Báo cáo lâm nghiệp: Water movement and its resistance in young trees of Cryptomeria japonica

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Water movement and its resistance in young trees of Cryptomeria japonica...
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Báo cáo lâm nghiệp: "Water movement and its resistance in young trees of Cryptomeria japonica"Water movement and its resistance in young trees ofCryptomeria japonicaH. Yahata Forestry, Faculty of Agriculture, Kyushu University, ofLaboratory of Silviculture, DepartmentFukuoka, Japan materials to reduce from temperatureIntroduction errors were estimated gradients. Transpiration rates conductance to by the measurement of leaf water vapor and the ambient vapor deficit be-Information about water flow resistance is tween leaf and air. The water flow rates in theessential to understanding and simulating stem at different heights (0.5-2.5 m) were esti-water movement in trees (Yahata, 1987). mated using the relationships between theThere are a number of papers concerned heat-pulse velocity, measured with an automa- tic multichannel recording system (Yahata,with it for some species but few for Cryp- 1984) and the water uptake rates from thetomeria japonica and no data are available severed basal stem at the end of a series ofon the gradient of water potential in measurements of the intact tree. Sapwoodintact stem. This study was undertaken conducting area was measured by using a dyeto examine whether the resistance in (1% solution of acid fuchsine).stems would be regarded as substantially Water flow rate, Q, is customarily expressedconstant all day long and to find a simple Ohm’s law analogy with resistance, R, as anequation to predict the effect of stem form and the water potential gradient, Δψ, in the fol- lowing equation (eqn. 1). Q (Δψ-ρgh)/R,on it. = where pgh is the gravitational potential at a height of h (m). By using the above equation with the water flow rate in the stem in place of Q and the gradients of water potential betweenMaterials and Methods soil and leaves, .1 or between rootstock > 1 s- ’ and leaves, dyr the resistance of total path- ,, r- and between root and leaves, R,, way, bRetween sfac!14 yr old C. japonica trees growing in a planta- soil and root, R were de- and S+ntion of high stand density about 6650 stems per termined, respectively.ha were used. Psychrometer sensors (Wescor Provided that the relative resistance r, (m- ), 2PCT55-30) were used with an automated defined by Jarvis (1975), is constantrecording system for measuring the water as throughout a stem with a l ...