Studies On The Modulation Mechanisms Of Water Consumption Of Water Capacitance And Xylem Cavitation And Embolism In Three Tree Species

The characteristic of xylem conduit cavitation and embolism and water capacitance reflect the efficiency of water transportation and the function of water storage in tree species. By studying on their characteristic and expounding the coordination relationship with the water consumption, we may further explore and promulgate the laws of water consumption and their internal controlling mechanisms in tree species. It was aimed at to provide a theoretical foundation and technique instructor for the water management of tree species ecological and economically in forestry.The paper was studied on the modulation mechanisms of water consumption in three tree species (Pinus tabulaeformis, Platycladus orientalis, Acer truncatum)of xylem conduits cavitation and embolism and water capacitance. The studies were carried out the technique route by experiments on-farm and in laboratory on different scales. The advanced techniques of the world have been adopted in the projects. The thermal dissipation probe method (TDP) has been used for measuring the sap flow of tree. The acoustic emission (AE) method has been adapted to check and measure the wave parameter of acoustics emission from the xylem conduits cavitation. The flashing method has been adopted for measuring the percentage loss of hydraulic conductivity (PLC) of embolism. The water content and its potential method have been adopted for measuring the water capacitance of tree tissues. The researches work has been achieved synchronization and systematization.The research result was explained the characteristics of occurrence and refills of xylem cavitation and embolism and water capacitance, and the cooperativeness controlling mechanisms on the water consumption in three tree species.The results indicated that while the xylem cavitation occurs, the maximums water potential of branch of Pinus tabulaeformis , Platycladus orientalis, and Acer truncatum are respectively as follow: -0.8MPa,-1.0MPa and -0.5MPa. The acoustic emission frequency spectrum scope of the xylem cavitation concentrates in 190 KHz ~ 300 KHz. The acoustic emission amplitude scope concentrates in 30 ~ 70dB, and the primarily events scope were in 30 ~ 50dB. The acoustic emission energy is in the majority event by 0 ~ 50mv*us.While the embolism occurs, the critical water potential of branch of Pinus tabulaeformis, Platycladus orientalis and Acer truncatum appearance respectively for -0.85 MPa,-2.05 MPa and -0.11MPa. The degree of embolism is low at the 6:00 and 18:00, and it is severity during the daytime from 10:00 to 14:00. Because of the average water potential of branch appearance frequently below -1.0MPa in trees growing under the naturally condition, the xylem cavitation and embolism occur frequently and paroxysmal in the three sample tree species.The xylem cavitation and embolism occurs more frequently during the daytime than that of during...