Pasture improvement and management in arid zones of Iran

Abstract

Iran exhibits extreme variation in climate, physiography and vegetation, with the bulk of the country occupied by steppe and desert. These are characterized by shrub or herbaceous formations, the density of which are largely dependent upon the amount of rainfall. Rangelands of Iran have been grazed by livestock for many centuries. There is convincing evidence that most of the mountain slopes and uplands were covered by trees and grasses as recently as the 16th century. The main ecological factors acting on the vegetation of the steppic zone are climatic, edaphic, topographic and biotic. Many features of the climate make plant growth difficult. These include low precipitation, intense solar radiation, high evaporation during the summer months and low winter temperatures. Over most of the zone the rains are often violent and occur at long intervals; for a given amount of precipitation, the number of rainy days is small. Much of the water streams down the slopes and does not benefit the local vegetation. The Forest and Range Organization of Iran has applied different improvement practices on the rangelands, depending on local climatic and edaphic conditions. Depleted rangeland areas where the precipitation was over 300 mm and the soils satisfactory have been reseeded with grasses and forbs; over 50,000 ha have now been successfully revegetated. Water conservation measures, such as contour furrows and pits, were used for conserving moisture to increase production. In the steppic zone, over 50,000 ha have now been improved by planting shrubs. Rangelands that had been depleted due to mismanagement, but still had some desirable vegetation cover, were protected for a minimum of 5 years. Areas where the application of improvement practices was neither economically feasible nor practical were protected for a minimum of 10 years. Sand dune stabilization is of extreme importance to Iran. Active dunes occupy about 5,000,000 ha of the land area. To stabilize the sand dunes, the first stage is to stop movement of the sand particles, either by construction of palisades using reeds, shrubs and herbs or by petroleum mulching where the speed of the wind is such that palisades are ineffective. Once dune movement is stopped, adapted species are established to complete stabilization. Over 4,000,000 ha of sand dunes have now been stabilized. In an extensive afforestation programme, some 30,000 ha have been planted with conifers, poplars and hard wood species during the past 17 years.