Document Type : Original Article
1 Department of Forestry and Forest Economics Faculty of Natural Resources, University of Tehran, Karaj, Iran
2 Department of Water Engineering, Faculty of Agricultural Engineering and Technology, University of Tehran, Karaj, Iran
3 Department of Public Administration, Faculty of Human Science, Islamic Azad University, Firooz Kooh Branch, Firooz Kooh, Iran
Introduction: One of the main limitations in arid and semi-arid regions is the allocation of water resources for green space development. Since water and drought stresses along with an incorrect selection of species are the main factors that reduce seedling survival in the afforestation stages in arid and semi-arid regions, the aim of the current study is to investigate the morphological characteristics of Ash, Mullberry and Ash leaved maple seedlings in the greenhouse and the field under different water stress in Robat Karim town.
Material and methods: Robat Karim is one of the towns of Tehran Province with an area of 275 square kilometers. To study the effect of water stress on morphological characteristics of seedlings species (three species) in two environment (greenhouse and field), 20 seedlings (120 seedlings in total) were planted in greenhouses and fields and in three water stress levels (two, four and six days after reaching MAD point) were tested in randomized complete block design with five replications. The saplings that reached the MAD point were not irrigated immediately and were subjected to three drought stresses two, four and six days after reaching the MAD point. Then the quantitative appearance characteristics of seedlings include parameters of leaf numbers, leaf size, seedlings height, and collar diameter, dry leaf weight, stem dry weight along with two qualitative characteristics of seedlings, which are leaf freshness and seedling health, were measured.
Results and discussion: The results showed that the number of MAD period times in the greenhouse for Fraxinus rotundifolia Mill. species was 29, Acer negundo 28 and Morus alba 32 and in the field for Fraxinus rotundifolia Mill. species was 20, Acer negundo 20, and Morus alba 17 period times. Generally, in all three studied species, in May, as the first month of the research, the seedlings were in very good condition. In other months, after being under different water stress (two, four and six days), the number of leaves and leaf size always decreased over time. In the case of Ash leaved maple, the number of leaves in the greenhouse area in August was zero (absolute defoliation).
Conclusion: Generally, by increasing water stress, leaf number, leaf size, dry leaf weight, dry stem weight, leaf freshness, and health of the saplings were reduced. It seems that six days after reaching MAD point is the suitable time to irrigate the saplings according to their morphological characteristics. Considering the appearance of seedlings during irrigation, it helps to use water efficiently, prevent over-irrigation and under-irrigation of seedlings and save the relevant costs.