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Pruning as a basis for measures in forest management, and so has a great significance to improve the forest material, improve the tree stem form. This thesis is to study, Europe and the United States 107 Yang (Populus × euramericana cv. '74 / 76 '), respectively, in the two provinces of Hebei, Shandong of Europe and the United States 107 Yang to carry out mild p1 (trim crown length 1/6), moderate p2 (repair off the crown length of 2/6), intensity p3 (are trim crown length of 3/6), severe p4 (trim crown length 4/6) pruning and not pruning (ck) comparison test, determination of tree height, diameter and other morphological and measured physiological parameters of poplar under different pruning intensity in the upper single-leaf net photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency and effective leaf area index, stem sap flow rate, and Select the average standard wood stem analysis, trunk Volume is calculated relative growth rate, a different trunk height radius growth relative amount of logs Taper. The results show that: (1) different pruning intensity on tree relative growth rate affect the overall difference was not significant (P lt; 0.05), indicating that nutrition tip growth mainly from the upper canopy of foliage; relative growth of different pruning intensity DBH rate differences highly significant (P lt; 0.01), showed: Pruning the greater strength, diameter at breast height relative growth rate is smaller. (2) the impact of different of pruning intensity of net photosynthetic rate and other physiological parameters is significant. ① pruning the upper single leaf canopy net photosynthetic rate improved to some extent, and with pruning intensity increases, the net photosynthetic rate increased. (2) At the same time pruning also increased transpiration rate, especially around noon, part of the pruning process transpiration rate remained high. ③ analysis show that the pruning to a certain extent reduced saturated forest single leaf water deficit, making the noon photosynthetic decline reduce, or even lunch break phenomenon stop, into a single peak curve, indicating that pruning allows limited moisture supply to the whole plant leaf relative sufficient, a certain sense of increased stomatal conductance, increase the degree of stomatal opening, is conducive to the improvement of net photosynthetic rate and transpiration rate. (4) similar proportion of net photosynthetic rate and transpiration rate increases, resulting in a single leaf-scale water use efficiency and less individual single leaf transpiration rate increases the proportion is much higher than the net photosynthetic rate, resulting in partially treated instantaneous water use efficiency is lower than in the control. (3) different pruning intensity on material product relative growth rate significantly different the reasonable strength pruning can promote a relative increase in the rate of growth, volume can be increased by 9.04%, contrary excessive pruning is unfavorable volume growth. (4) the impact of differences of different of pruning intensity of effective leaf area index highly significant decreases continuously with pruning intensity increases, the effective leaf area index. (5) Europe and the United States under different pruning intensity of the liquid flow rate of 107 Yang very different testing ground I severe pruning in the the 5,6,7 month liquid flow rate is about control of the half, and even smaller after pruning photosynthetic increased, indicating relatively abundant supply of water, a certain sense of pruning can effectively reduce the transpiration of the whole plant trees, to improve the efficiency of water use monoclonal scale. Pruning trees with water conservation, with some drought prevention, pruning is also a water-saving measures can be said. (6) the different heights resolve the disc diameter growth with pruning strength of the different fluctuations on parsing wooden trunk (0-11m) analysis, can be seen near the lower diameter growth with the pruning intensity decreases, the diameter of the trunk upper volume growth for pruning than not pruning. (7) pruning effectively increasing timber cut relative degree decrease, so that the smaller the relative log taper, greatly reduced trunk taper, straight trunk full, and also greatly increased the rate of out of wood.
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