Relationship between rainfall and annual forage production of the most important shrubs Species in Firuzkuh region

Awareness of annual and monthly production of various rangeland types is essential for efficient management of rangelands. It would be achievement by determining the relationship between plant forage production and climatic variables affecting them especially rainfall which would make easier management. Achieving this goal is facilitated by determining the relationship between the amount of forage production and climatic variables affecting it, especially rainfall, in rangelands. Firuzkuh rangelands were studied to determine the relationship between rainfall and shrub forage production during 2006-2010. For this purpose, the annual and monthly forage production was measured during plant growth season in research exclosure plots by clip and weigh method. Each plant species studied had a specific production during the grazing season in different years. Relationship between forage production and precipitation in periods of winter and spring as well as each month of winter and spring was estimated. Results showed that correlation between the forage production of study species and precipitation in different periods including crop year (0.06 - 0.42), winter and spring (0.01-0.23), March and spring (0.13 -0.35), March and May (0.06 – 0.45), February to June rainfall (0.13 – 0.40), was positive and reached its highest level in June (0.63 -0.94). A significant relationship was found between the forage production of Acantholimon erinaceum, Acanthophyllum spinosum, Astragalus gossypinus, Onobrychis cornuta and Thymus fedtschenkoi and June rainfall.