Study On Characteristics Of Water Consumption By Transpiration Of Zenia Insignis

China is plagued by a serious shortage of water resources, but forest trees consume a large amount of water resources each year. For a long time, due to low awareness of the water consumption law for plants, irrigation management is blind which causes huge waste of water resources. By taking Zenia insignis as its object, selecting reasonable planting density and improving utilization efficiency of water resources as its goal, this thesis focuses on tests of young plantation in different densities, potted seedlings at diffent ages and environmental factors. Based on these research results, the author concludes the fluctuation law of water consumption for Zenia insignis, makes a water consumption comparison among the trees of different densities and ages, builds up a relationship model between water consumption and dominant environmental factors and makes a scaling up.The following is the main results obtained in this research:It is the primary purpose of this work to provide information about the water consumption in species of different densities and ages. Field experiment:transpiration rate showed 3*3＞1.5*1.5＞1*0.3,utilization efficiency of water from high to low is 1.5*1.5＞1*0.3＞3*3;Pot experiment:daily water consumption showed current-year seedlings> annual stubble seedlings, utilization efficiency of water showed current-year seedlings>annual stubble seedlings.The influence of environmental factors on transpiration is analyzed. With sufficient water supply, stomatal conductance and sun radiation have a strong influence on transpiration rate of all kinds of species, while relative humidity and temperature have relatively weak influence on transpiration rate.Water consumption of all kinds of seedlings in different months was discovered. With sufficient water supply, the water consumption of current-year seedlings from high to low is June>August>November> October, annual stubble seedlings is August>June>November>October; Under water controlling, the water consumption of two seedlings showed June＞August＞November＞October.Five optimal models of transpiration rate and environmental factors in young plantation and pot experiment are created.According to physiological and outside characteristics of all kinds of trees with different water supply, during tests soil water-storage capacity of current-year seedlings is 17.12%(water potential-0.265 MPa), annual stubble seedlings is 22.30%(water potential-0.096 MPa);effective threshold value of soil moisture of current-year seedlings is 14.80%(water potential-0.331 MPa), annual stubble seedlings is 16.79%(water potential-0.325 MPa);threshold value of current-year seedlings is 8.39%(water potential -0.449 MPa), annual stubble seedlings is 10.41%(water potential-1.343 MPa); and if soil moisture of current-year seedlings is less than 7.83%(water potential -0.456 MPa), annual stubble seedlings is less than 5.95%(water potential -3.619 MPa),plants will languish permanently. The soil water supply is divided into three grades:sufficient soil water, slight water deficiency,moderate scarcity of water.During half a year observation, some advanced instruments such as Li-6400 Portable Photosynthesis System and SEC are used. In addition, there are 3～5 parallel tests for each test project integrating with long time-span observation and multitemporal observation in order to obtain precise data. In this thesis, Zenia insignis is taken as its object.It is the first time to study the characteristics of water consumption by transpiration of Zenia insigni of different ages and densities, combine the water consumption with the planting density selection and reasonable irrigation. The highlights of this thesis lie in the selection of research object, research system and integrating theory with practice.