寧夏中部干旱帶退化草地圍封效應(yīng)的研究.pdf

1、寧夏大學(xué)博士學(xué)位論文寧夏中部干旱帶退化草地圍封效應(yīng)的研究姓名：王蕾申請(qǐng)學(xué)位級(jí)別：博士專業(yè)：草業(yè)科學(xué)指導(dǎo)教師：謝應(yīng)忠201103IIAbstractEnclosureasaneconomicaleffectivemethodfdegradedgrasslecologicalrestationiswidelyusedinthegrasslrestationgovernance.Grasslaccountsfnearly50%ofthelar

2、eainNingxia.Degradedgrassldirectlyrestrictstheregionaleconomicdevelopment.Theecologicalsafetyhadbeenthreatenedbydegradedgrassl.Since2003grasslrecoveryhasachievedremarkableresults.YanchicountylocatedatthesouthwestedgeofMu

3、UssylisatransitionzonebetweentheErdosPlateautheLoessPlateauisanecotonecomprisingsylthroughtodesertsteppetosteppe.Overtherecentdecadesithassufferedseveresydesertification.TheexperimentwascarriedoutinYanchiin2010.Thechange

4、sofvegetationsoilpropertiessoilseedbanklitteramongdifferentyearsofenclosuretheunenclosedgrasslwerecarriedout.Themainresultswereasfollows:Thecommunitycompositionhasvariedafterenclosure.Ephemerereumsemishrubsgraduallygavep

5、lacetoperennialherbs.Communityyieldmeanheighthasincreasedwiththeenclosingtimeincreasing.Vegetationcoveragecommunitydensityreachedamaximumatthe5thyearthendeclined.Withincreasedperiodsofexclosurespeciesdiversityreachedamin

6、imumatthe5thyearthenincreased.Theperennialherbsweredominatinspeciescompositionofsoilseedbank.Thedensityofsoilseedbankswerebetween190690seedsm2respectivelyindifferentyearsofenclosure.WithincreasedperiodsofexclosureThedens

7、ityofsoilseedbankreachedamaximumatthe5thyearthendeclined.Similarityindexofsoilseedbankthevegetationwaslowindifferentyearsofenclosure.Thegroundvegetationdensitydensityofsoilseedbankweresignificantlycrelatedindifferentyear

8、sofenclosure.Thesoilwatercontentreachedamaximumatthe6thyear.ChangesofdynamicsofsoilbulkganicmattertotalnitrogenpHhadnoobviouslawwiththeenclosingtimeincreasing.Withincreasedperiodsofexclosureavailablenitrogenavailablekali

9、umavailablephosphtotalsalinityreachedamaximumthendeclined.Soilwatercontentganicmattertotalnitrogenwerehigherin520cmdepththanthosein05cmdepthindifferentyearsofenclosure.AvailablekaliumpHwerehigherin05cmdepththanthosein520

10、cmdepthindifferentyearsofenclosure.Thenumberofbacteriafungiactinomycetestotalmicrobehasincreasedwiththeenclosingtimeincreasing.Activitiesofcatalaseureaseinvertasehadnoobviouslawwiththeenclosingtimeincreasing.Withincrease

11、dperiodsofexclosureactivitiesofalkalinephosphataseincreased.Withincreasedtimeslitteraccumulationreachedamaximumat9th10thmonthsthendeclined.ThelitterdecompositionrateswasgraduallydecreasedwiththetimeThelitterdecomposition

12、ratesoftheenclosedgrasslwashigherthanthatoftheunenclosed.Withincreasedtimesnaturalwaterholdingratesoflitterreachedamaximumthendeclined.Boththetotalnitrogencontentoflitterthetotalphosphcontentoflitteroftheenclosedgrasslwe