简介:以便在不同agro生态的地区在农田上测量灰尘的滋养的输入,非洲西部十二月至三月所吹的寒冷干燥北风灰尘被地席在在20022006之间的迦纳与塑料稻草取样。由在迦纳的非洲西部十二月至三月所吹的寒冷干燥北风灰尘的全部的营养素的输入每非洲西部十二月至三月所吹的寒冷干燥北风时期是大约12kgCa哈1,0.52kgK哈1,0.51.5kgMg哈1和不到0.5kgP哈1。与由降水的营养素的年度输入相比,灰尘Ca,Mg和K,但是近似占了10%或少些P的20%40%。,由灰尘的营养素的输入在区域为有植被的区域仅仅是有效的与没有或稀少的植被,由于风侵蚀并且在此,营养素的损失可能是的土壤的损失重要。在有赤裸、生长的地的农田区域,似乎是营养素的内部再分配和从在区域(远程的搬运灰尘)外面的营养素的并非网获得。当Ca,Mg和K的另外的三营养素的输入是那么低的他们必须被认为不足道时,由灰尘的P的输入可能具有在传统的变耕作系统的某重要性。在有粪肥和化肥的巨大的输入的集中的农业系统,由灰尘的滋养的输入是不足道的并且能被忽视。
简介:Growthofcommercialforestryishighlydependentontheavailabilityoffast-growingplantingmaterials.Consequently,theefficientutilizationoffastgrowingplantationscangreatlyimpactproductivity.Theobjectivesofthisstudyweretoevaluatevariationsinthegrowthpotentialoftwoclonesandtoestimatetheaveragestemradialgrowthadvantageofafast-growingcloneusingdataobtainedfromSappilandholdingsineasternSouthAfricaandamixedmodellingapproachthatpermitstheincorporationofcovariancestructureintothestatisticalmodel.Duringthefirst2yearsofgrowth,thestemradiusofninetreeseachoftwocloneswasmeasuredusingdendrometerattachedtothetree.Asecond-degreefractionalpolynomialmodelwaschosentoshowthefunctionalrelationshipbetweenstemradiusandtreeage.Growthofthetwohybridclonesdifferedsignificantly.TheEucalyptusgrandis9EucalyptusurophyllaclonegrewfasterthantheE.grandis9camaldulensisclone,indicatingbettergeneticpotentialforrapidgrowthandyield.Thisstudycanbeconsideredasstartingpointtofurthercomparethepotentialforrapidgrowthofseveralhybridclonesusingthelongitudinaldatamodellingapproach.
简介:很少对在差的oxisol上的为非洲(NERICA)的在新瑞斯的生产和质量上的在植被盖子下面的直接播种的影响被知道。在这研究,二个NERICA变化(NERICA3和NERICA8)与很低的滋养的内容在热带oxisol土壤下面被种。四个耕作系统在完全使随机化的块设计被使用,包括耕作(控制),有死了的植被盖子(DVC)的unplowed土壤,有实时植被盖子(LVC)的unplowed土壤和unplowed与混合植被盖子(MVC)玷污。DVC显著地改进了NERICA的指数的生长。NERICA3是更多生产(2.16-3.05?t/hm2)与NERICA8相比(0.71-1.21?t/hm2)。耕作系统改进了NERICA的营养的质量。在DVC和MVC下面的NERICA3的全部的蛋白质内容分别地比控制高是84.8%和75.0%。全部的可溶的糖类在LVC下面NERICA8满足,MVC分别地比控制高是73.2%和57.3%。这些结果建议了象与植被盖子系统的在unplowed土壤上的直接播种一样的那条保守途径能在sub-Saharan非洲在差的oxisol土壤下面改进rainfedNERICA和他们的持续生产的营养的质量。
简介:Background:Tropicaldryforestscoverlessthan13%oftheworld'stropicalforestsandtheirareaandbiodiversityaredeclining.InsouthernAfrica,themajorthreatisincreasingpopulationpressure,whiledroughtcausedbyclimatechangeisapotentialthreatinthedriertransitionzonestoshrubland.Monitoringclimatechangeimpactsinthesetransitionzonesisdifficultasthereisinadequateinformationonforestcompositiontoallowdisentanglementfromotherenvironmentaldrivers.Methods:Thisstudycombinedhistoricalandmodernforestinventoriescoveringanareaof21,000km~2inatransitionzoneinNamibiaandAngolatodistinguishlatesuccessiontreecommunities,tounderstandtheirdependenceonsitefactors,andtodetecttrendsintheforestcompositionoverthelast40years.Results:Thewoodlandsweredominatedbysixtreespeciesthatrepresented84%ofthetotalbasalareaandcanbereferredtoasBaikiaea-Pterocarpuswoodlands.Aboostedregressiontreeanalysisrevealedthatlatesuccessiontreecommunitiesareprimarilydeterminedbyclimateandtopography.TheSchinziophytonrautaneniiandBaikiaeaplurijugacommunitiesarecommononslightlyinclinedduneorvalleyslopesandhadthehighestbasalarea(5.5-6.2m~2ha~(-1)).TheBurkeaafricana-GuibourtiacoleospermaandPterocarpusangolensis-Dialiumenglerianumcommunitiesaretypicalforthesandyplateauxandhaveahigherproportionofsmallerstemscausedbyahigherfirefrequency.AdecreaseinoverallbasalareaoratrendofincreasingdominationbythemoredroughtandcoldresilientB.africanacommunitywasnotconfirmedbythehistoricaldata,butthereweresignificantdecreasesinbasalareaforOchnapulchraandthevaluablefruittreeD.englerianum.Conclusions:Theslopecommunitiesaremoreshelteredfromfire,frostanddroughtbutaremoresusceptibletohumanexpansion.ThecommunitywiththeimportanttimbertreeP.angolensiscanbestwithstandhighfirefrequencybutshowssignsofahighervulnerabilitytoclimatechange.Conse
简介:Background:Prosopisspecieshavebeenintroducedtomanyareasoutsidetheirnativerangetoprovidebenefitstolocalcommunities.SeveralProsopisspeciesandtheirhybrids(hereafter"mesquite")have,however,becomenaturalisedandinvasiveandnowgeneratesubstantialcosts.Managementoptionsarelimitedbecauseofthecomplexconflictsofinterestregardingbenefitsandcosts.Managementpoliciesandstrategiesmusttakeaccountofsuchconflicts,butfurtherinsightsareneededonthedimensionsofusesandimpactsbeforesuchinformationcanbeusefullyapplied.CurrentpolicyinSouthAfricaallowsforthegrowthanduseofmesquiteinoneprovince,butnotinotherswhereitscontrolismandatory.Wereportonastudytoquantifythedirectuseandperceptionsofnon-timberforestproducts(NTFPs)frommesquiteandnativetreesinSouthAfrica.Methods:Semi-structureshouseholdinterviewswereconductedwithvariousstakeholdergroupstoidentifywhattreeproductsareused,toascertainamountsusedaswellastogaugeperceptionsofnaturalresourceusebetweendifferenttreespeciesanduseovertime.Results:Thedirecthouseholdusevalueofnativetreeswashigherthanthatofmesquite,andlocalstakeholdersattachedgreatervaluetoproductsfromnativetreesthanfrommesquite.Therefore,nativetreesareandwillstillbepreferentiallyharvested,andmesquiteisunlikelytoofferprotectiontonativespeciesbyprovidinganalternativesourceofproducts.Mesquitepodsdo,however,providevaluableadditionalresources(fodderandmedicinalproducts).Theuseofbothnativetreesandmesquiteisdecreasingastheincomesofpoorerhouseholdsriseandasalternativeenergysourcesbecomeavailable.Thebenefitsandrelianceonmesquitearenotashighaspreviouslyassumedandtheimpactsfrommesquiteinvasionscreatelargeproblemsforlocalcommunities.Conclusion:Thisstudyprovidesfurtherevidencethattheimpactsofmesquiteexceedthebenefits,lendingsupportforapolicytoreducenegat
简介:Bt玉米叶垃圾的化学作文上的基因修正的非计划中的效果可以在它的分解上有影响。在在南非的很农业的系统,玉米垃圾是任何一个留在土壤表面上或在耕种期间合并了到土壤。用三个玉米混血儿(DKC80-12B,DKC80-10和DKC6-125)的叶垃圾,一个litterbag实验在堡垒兔研究农场的大学被执行,南非,为了在玉米叶的分解上决定基因修正的效果,乱丢东西什么时候在在7月和11月之间的地条件下面留在土壤表面上,正常休闲时期,在2008。另一个litterbag实验在堡垒兔研究农场的大学被进行,使用南非遗传上与cry1Ab修改了的二个玉米混血儿的叶垃圾并且Zanyokwe灌溉计划,基因(MON810),DKC75-15B和PAN6Q-308B,和他们的相应近的isolines,CRN3505和PAN6Q-121。在崽的Cry1Ab蛋白质的降级,适用表面、合并土壤,也被调查。当在表面上适用时并且当合并了到土壤时,Bt玉米垃圾的分解类似于non-Bt玉米垃圾的。合并土壤的垃圾,以及它的Cry1Ab蛋白质,比在表面上适用的快分解了。叶崽C:PAN6Q-308B和PAN6Q-121的N比率在整个学习是类似的,而那些在一个12星期的时期期间由类似的数量DKC75-15B和CRN3505衰退了。这些调查结果建议与MON810事件,Bt玉米的叶垃圾的那分解没被玉米影响基因修正,并且Cry1Ab蛋白质不管崽是否在土壤表面上被使用或合并了到土壤在冬季休闲期间和植物叶垃圾垮掉。