大学英语四级阅读理解试题及答案(四)十六Treesshouldonlybeprunedwhenthereisagoodandclearreasonfordoingsoand,fortunately,thenumberofsuchreasonsissmall
Pruninginvolvesthecuttingawayofobergrownandunwantedbranches,andtheinexperiencedgardenercanbeencouragedbythethoughtthatmoredamageresultsfromdoingitunnecessarilythanfromleavingthetreetogrowinitsownway
First,pruningmaybedonetomakesurethattreeshaveadesiredshapeorsize
Theobjectmaybetogetatreeoftherightheight,andatthesametimetohelpthegrowthofsmallsidebrancheswhichwillthickenitsappearanceorgiveitaspecialshape
Secondly,pruningmaybedonetomakethetreehealthier
Youmaycutdiseaedordeadwood,orbranchesthatarerubbingagainsteachotherandthuscausewounds
Thehealthofatreemaybeencouragedbyremovingbranchesthatareblockingupthecentreandsopreventingthefreemovementofair
Oneresultofpruningis