A Survey of the Effect of the Physiographic Conditions on Vegetative Changes of Rangelands in Haraz Watershed

The recognition of relationship between vegetation and physiographic factors can be useful and effective in estimating the kind and amount of vegetation for the management of various ecological ecosystems of rangelands. For this purpose, the present research deals with studying the effects of physiographic factors on the various vegetative changes of Lasem watershed rangelands. The samples were randomly selected from the vegetatives after the identification of plant types and the determination of the size and number of them. Then, the databases, including the slope, aspect, altitude, and lithology in the area of Arc GIS 9.2 were prepared, and by overlaying them, and after the field controlling, the needed data in each plant type were determined. Finally, the correlation between the physiographic factors with plant types and the means of the properties of the groups were computed with the SNK test. Also, the plant communities were ranked and classified with DCA, CCA and Canoco software, The results showed that shrubs had more correlation with altitude and aspect than grasses, but none of them had any significant relation with the slope. Also, the overgrazing of livestocks decreased the amount of this correlation.