Impact of some topographical and soil characteristics on distribution of ecological vegetation groups (Case study: Ranglands of Khud- Niuk basin, Yazd)

To determine the effect of some important environmental factors on distribution of ecologicalvegetation groups، 50 various Land Unit Tract (LUT) were studied. In each LUT، canopy cover and vegetation density، over three line transects were measured in random plots (2 or 16 m2) according to vegetation types. For each sampling unit، one composite soil sample was collected from various depths، and topographical parameters were recorded. Soil properties included: texture، calcium carbonate، pH، EC، soluble ions (Na+، Mg2+ and Ca2+) and SAR were determined. Floristic and environmental data were analyzed by TWINSPAN and CCA methods. The CCA results showed that among the topographic variables، slope and elevation have the most effects on ecological species groups. Vegetation patterns were also significantly affected by soil variables include Na، T. N. V and soil texture.