【作者】 孙尚伟；

【导师】 尹伟伦； 夏新莉； 刘晓东；

【作者基本信息】 北京林业大学 ， 森林培育， 2010， 博士

【摘要】 中国是杨树人工林面积最大的国家。近十年来,我国杨树栽植面积不断扩大。欧美杨107(Populus×euramericana cv.’74/76’)因其具有优质、速生、丰产等特点,在山东、河北、河南等多省大面积栽植,并且在林木生长前期多进行农林间作。然而在实际生产当中,普遍存在缺乏有效的科学管理措施的问题。修枝作为重要的抚育措施,能够培育优质良材,有效地提高出材率。目前对于欧美杨107的修枝缺乏系统的研究,存在修枝随意性和盲目性等问题。因此,本研究以确定合理修枝强度为目的,分别在河北衡水市和保定市、山东德州市、河南孟州市对欧美杨107(4-5a)进行四种不同强度的修枝处理,分别为轻度修枝(修去冠长1／6)、中度修枝(修去冠长2／6)、强度修枝(修去冠长3／6)和重度修枝(修去冠长4／6),以不修枝为对照,对欧美杨107和林下小麦、玉米的生长生理进行了研究,结果表明：(1)修枝后胸径生长率显著降低,四种修枝强度在修枝两年后的胸径生长率均低于对照,修枝后第一年,胸径生长率基本随着修枝强度的增加而降低,且差异显著(P<0.5)。修枝第二年强度修枝、重度修枝胸的胸径生长率高于对照,轻度修枝、中度修枝与对照接近。修枝对高生长仅在修枝第一年具有一定促进作用,增幅随着修枝强度的增加而增大,但差异并不显著(P>0.5)。(2)修枝对材积生长有一定影响。修枝两年后,强度修枝的材积相对生长率最大,比不修枝增加了1.25%-4.52%。在修枝当年,中度修枝或者强度修枝会促进材积生长,其它修枝强度则会减缓材积生长。修枝后第二年,强度修枝对材积生长仍有明显的促进作用,而其余修枝强度则均会影响材积的生长,但与第一年相比,降幅减小。修枝能有效促进树干中上部径生长,降低树干的尖削度,能有效提高木材出材率。且这这种促进作用仅在修枝第一年较为明显。(3)相同含节率的死节对木材顺纹抗压强度及抗弯强度的降低程度均比活节大；木节对抗弯强度的降低程度大于抗压强度；无论死节还是活节,含节率越高,木材顺纹抗压强度和抗弯强度降低程度越大。由于修枝能有效减少木材中死节的数量并减小活节的直径,因而修枝后能有效增加木材的抗弯强度与抗压强度,提高木材质量。(4)修枝后总叶面积显著减少,效叶面积指数分别为不修枝的58.59%-94.34%修枝后树冠总蒸腾量显著降低。重度修枝的树干液流速率仅相当于不修枝的1／3,中度修枝仅相当于不修枝的2／3。(5)欧美杨107不同冠层叶片的光合速率、蒸腾速率、气孔导度、瞬时水分利用效率均表现为上部>中部>下部。修枝后叶片光合速率、蒸腾速率、气孔导度等光合特性均呈不同程度的增加,增加幅度受修枝强度、树龄、叶片部位及土壤水分状况等因素影响。修枝强度越大,叶片所在枝条部位越靠近树冠顶部,树龄越大,增加幅度也越大。(6)修枝能有效增加林下光合有效辐射。能有效增加林下作物光合速率、蒸腾速率、气孔导度,且增幅随着修枝强度的增加而增加。修枝后日平均净光合速率分别比不修枝提高2.34%～62.63%,玉米提高41.84%～90.78%。修枝能显著促进小麦、玉米增高、增粗、增重,且越到作物生长后期修枝对作物生长的促进作用越明显。另外,修枝对玉米生长的促进作用大于小麦。修枝能使林下作物大幅增产,轻度修枝、中度修枝、强度修枝、重度修枝下小麦分别增产11%、77%、125%、171%,玉米分别增产46%、100%、232%、399%；修枝后玉米主要通过增加穗数,小麦主要通过增加粒重和穗粒数增产；修枝后玉米增产幅度大于小麦。更多还原

【Abstract】 The effects of pruning on poplar and crops were investigated to demonstrate whether pruning could act as an optimization measure for promoting growth of them. Four and Five-year-old poplar(Populus X euramericana cv.’74/76’) were pruned to remove 0,1/6,2/6,3/6 and 4/6 of the green crown length in Hebei,Henan and Shandong province of China.The growth and physiological characteristic of poplar and crops (wheat and mazie) planted under the trees were investigated.The results indicated that:1. The difference of relative tree height growth rate in different pruning treatment was not significant, this demonstrated that the nutrition for apex growth mainly came from the branches and leaves of top layer; the difference of relative growth rate of DBH was significant, that is, the higher pruning intensity, the lower DBH relative growth rate.2. The influence from different pruning intensity on the net photosynthetic rate and other physiological parameters was significant. The pruning improved net photosynthesis of the single leaf on the middle and top layer of crown in some degree, and with the increased pruning intensity, the net photosynthetic rate also increased. At the same time, pruning increased the transpiration rate, particularly around the noon time, some pruning treatments trees can still keep the relatively higher transpiration rate. The results showed that pruning reduced the saturation water deficit of individual foliage, and increased the leaf stoma conductance, which was propitious to improving net photosynthesis and transpiration rate. As to the water-using efficiency of single leaf, the differences form all pruning treatments were not obviously, even some water-using efficiency of individual leaf from pruned was lower than that from control.3. The difference of relative volume growth rate from different pruning intensity is significant. That means the suitable pruning intensity can increase the volume growth rate, but excessive pruning is disadvantageous to the volume growth.The volume growing rate increase 1.25%-4.52%by pruning intensity of 3/6 of green crown length removed. 4. The Effect of different Pruning intensity on the effective leaf area index was significant. Along with the increasing of pruning intensity, the effective leaf area index decreased gradually.5. The difference of trunk flow rate under different pruning intensity was significant. Based on the data in Site I, the data of trunk flow rate from relative high-intensity pruning trees were just as half as these of control trees in May, June, and July. This indicated that the pruning can effectively reduced the transpiration water volume of whole individual tree in some degree. Although there was no difference between the pruned trees and unpruned trees in terms of the instantaneous water use efficiency at single leaf level, as to the flow rate at whole tree level, the pruning effectively reduced water consumption of trees, and improved the water use efficiency.6. The radial growth of the analyzed trunk discs at different heights was different along with the various pruning intensity. Based on the analysis data from the trunk height from 0 to 11 m, the radial growth decreased in the lower part and increased at the higher part along with the increase of pruning density.Pruning effectively decreased the taper of trunk, that means the relative taper of logs became smaller, and the trunks became full and straight, this increase the timber volume.7. Net photosynthetic rate and transpiration rate of crops increased after pruning,which was less remarkable in the afternoon than in the morning. The height,ground diameter and aboveground biomass of winter wheat and summer maize both increased remarkably, and that of summer maize was higher than that of winter wheat. The yield of crops also increased substantially after pruning, and that of wheat mainly came from thousand grain weight and the number of grain per spike, but that of maize mainly came from spike number. The increased yield of maize was higher than that of wheat, but the total yield was lower than that of wheat. So winter wheat was more suitable for agroforesty system than summer maize.更多还原