بررسي آثار عوامل محيطي بر استقرار و گسترش گياهان مرتعي با استفاده از آناليز چندمتغيره

Multivariate Analysis of Environmental Factors Effects on Establishment and Expansion of Rangeland Plants

This study was carried out to investigate the relationship between environmental factors (including climate, soil and topography) and establishment and expansion of rangeland plant types on north and north east areas of Golestan province. On the basis of fieldwork, 23 ruling vegetation types were identified and the effective environmental factors were investigated. On each plant type, the soil profile was dug and the soil samples were taken from 0-30 cm and 30-60 cm depth. The soil factors that were analysed comprised of texture, SP, EC, pH, PSP%, CEC, N, K and P. For analysis of soil factors, the USDA standard method was used. Such topography factors as elevation, aspect and slope and also rainfall and the critical water table depth were calculated for each vegetation type. Using Kovda formula, the critical water table depth was calculated. The multivariate analysis was used to determine relationship between vegetation types and environmental factors. A matrix of vegetation types and environmental characteristics was prepared, and the ordination of vegetation and environmental factors were done by the Principal Component Analysis (PCA) using PC-ORD software. The results show that the environmental factors affected vegetation establishment and expansion. The most important factors that influenced vegetation type s separation were as follow water table depth, aspect and soil salinity. The multivariate analysis explains the effects of complicated environmental factors on the plants by means of a simpler way, introducing one or more important factors.