Study On Water Consumption Of Seedlings For Forestation In Semi-arid Region On Loess Plateaus

Aiming to solve the contradiction between demand for the extension of forest vegetation and the limited water supply in arid and semi-arid area and based on the theory of soil-plant-atmosphere continuum, the dissertation chose the main afforestation tree species Patycladus orientalis ,Pinus tabulaeformis ,Robinia pseudoacacia ,Populus pekinensis,Ulmus macrocarpa and Prunus armeniaca on Loess Plateaus in Growing Seasons of 2005, utilized advanced apparatus, equipments and various approaches, systematically analyzed of relationship between wood production with water consumption and studied the ecophysiological characteristics of tree transpiration and water consumption. Target of the researches is to meet the need in choice of tree species with drought-tolerance and lower water consumption, higher survival rates, and afforestation and reconstruction of forest vegetation in the arid and semi-arid areas of China.Main research results are as follows:Under the condition of free soil water stress, the diurnal changes of transpiration rate and stomatal conductance of eight main afforestation tree species display a signal-peak curve. The transpiration rate of coniferous trees was the lowest, whilst the broad leaved trees were the highest, and the shrub species fell between coniferous species and broad leaved species. With the increase of soil water content ,the transpiration rate, stomatal conductance and water use efficiency increase under the different soil water content.The water consumption proportion of different seedlings was in the same trend, but the factual data was very different. Populus alba had the highest water consumption, Patycladus orientalis and Pinus tabulaeformis were the lower water consumption plants, Robinia pseudoacacia, Prunus armeniaca, Amorpha fruticosa were in the middle. The water consumption rates of coniferous species were less obviously than that of the broadleaf tree species. Also, The water consumption rates of broadleaf tree species, like as Populus alba,Robinia pseudoacacia were 5 to 10 times as much as that of Patycladus orientalis and Pinus tabulaeformis. While the water consumption rates of shrubbery species like as Amorpha fruticos and Prunus armeniaca were 2 to 3 times as much as that of Patycladus orientalis and Pinus tabulaeformis. The water consumption of trees was relevant to their water consumption rate and leaf area, accordingly, it is very important to select tree species, which has lower water consumption and drought tolerance, and set reasonable stand density in recovery and reconstruction of forest vegetation.The soil water content had obvious affect on water consumption and biomass. The water consumption and biomass of six tree species had the same proportion, which was the highest in...