Study On Property And Technology Of Physiological Drying Of Living Poplar Plantation

Tn the present work, physiological drying of living Populus alba Linn. var. Pyramdalis Bunge Jiving in Hohhot, Inner Mongolia was explored by controlling water source based on the theory of transpiration. Furthermore, the hydraulic conductivity and embolism of heartwood and sapwood was studied by using XYL’EM-Plus. Water status in heartwood and sapwood was also probed by Micro MR time-domain NMR measurements. There were several main conclusions as below.(1) Physiological drying process based on transpiration was obviously faster than air drying process during the first8days.30.31%water in trunk of living trees could be discharged. The method of cutting off water and peeling (P. alba. D), according to the test, was the optimal physiological drying treatment. The mean moisture content of heartwood and sapwood is20%and29%, respectively, which could meet the basic transportation requirement of moisture content.(2) The hydraulic conductivity of sapwood as well as the loss of hydraulic conductivity had no direct relationship to the length of samples, cross-sectional area of vessel cells.(3) The hydraulic conductivity and embolism of heartwood was very different from sapwood. Water could be discharged in vessels in sapwood. Heartwood, however, had little ability to discharge water in vessels due to embolism. That was also resulting in difficulties for water discharging from heartwood.(4) Based on the physiological drying test, drying rate of P. alba. D was the fastest. Moisture content of dried P. alba. D was more lower than those of P. alba. A, P. alba. B and P. alba. C. Hence, the physiological drying method of cutting off sapwood and peeling was an optimal treatment. Bound water existed with free water in sapwood of P. alba. D at F.S.P. owing to less vapor pressure between heartwood and sapwood and embolism forming in the pathways of water transport. After physiological drying treatment, bound water only existed in sapwood of P. alba. D. Free water was discharged completely from the trunk. But there was a small amount of free water in heartwood.