Water requirement of some forest species used for afforestation in arid and semi-arid regions

Due to the lack of attention to ecological needs of forest species in arid and semi-arid areas especially the water requirement or evapotranspiration, the afforestation projects have no desirable sustainability and achievement of the goals is not well obtained. As the age of the plants increases, their water requirement increases and in many cases, the competition between the trees to provide the moisture requirements is intensifies. Available studies indicate that most forest species in these areas have lower evapotranspiration (ETc) as compared with potential evapotranspiration (ETp) and have little crop coefficients (Kc). These species can deal with drought stress through various morphological, physiological, biochemical, and ecophysiological mechanisms and or use available water resources to improve the production function and water use efficiency. To measure the daily evapotranspiration and calculate crop coefficient of these plants, direct or lysimetric methods and indirect or computational methods are used. In this paper, the daily water requirement of Haloxyllon aphyllum, Tamarix aphylla, Atriplex sp., Calligonum sp., Poulus euphratica, Elaeagnus angustifolia and several species of eucalyptus (Eucalyptus camaldulensis, E. microtheca, E. sarjentii, E. leucoxylon and E. floktoya) was investigated. Among the species mentioned, Eucalyptus camaldulensis (10 mm) and Calligonum (2.2 mm) had the highest and lowest water requirement.