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

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


Introduction
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 country few researches with J. polycarpos and J. excelsa have been reported in semi-arid zones (Ghasemi, 1996;Khosrojerdi et al., 2008;Shirzad and Tabari, 2010), but none on Juniperus planted in an arid zone was reported. This investigation is aimed to determine establishment and growth characteristics of J. excelsa seedlings under rainfed/irrigated conditions in a region with 231 mm annual precipitation and 6 months vital dry period.

Materials and methods
This investigation was conducted in southern elevations of Mashhad city located in northeastern Iran (59˚ 27' E, 36˚ 30 N', 1450 m a.s.l.). Based on synoptic station of Mashhad, the mean annual precipitation is 231 mm and the region benefits from a dry climate. The dry season is 6 months, starting from mid-May and lasting in mid-October. In this research 270 three-year old seedlings (1+2) of J. excelsa were planted on a natural soil in the site study. Experiment was made as factorial with randomized completely design, with three irrigation levels including control (rainfed), 20-days interval irrigation and 40-days interval irrigation. Watering was made 15 lit/period in spring and summer. In order to inhibit drought stress the rainfed seedlings were watered once at plantation time. The planting distance was 4 m, planting depth 40-50 cm and mean width of pits 80 cm (Photos 1 and 2). Experiment was done for three years. At the end of each growing season, survival, crown width and total height (with meter, Photo 3) and stem collar base (with digital apparatus) of seedlings were measured and the increments for each period calculated. Soil pH and EC were 7.9 and 0.9 milmos/cm 2 , respectively. Phosphorous and Potassium were 2 and 96 ppm, respectively. Nitrogen, using the Kjeldahl method, was 0.09% and Co 3 Ca and Carbon, using Walkey-Black method, were 0.43 and 32.1, respectively. The soil texture was sandy loam. Analysis data was conducted by SPSS. Quantitative factors as increments of total height, crown width and stem collar base followed determining normality was conducted by Kolmogorow-Smironov test and equality data with Levene test. For comparison of means one-way Anova and Duncan tests were used. Survival was transferred into the normal data by Arc sin (Zar, 1999

Results
The results of the first, second and third years indicated that only in the first year height growth was significantly affected by irrigation treatment (Table 1). The greatest height growth was detected in 20-days interval irrigation and the least in rainfed condition (Table 2). Height growth, stem collar base and survival rate differed with irrigation ( Table 1). Comparison of means in second year revealed that height growth was greater in 20-days interval irrigation than 40-days interval irrigation and control, and no significant difference was found between 40-days interval irrigation and control. Stem collar base was greatest in 20-days interval irrigation and least in rainfed status. Survival rate was highest with seedlings irrigated in intervals of 20 and 40 days. The results of third year showed that increments of stem collar base and crown width were affected by irrigation treatment (Table 1). The greatest and least increments stem collar base were found in 20-days interval irrigation and control, respectively. Crown width increment was greatest in 20-days interval irrigation (Table 2). Year

Discussion
The results of the present investigation at the end of the first, second and third years showed survival rate of seedlings irrigated in intervals of 20 days was 99.3, 74.87 and 74.67%, respectively. In intervals of 40 days it was 75.28, 74.67 and 74.33, respectively in mentioned years. Alrababah et al. (2008) in plantation with J. phoenicea found that watering reduced soil moisture stress and enhanced survival rate. They stated that at the end of the first and second growing season survival was 42% and 32%, respectively. Castro et al. (2005), working with Pinus sylvestris, with irrigation in intervals of 10 days (2 liter/seedling) observed that survival rate was 30% and 22% an the end of years 1 and 2, respectively.

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Likewise, Bjugstad and Ardell (1984) in semi-arid region of Wyoming situated in northeastern of United State found the significant effect of soil moisture on establishment of Prunus americana, Pinus ponderosa and J. scopulorum irrigated as dripping. As a matter of fact, the 5 years finding of mean survival rate of three species was ~ 29%. According to their idea the dry summer, particularly in initial years was a limiting factor for seedling establishment. As a whole, although in the dry regions, survival and growth rate of rainfed planted seedlings is mainly low, under such a condition watering causes increase of these characteristics, but owing to low and irregular precipitation, lacking sufficient water resources and long dry period only drought-tolerant species are able to recompense the rareness of vegetation cover (Boers, 1994;Kozlowski, 1987). However, because of deficient water resources, successful establishment of water-managed plantations would not be secured. Therefore, using the low-moisture demand species or species able to establish at water-lacking status can remove to a great extent criticizes of drought in plantations of such regions (Oliet et al., 2002;Sanchez-Coronado et al., 2007). Rainfed planted J. excelsa seedlings, especially in years 1 and 2, due to deprived rooting and low moisture and nutrient uptake showed higher sensibility to environmental stresses, particularly to drought. So, watering regimes induced enhanced survival. In this respect, it can be stated that because the summer drought in arid zone is a factor affecting growth and establishment of plantations, therefore watering causes decreased the soil moisture stress and increased the establishment and survival rates of seedlings, especially in the primary years (Bjugstad and Ardell, 1984;Garcia, 2001;Maria et al., 2002;Castro et al., 2005). This is while, that in year 3 watering regime did not raise the survival rate. This may me because of appropriate distribution of rooting for soil moisture uptake and also suitable adaptation of seedlings with environmental conditions in the third year after plantation (Tabari et al., 2011). As a matter of fact, the fairly suitable survival of rainfed planted seedlings at the end of years 1, 2 and 3 (69.65, 47.77 and 47.67%) confirms that J. excelsa seedling benefits from the ecological adaptation in this arid area and is able to overcome drought stress following planting, and to establish successfully in the area. In literature, various reports have been cited on adaptability circumstances of Juniperus genus in arid zone and semi-arid zone of the world. According to Bjugstad and Ardell (1984), survival rate of J. phoenicea seedling at the end of the 2 nd year was 32%. In the report of Khosrojerdi et al. (2009, on J. polycarpos) and Ghasemi (1996, on J. excelsa) survival rate of seedlings was 88.61% and 96.3%, respectively. This is while that Khademi et al. (2005) observed the full mortality of J. Virginiana plantation after 10 years. The findings on Pinus genus were different, too. In this respect, it can be paid to some researches including Oliet et al. (2002), who showed that 88.5% of seedlings of P. halepensis grown in a semi-arid area survived at the end of the 1 st growing season. They observed that P. halepensis seedling is successfully able to overcome drought stress after planting and to establish in this area. Generally, native drought-resistant and compatible species with high ecological elasticity are able to a large extent recompense the damages induced by strict environmental variations and water deficiency. Particularly, J. excelsa and J. ashei that with penetration of their roots in soil depths and stone layers access soil moisture and overcome drought stress (Weaver and Jurena, 2008). As a result, plantation with these species in arid and semi-arid areas is of high success.
In this investigation, in different years, with enhanced irrigation in the dry seasons, height growth and stem collar base growth of J. excelsa were increased. Because, the drought stress causes moisture stress in plant and threats its growth, consequently moisture required of plant decreases the drought stress and increases the growth (Matice, 1982;Lantz et al., 1988).

General conclusion
From the results of the present research it can be concluded that at the end of third year the growth characteristics of rainfed planted seedlings did not much differ with those in watering treatments, particularly in watering applied with interval of 40 days. Likewise, establishment of seedlings responded well (about 47%) to rainfed status. As a whole, although under rainfed status survival rate of the J. excelsa seedlings was satisfactory; however, for caution and help in higher assurance of establishment and growth it is better that for plantation development of this species in this arid area and the same ecological regions some irrigations to be applied in the primary years.

Acknowledgment
Many thanks go to the Tarbiat Modares University and the Municipality of Mashhad (Khorasan Razavi Province) for the financial support provided. We also would like to acknowledge Dr. E. Khosrojerdi  The book entitled Water Quality, Soil and Managing Irrigation of Crops comprises three sections, specifically: Reuse Water Quality, Soil and Pollution which comprises five technical chapters, Managing Irrigation of Crops with four, and Examples of Irrigation Systems three technical chapters, all presented by the respective authors in their own fields of expertise. This text should be of interest to those who are interested in the safe reuse of water for irrigation purposes in terms of effluent quality and quality of urban drainage basins, as well as to those who are involved with research into the problems of soils in relation to pollution and health, infiltration and effects of irrigation and managing irrigation systems including basin type of irrigation, as well as the subsurface method of irrigation. The many examples are indeed a semblance of real world irrigation practices of general interest to practitioners, more so when the venues of these projects illustrated cover a fair range of climate environments.