简介：Background:WithfarmlandafforestationbecomingcommonpolicyinmanyEuropeanUnioncountries,westudiedhowearlyforestsuccession(frommeadowtoyoungstand)influencessmallmammalspeciescomposition,diversity,abundanceandbiomass.Despitenumerousinvestigationsintoforestsuccession,almostnoattentionhasbeengiventothesmallmammalcommunitychangeintheearly-successionalforestecosystems,startingwiththepre-foresthabitatandendingwithstandformationandtheestablishmentoftreedominance.Wecomparedsmallmammalcommunitiesinmeadowsattheinitialstageofregrowth(withsaplingslessthan10cminheight),inyoungforest(5–10yearsold)andmoreadvancedforest(15–20years)inbothcasesofhuman-inducedforestsuccession,wherethetreeshadbeenplanted,andnaturalforestsuccession,wherenaturalregrowthofmeadowshadoccurred.Results:Thegreatestdiversityofsmallmammalspecieswasrecordedinthemeadow(H=2.95),withalowerdiversityfoundintheyoungforest(H=2.61)andevenlowerintheadvancedforest(H=2.04),thelasthabitatbeingthemostmonodominantic.TheorderofspeciesdominancefromMicrotussp.(M.arvalis,M.agrestis),Myodesglareolus,Apodemusflavicollis,Sorexaraneus,A.agrariusinthemeadowchangedtoM.glareolus,S.araneus,M.arvalis,M.agrestisintheyoungforestandtoM.glareolus,A.flavicollis,S.araneusintheadvancedforest.Thelowestrelativeabundanceofsmallmammalswasrecordedinthemeadow(18.19±2.27ind.Per100trap-days),withMicrotusvolesbeingthemostabundant.Relativeabundancewashigherintheyoungforest(22.72±2.25ind.Per100trap-days),withMyodesglareolusbeingthemostabundant(7.59±0.96ind.Per100trap-days)andatitshighestintheadvancedforest(23.91±2.77ind.Per100trap-days),againwithM.glareolusbeingthemostabundant(15.54±2.35ind.Per100trap-days).Conclusions:Thus,ouranalysissuggeststhatthatduringearlymeadow-forestsuccession,thediversityofthe

简介：对土地资源及其综合生产潜力的评价，在于阐明特定时空土地资源的性质、特点、生产潜力和利用价值的水平，为合理利用土地、充分挖掘生产潜力提供科学依据；对于地形起伏大、生态环境脆弱、土地类型丰富，但总体质量偏低的北京石质山区的进一步治理、规划和建设来说，显得尤为重要，亦有着鲜明的实际意义．该文在分析土地评价概念的基础上，界定了土地综合生产潜力的内涵，利用模糊数学、统计学、系统分析等手段，采用定性和定量分析相结合的方法，结合北京石质山区特定时空上土地单元的自然及社会属性，对土地综合生产潜力评价指标选取的基本条件、构建指标体系的基本原则和方法等加以探讨，提出了土地综合生产潜力评价模型，并应用于密云水库上游黄峪口小流域，得到理想效果．

简介：Saturatedhydraulicconductivity(Ks)isanimportantsoilhydraulicparameterforcharacteringtherateofwaterflowacrossthesoilsandismainlyrelatedtoitshighspatialvariability.Inasmallwatershedwiththeareaof0.27km2intheLoessPlateau,Ksof197soilsamplesunderdifferentvegetationsandlandformsweremeasured.Kshadamoderatevariabilityfortotalsamples.TheforestlandhadhighKswithlowcoefficientofvariation(CV),butthegrasslandinthewatershedbottomhadlowKswit...

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简介：密云水库集水区水源保护林在北京地区饮用水源保护中起着非常重要的作用．本文给出了该区小流域对比实验的初步研究结果，有林小流域和无林小流域对１９９６年７月３０日降雨过程较为一致的径流响应表明，土壤前期含水量对流域产流有较大的影响，在降雨较多土壤含水量较大的情况下该区产流方式可以表现为饱和地表径流．尽管该区以霍顿超渗产流为主，但对于１９９７年７月３１日至８月１日降雨过程，森林流域产流总量为１３９３．８０ｍ３，无林流域为２２０２．４３ｍ３，森林流域减少洪水总量３６．７％，消减洪峰流量达３７３％．然而，１９９７年７月１９日降雨过程森林流域径流洪峰量与洪水泥沙含量均较无林流域高，这表明预处理措施对径流泥沙过程有极为显著的影响

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：黄家二岔小流域地处中国黄土高原水土流失最严重的黄土丘陵沟壑区，自１９８３年以来，该小流域作为小流域治理和农业发展技术的试验示范基地，开展了一系列小流域治理和农业综合发展技术的试验研究工作．本文主要介绍了黄家二岔小流域不同治理阶段所存在的问题、目标、研究思路、内容、技术措施、成果和经验，以期对处在不同发展时期的我国和其他发展中国家的流域治理工作提供参考和借鉴．