Growth Characteristics of Rainfed/Irrigated Juniperus excelsa Planted in an Arid Area at North-Eastern Iran

Abstract

Many dry regions of the world due to shortage enough water resources are lacking vegetation cover. This is while that the severe deforestations happened during short time has decreased their surface area in recent decades. Using the drought-tolerant species for rehabilitation of these regions and compensation of water deficit is promising (Tabari et al., 2011) Although, in dry regions the survival rate of planted seedlings managed as rainfed is low and watering causes enhanced survival and growth (Koroori and Khoshnevis, 2000; Lichter, 2000; Shirzad, 2009), because of low and irregular rainfall, long dry period, insufficient water resources, only drought tolerant tree species are able to recompense the scarceness of vegetation cover (Boers, 1994; Kozlowski, 1987). These species owing to the high capacity of water storage at stem and branch, and the good rooting in soil are able to well bear the drought status and to overcome the drought stress (Oliet et al., 2002; Tabari et al., 2011). Since the vast regions of world have dry climate, strategies for perfect use of the water resources and the drought-resistant species, which are able to highly benefit from the soil moisture, can be the main targets of plantation in such regions (Oliet et al., 2002; Sanchez-Coronado et al., 2007). Juniperus excelsa is distributed in vast areas of Irano-Touranian growing regions (Zare, 2001). It tolerates high dryness and coldness and is able to restore deforested areas in mountain arid and semi-arid zones (Hampe and Petit, 2010). Of course, except Juniperus excelsa, other conifers have been also investigated for rehabilitation of such lands. Baquedano and Castill (2006), Oliet et al. (2002) and Castro et al. (2005) state that Pinus halepesis seedling is successfully able to overcome drought stress and it is a good species for plantation in arid and semi-arid areas. Khosrojerdi et al. (2008) and Ghasemi (1996) in the order put forward J. excelsa and J. polycarpos for plantation in semi-arid regions of Iran. Likewise, plantation with J. phoenicea in Mediterranean semi-arid regions of Jordan, and with J. scopulorum in semi-arid regions of northeastern United State has been reported by Alrababah et al. (2008) and Bjugstad and Ardell (1984), respectively. Because water resources in arid and semi-arid regions of Iran is a serious obstacle for plantation development, so researches to apply suitable methods with the drought-tolerant species is imperative. Thus, the researches necessary in order to assessing the primary establishment of J. excelsa in arid zones of the country is unavoidable. Although, in the