从生态学论“三北”防护林在宁夏的规划原则

？NingxiaHuiAutonomousRegionissituatedin30;14′–30;14′and30;33′–30;39′.Thoughitsarea.Isonly67000km2,ithasmanyvariousecosystemcategories.Thevegetationisthecoreoftheecosystem,soitisveryimportanttoresearch.ThevegetationinNingxiaisthecombinationofmanyvariousvegetationtypeswhichhavecertainegularityofecogeographicaldistribution.ThezonalvegetationtypesinNingxiaarcthesemi-desert,thesteppeandthemeadow-steppefromnorthtosouth.AndtherearethespectrumsoftheverticalbeltsofthevegetationinHelanmountainandLupanmountain.Therearealsomanyintrazonalvegetationtypes—thesaline-meadow,thegrass-swamp,thesaltvegetation,etc.Everyvegetationtypeexistsmanyvariousplantcommunities.Andeachvegetationtypeorplantcommunitycanreflectthecomprehensiveecologicalfactors.Accordingtotheregularity,wemayputforwardaprincipleofplanofthe"Sanbei’(northeast,northandnorthwestChina)shelter-forestinNingxia:l.ItissuitabletoestablishthescrubbeltsinNingxia.Inthesemi-desert,thesteppe,themeadow-steppeandthegrass-tuft,thesoilerosionontheslopesmaybecontroledbythescrubbeltsfollowingcontour-lineandthewind-sand-harmontheplateauplainmaybepreventedbythescrubnetworks;2.Toplanttheshrubs,thesemi-shrubsandthetherophytesissuitableforfixingthesanddrift;3.Itisn’tdifficulttoplanttheshelter-forestintheirrigationfarmland.Butitisveryimportanttochoosethetreespeciesadaptingvarioussoil;4.Alloftheforestandthescrubinthemountainsmustbeclosedandtended.Themixed-forestmaybeexpandedonthemeadowslope.