%~70%;4）降雨动能与降雨强度呈E=0.0042I-0.021的线性关系,可通过控制降雨强度实现降雨动能与天然降雨的相似性;5）QYJY-503C人工模拟降雨装置性能稳定、可控性强,可适用于室内土壤侵蚀的研究。

简介：Thechloroformfumigation-incubationmethowasusedtomeasurthesoilmicrobialbiomassC(SMBC)andN(SMBN)in16loessialsoilssampledfromAnsai,YongshouandYanglinginShaanxiProvince.TheSMBContentsinthesoilsrangedfrom75.9to301.0μgCg^-1withanaverageof206.μgCg^-1,accountingfor1.36%-6.24%ofthetotalsoilorganicCwithanaverageof3.07%,andtheSMBNcontentsfrom0.51to68.40μgNg^-1withanaverageof29.4μgNg^-1,accountingfor0.20%-5.65%ofthetotalNinthesoilswithanaverageof3.36%.AcloserelationshipwasfoundbetweenSMBCandSMBN,andtheybothwerepositivelycorrelatedwithtotalorganicC,totalN,NaOHhydrolizableNandmineralizableN.Theseresultsconfirmedthasoilmicrobialbiomasshadacomparativeroleinnutrientcyclesofsoils.

简介：Fivehumicfractionswereobtainedfromauniformly^15N-labelledsoilbyextractionwith0.1molL^-1Na4P2O7,0.1molL^-1NaOH,andHF/HCl-0.1molL^-1NaOH,consecutively,andanalyzedby^13Cand^15NCPMASNMR(crosspolarizationandmagicanglespinningnuclearmagneticresonace).Comparedwiththoseofnativesoilshumicfractionsstudiedasawholecontainedmorealkyls,methoxylsandO-alkyls,being27%-36%,17%-21%and36%-40%,respectively,butfeweraromaticsandcarboxyls(bein14%-20%and13%-90%,respectively),Amongthosehumicfractions,thehumicacid(HA)andfulvicacid(FA)extractedby0.1molL^-1Na4P2O7containedslightlymorecarboxylsthancorrespondinghumicfractionsextractedby0.1molL^-1NaOH,andtheHAextactedby0.1molL^-1NaOHaftertreatmentwithHF/HClcontainedtheleastaromaticsandcarboxyls.Thedistributionofnitrogenfunctionalgroupsofsoilhumicfractionsstudiedwasquitesimilartoeachotherandalsoquitesimilartothatofhumicfractionfromnativesoils.Morethan75%oftotalNineachfractionwasinamidefrom,with9%-13%presentasaromaticand/oraliphaticaminesandtheremainderasheerocyclicN.

简介：Theannualseriesofδ13CweremeasuredintreeringsofthreeCryptomeriafortuneidisks(CF-1,CF-2,andCF-3)collectedfromWestTianmuMountain,ZhejiangProvince,China,accordingtocross-datingtreeringages.Therewasnoobviousdecreasingtrendoftheδ13CannualtimeseriesofCF-2before1835.However,from1835to1982thethreetreeringδ13Cannualseriesexhibitedsimilardecreasingtrendsthatweresignificantly(P≤0.001)correlated.Thedistributioncharacteristicsofascatterdiagrambetweenestimatedδ13CseriesofCF-2frommodelingandtheatmosphericCO2concentrationextractedfromtheLawDomeicecorefrom1840to1978wereanalyzedandacurvilinearregressionequationforreconstructingatmosphericCO2concentrationwasestablishedwithR2=0.98.Also,atestofindependentsamplesindicatedthatbetween1685and1839thereconstructedatmosphericCO2concentrationusingtheδ13CseriesofCF-2hadacloserelationshipwiththeLawDomeandSipleicecores,withastandarddeviationof1.98.ThegeneralincreasingtrendofthereconstructedatmosphericCO2concentrationcloselyreflectedthelong-termvariationofatmosphericCO2concentrationrecordedbothbeforeandaftertheIndustrialRevolution.Between1685and1840theevaluatedatmosphericCO2concentrationwasstable,butafter1840itexhibitedarapidincrease.Givenalongerδ13Cannualtimeseriesoftreerings,itwasfeasibletorebuildarepresentativetimeseriestodescribetheatmosphericCO2concentrationforanearlierperiodandforyearsthatwerenotintheicecorerecord.