the study area includes a longitudinal profile extending from southern slop of Alborz to Haj Ali Gholi Karir of Semnan province.the result show that elevation,precipitaion and slope rate as the first principal component and precentage of sand, loam and ESP as the second principal componente explain 39% and 20% of vegetation cover variation respectively.The result show that by using P.C.A alalysis we can able to determineecologycal similarity among plant associationand classified them in similar groups as well
