| Water shortage in most parts of Beijing and the surrounding was focused as a hot problem, but the cultivation and planting seedlings consumed a lot of water in these places. Based on the classical weighing method and using 1-0 and 1-1 seedlings of Quercus Variabilis as experimental material, a detailed calculation and comparison of records about water requirement in two ages of seedlings throughout the growing period had been done in this paper. The best water gradient was chosen as a basis for the formulation of water-saving irrigation system in these two ages of seedlings. Meanwhile, a correlation model between water demand and growth index in different moisture gradient and main meteorological factors had been established. All these provided a theoretical basis for precision cultivation and water-saving irrigation on seedlings of Quercus Variabilis in the future.The main results of this paper:Seasonal changes and diurnal variation of water in seedlings of different moisture gradient was defined:in the setting of 90%,70%,60%,50% and 40% of the five water gradients, each gradient of water utilization went through a overall law which started rising from 7:00-8:00 in the morning and began to decline at 14:00. Meanwhile, from the start of the trial in May to the end of the trial in October, water utilization had also experienced a downward trend after rising. In May, the water utilization of different gradients of seedlings was no significant difference. As the trial processed, water utilization of seedlings and different moisture gradients were positively correlated, and the difference of monthly water utilization in different moisture gradient was maximum in July, respectively:△1-0(90%)= 136.46ml/plant·month,△1-0(70%)= 96.73ml/plant·month,△1-0 (60%)= 50.3ml/plant·month,△1-0(50%)= 11.91ml/plant·month,△1-0(40%)= 8.9ml/plant·month;△1-1 (90%)= 312.21 ml/plant·month,△1-1 (70%)= 218.13 ml/plant·month,△1-1(60%)= 157.13 ml/plant·month,△1-1 (50%)= 60.87 ml/plant·month,△1-1 (40%)= 35.12 ml/plant-month. In this paper, the indicators of seedlings growth in different water gradient were also given specific measurement, and a corresponding analysis of variance had been made.60% water gradient, which was the best moisture gradient suitable for 1-0 and 1-1 seedlings, had been selected. Throughout the growing season, the water utilization of 60% water gradient in different seedling age, compared with the water gradient of 70%, declined 26.8% and 23.4% respectively, both of which had achieved the basic requirements of water saving part in task book (saving 20% or above). At the same time, after researching the difference of water utilization in different water gradients, a relational model of water utilization of different moisture gradient and indicators of growth including height (H), diameter (D) and biomass (B) was established.Water Stress on chlorophyll and MDA content and antioxidant enzymes (SOD, POD, CAT) activity of Quercus Variabilis Seedlings was also very significant. With the decrease of moisture gradient, both of the content of chlorophyll a and b declined, and the change in chlorophyll was larger than chlorophyll b. The activity of various antioxidant enzymes and MDA was contrary to the content of chlorophyll, and the lower the moisture gradient, the greater the activity of various enzymes was. This indicated that seedlings produce a resistance to water stress response in order to maintain the mechanism of water requirements in plant.Meanwhile, the real-time of main meteorological factors was observed, and established a correlation model between the result and water utilization. However, there were still some interactions among the meteorological factors, and the test was carried out in the rain-shelter, so the correlation model between the meteorological factors and seedling water utilization can only be general analysis of the correlation between water and climate, not the basis for determining the irrigation system.Finally, the moisture gradient of 60% as the best gradient of seedling irrigation system had been established, the single total irrigation of 1-0 and 1-1 Quercus Variabilis seedlings per year were:7.332×103 mL/plant and 13.526×103 mL/plant, and were irrigated in different scale by month and growth cycles.Based on both correlation model of water utilization and growth indicator of seedlings and water utilization, the irrigation system was established, a trial and theoretical basis was provided for water saving of seedlings and precise cultivation of saplings on Quercus Variabilis.
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