| Poplar is one of the major tree species of fast-growing and high-yielding forest in northern China. It performs an important role in easing the contradiction between supply and demand of timber, protecting security of timber industry, promoting economic development, increasing local income, fixating carbon and generating oxygen. However, the current management of the seedlings of poplar plantation is still relatively extensive. Particularly, the management of water is more extensive. Therefore, it leads to low productivity of seedlings' seedling stage, causing the development of poplar plantation failed in the beginning, which seriously affected and limited poplar plantations'potential of high productivity. Additionally, China is one of the major water-poor countries. A serious shortage of water has been one of the great elements which have been limiting the production of each industry. In order to alleviate the pressure of the water in the existing situation while promoting water management of poplar plantation seedling a more considerable level, this research took different clone seedlings of Populus×euramericana as research materials, focused on establishment of water consumption and water-saving irrigation programs of Populus×euramericana seedlings, by using classical pot-weighting, portable weather stations, pressure gauge etc, monitors dynamically throughout two yeas (2009,2010) to study the water consumption of Populus×euramericana seedlings systematically. The water consumption of different clone seedlings of Populus×euramericana were investigated, also water saving irrigation technologies and optimal irrigation programs which were based on seedlings' growing, water consumption and etc were established, in order to improve the water management of Populus×euramericana during seedling period and promote the sustainable development. The main conclusions are as follows:(1) by using the method of artificial neural network and DPS DATA PROCESSING SYSTEM combined with the meteorological data of air temperature, relative air humidity, solar radiation, wind speed, soil water content and dew point temperature as the input variable, the author established the artificial neural network system to forecast the seedling water consumption of P.×euramericana cv. "74/76", and through the experiments it has been examined that three neural network system models can be applied in forecasting water consumption of seedlings, and the average relative error of Back Propagation (BP) neural network predication model was 0.04, the projection pursuit regression (PPR) neural network predication model was 0.03, the multiple stepwise regression anatomic model was 0.10, moreover, the latter two ones had good stability, while that of BP neural network predication model was poor. Therefore, we propose that PPR neural network model can be used in prediction of seedling water consumption. Furthermore, the maximum relative error of PPR neural network predication model was 0.073, the minimum relative error was 0.002. The neural network model is superior to the former linear model that the neural network model performs a higher forecasting accuracy with relatively shorter time consumption in training.(2) According to the physical and Morphological characters of different clones of Populus×euramericana under different soil moisture content, the optimal soil moisture content for seedlings was confirmed to be 80%(60%?80%;18.8%) of the field capacity.(3) The annual water consumption in different clones of Populus xeuramericana seedlings showed the same water consumption rule. Water consumption was increased with soil water content increasing, which was 100%>80%>60%. To the optimal soil moisture content, annual water consumption of Populus×euramericana cv. "74/76" was minimum, at 146.83kg·m-2; the maximum was Populus euramericana 'Lingfeng 4', at 264.25kg·m-2. The water consumptions in different clones had extremely significant difference (P<0.01).(4) Water Use Efficiency (WUE) in different clones of Populus×euramericana seedlings was increased with soil moisture content decreasing, which was 60%>80%>100%.under optimal soil moisture content, Populus×euramericana cv. "74/76" showed the highest average WUE (2.71±0.52)?molCO2·mmol-1H2O. the lowest was Populus euramericana 'Lingfeng 3', at 264.25kg·m-2. The water consumptions in different clones had extremely significant difference (P<0.01).(5) Differences of water consumption of seedlings among seasons were analyzed under optimal soil moisture content. Populus×euramericana cv. "74/76", Populus euramericana 'Lingfeng 1' and Populus euramericana 'Lingfeng 4' belong to summer and autumn-water consumption type. Populus deltoides CL. 'Imperial' belongs to summer-water consumption type. Populus euramericana 'Lingfeng 3' belongs to average water consumption type. Type of water consumption could change when the same clones that grow under different soil water content was also presented. Populus euramericana 'Lingfeng 3' belongs to autumn water consumption type under 60% of field capacity, belongs to average water consumption type under 80% of field capacity, belongs to summer water consumption type under 100% of field capacity.(6) The sequence of correlation between transpiration rate and environmental factors is solar radiation, relative humidity, temperature, soil water potential, and solar radiation is the most correlated (P<0.01).(7) Multivariate Linear Regression model between transpiration rate and environmental factors reached significant level (P<0.05).under optimal soil water content, the R2 of different clones were as followed:Populus×euramericana cv. "74/76" was 0.826?Populus deltoides CL.'Imperial' was 0.837?Populus euramericana 'Lingfeng 1' was 0.902?Populus euramericana 'Lingfeng 3' was 0.862, Populus euramericana 'Lingfeng 4' was 0.815. Measured data of environmental factor were taken into model for prediction, relative errors were as followed: Populus×euramericana cv. "74/76" was 18.18%, Populus deltoides CL. 'Imperial' was 11.43%, Populus euramericana 'Lingfeng 1' was 15.18%, Populus euramericana 'Lingfeng 3' was 5.93%, Populus euramericana 'Lingfeng 4' was 10.90%. Forecast error in the model is acceptable (<20%), and forecasting model is accurate.(8) Based on the water consumption discipline of potted Populus×euramericana seedlings, combined with the situation of soil evapotranspiration and rainfall capacity, Water-saving Irrigation systems were determined preliminarily for different clones of Populus×euramericana under optimum soil water content. The irrigation water requirement of five clones of Populus×euramericana was divided into two groups, Populus×euramericana cv. "74/76" and Populus euramericana 'Lingfeng 3' belonged to one group, their irrigation water requirement was relatively less; Populus deltoides CL.'Imperial', Populus euramericana 'Lingfeng 1' and Populus euramericana 'Lingfeng 4' belonged to another one, their irrigation water requirement was relatively more. In the whole growth season, the irrigation water requirement of Populus×euramericana cv. "74/76" was 54.53 kg, and according to weather condition the irrigation water requirement was divided into some times' irrigation, about 45 times, irrigation water requirement of Populus euramericana 'Lingfeng 3' was 56.90 kg, about 54 times; irrigation water requirement of Populus deltoides CL.'Imperial', Populus euramericana 'Lingfeng 1' and Populus euramericana 'Lingfeng 4' were 70.47kg,72.17kg,78.47kg, averagely about 84 times. |
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