The Relationships between Different Plant Communities and Environmental Factors in Gonbad Watershed, Hamadan

The knowledge of rangeland vegetation types and factors influencing on their establishment and stability is essential for sustainable management and regeneration of rangeland areas. With this aim, Gonbad watershed, due to different vegetation types, environmental conditions and grazing managements was studied. The watershed was stratified to homogenous units based on morphology of vegetation types and environmental factors. Land properties, total canopy and canopy of the main five vegetation forms (annual grasses, perennial grasses, annual forbs, perennial forbs, and shrubs) were determined in 3 to 4 plots (1 x 1 m2) in each unit; plant and surface soil were sampled. Using TWINSPAN method, Silen sp., Centaura virgate, Astragalus verus and Cousinia bijarensis were identified as indicator species. DCA analysis subdivided the watershed into six ecological groups based on indicator plant species, production of perennial grasses and environmental factors, such as percent of sand and clay, and slope aspect. Based on the analysis of indicator species Asteragalus gossypinus (p= 0.001), Taeniatherum crinitum (p= 0.002) and Heteranthelium piliferum (p= 0.007) classified the vegetation cover into three main groups. Silen sp., Astragalus gossypinus, Centaurea virgat, Artemisa siberi, and Festuca ovina represent mountainous steppe and semi-steppe ecological environments. These deep rooting species are resistant to dry conditions. Therefore, ecological