The Transpiration Effect Of Casuarina Equisetifolia Shelter Forest In Different Coastal Gradient

Casuarina equisetifolia, introduced abroad into the southeastern coastal area since 1950s, has become the important species of coast protection forest, playing important role in defending wind and fixing sand, ameliorating environment, and offering timber. However, the long-term unreasonable management and the bad influences of nature factors led to single component and irrational structure of Casuarina equisetfolia forest belt, and result in aging early, stunting growing, and low-value and low-effectiveness in preventing. This exerts negative influences for the sustainable development of coastal protection forest system. Many researchers focus their studies on the rational structure and function of sustainable coastal protection forest of Casuarina equisetfolia, try to reveal the contributing factors to cause low-value and low-effective forest and probe into its mechanisms. All these studies put scientific basic for rational management for sustainable coastal protection forest of Casuarina eguisetfolia, and meet the demand of the construction of coastal prevent system project.Water deficit is the most problem for vegetable growth in the southeast coastal areas of Fujian. In Chishan Forest within Dongshan Island in Fujian Province, with Li-6400 portable photosynthesis system, we studied photosynthetic rate, transpiration rate, water use efficiency and their affecting factors of the four gradients in the backbone shelterbelts of Casuarina. we also analyzed and discussed transpiration characteristics and the water consumption regulations of different gradients. The main results are as follows:(1)The diurnal variations of transpiration rate of four gradients were one-peak curves and bimodal curves also, the diurnal variation of Transpiration rate in the First,third and forth gradients showed a one-peak curve, and the second gradient showed one-peak curves and bimodal curves also, Usually peak in the 12:00 to 14:00。Daily average transpiration rate of the first gradient was higher in May, June, July and November, the second gradient was higher in May, June, August and September and the third and fourth gradients were higher in June, July, August and September. The average transpiration rate in the month of 5～10 Sort for size: the second gradient> third gradient> fourth gradient> the first gradient.(2)The water use efficiency in the first gradient was weak bimodal curve, the first peak appears in the September. The trends of third and fourth gradients were Similar to the first gradient, showed a clear bimodal curve, the peak appears in the July and November. The seasonal variations of WUE in the second gradient changes more complex, was multi-peak curve. The decreasing orders of the max daily average water use efficiency were as follows: the first gradient(4.340mmol·mol-1),fourth gradien(t3.995mmol·mol-1),the second gradien(t3.973mmol·mol-1),third gradient(.3.892mmol·mol-1). The average water use efficiency from May to September were ranked as follows: the first gradient>the second gradient>fourth gradient>third gradient. (3)Because many environmental factors and physiological factors together affect on the physiological process of plants, the key affecting factors of transpiration rate were changing in different months and growth stages. Through the methods of stepwise regression analysis and correlation analysis, it was known that The key factors of different gradient'transpiration were different too, mainly including air temperature, air relative humidity, photosynthetic active radiation and stomatal conductance.(4)With the Photosynthetically active radiation increased, the transpiration rate of Casuarina branchlet has been in an upward trend; the transpiration rate increased rapidly when PAR in the 0 to 200μmol·-2·s-1, and the transpiration rate increased relaxation when PAR was higher than 200μmol·-2·s-1 ,even in the Light intensity conditions of 2000μmol·m-2·s-1,Transpiration rate also does not appear saturated phenomenon , Description Casuarina eguisetifolia is Hi light plant, Transpiration rate from the Light intensity limit under 2000μmol·m-2·s-1.(5)Based on the study of Relevance of Transpiration dynamics and environmental factors in Casuarina forest, to establish the transpiration - Environmental Coupling Model, to explore the seasonal variation of transpiration water consumption patterns, proposed model of optimal water management and collaborative management technique, was the key to the operation and management of Casuarina shelterbelt ecosystem. Advice to strengthen the study of Shelterbelt Water management, by Artificial regulation to improve the situation of forest, making full use of limited water resources in Sandy coast,Improving forest productivity and Protective performance, promoting reasonable cycle of water, maintenance a long-term stability of soil moisture and the sustainable use of forest land.