简介:Exclosureisamethodofrehabilitatingdegradedlandsbyprotectingthemfromtheinterferenceofanimalsandfromhumanencroachment,andisusedtoregeneratenativevegetationasawaytoreducesoilerosion,increaserainwaterinfiltrationandprovidefodderandwoodybiomassindegradedgrazinglands.Therefore,westudiedwoodyplantstructure,diversityandregenerationpotentialsin5-and10-yeargrazingexclosuresincomparisonwithopengrazedsitesinasemi-aridenvironment.Dataonspeciesdiversity,abundance,structure,basalarea,frequency,density,andregenerationstatuswerecollectedfrom270sampleplots.Forty-onewoodyspeciesrepresenting20familieswereidentified,with18,28and38speciesfoundinopengrazedareas,andin5-and10-yeargrazingexclosures,respectively.The10-yeargrazingexclosureshadahigher(P<0.05)speciesrichnessandplantdensitiescomparedtothe5-yeargrazingexclosuresandtheopengrazedareas.ThepopulationstructureandregenerationstatusofwoodyspeciesinbothgrazingexclosuresshowedaninvertedJ-shape,indicatingahealthyregenerationstatus,whereashamperedregenerationwasobservedinopengrazedareas.Theestablishmentofgrazingexclosureshadpositiveeffectsinrestoringwoodyplantdiversityandimprovingvegetationstructureandregenerationpotentialsofdegradedgrazinglands.
简介:Ricesheathblight,causedbyRhizoctoniasolani(Kühn),isanotorioussoil-bornediseaseprevalentinmanyrice-growingregions.AlthoughseveralsporadicstudiesofmycovirusesinR.solaniAG-1IAhavebeenreportedforsinglestrainofR.solaniAG-1IA,therehavebeennoreportsdescribingthedistributionanddiversityofmycovirusesinnaturalpopulations.Inthisstudy,43R.solaniAG-1IAstrainscollectedfromdifferentlocationsinChinawereexaminedforthepresenceofdsRNAelementstoconfirmthepresenceofviralinfections.Electrophoretypesshowedthat16ofthe43fungalstrains(37.2%)containeddsRNAsthatcanbecharacterizedasviruses.Furthermore,thespecies-specificreversetranscriptionPCR(RT-PCR)showeddsRNAbandswithsimilarsizesdonotalwayscontainthesamevirusbutexistasmixedmycoviralinfections.Thus,ourfindingsindicatemycovirusesinfectingR.solaniAG-1IAinChinaarediverse,widespreadanduniversal.
简介:Background:Theimportanceofstructurallydiverseforestsfortheconservationofbiodiversityandprovisionofawiderangeofecosystemserviceshasbeenwidelyrecognised.However,toolstoquantifystructuraldiversityofforestsinanobjectiveandquantitativewayacrossmanyforesttypesandsitesarestillneeded,forexampletosupportbiodiversitymonitoring.Theexistingapproachestoquantifyforeststructuraldiversityarebasedonsmallgeographicalregionsorsingleforesttypes,typicallyusingonlysmalldatasets.Results:HerewedevelopedanindexofstructuraldiversitybasedonNationalForestInventory(NFI)dataofBadenWurttemberg,Germany,astatewith1.3millionhaofdiverseforesttypesindifferentownerships.Basedonaliteraturereview,11aspectsofstructuraldiversitywereidentifiedaprioriascruciallyimportanttodescribestructuraldiversity.Aninitialcomprehensivelistof52variablesderivedfromNationalForestInventory(NFI)datarelatedtostructuraldiversitywasreducedbyapplyingfiveselectioncriteriatoarriveatonevariableforeachaspectofstructuraldiversity.Thesevariablescomprise1)quadraticmeandiameteratbreastheight(DBH),2)standarddeviationofDBH,3)standarddeviationofstandheight,4)numberofdecayclasses,5)bark-diversityindex,6)treeswithDBH>40cm,7)diversityoffloweringandfructification,8)averagemeandiameterofdowneddeadwood,9)meanDBHofstandingdeadwood,10)treespeciesrichnessand11)treespeciesrichnessintheregenerationlayer.Thesevariableswerecombinedintoasimple,additiveindextoquantifythelevelofstructuraldiversity,whichassumesvaluesbetween0and1.Weappliedthisindexinanexemplarywaytobroadforestcategoriesandownershipstoassessitsfeasibilitytoanalysestructuraldiversityinlarge-scaleforestinventories.Conclusions:Theforeststructureindexpresentedherecanbederivedinasimilarwayfromstandardinventoryvariablesformostotherlarge-scaleforestin