修枝对尾巨桉生长及光合生理的影响

Effects of pruning on the growth and photosynthetic physiology of Eucalyptus urophylla ×E. grandis

采用裂区设计连续实施2次人工修枝,研究了不同修枝强度(不修枝、轻度修枝(修去活枝冠层的1/4下层枝条)、中度修枝(修去活枝冠层的1/3下层枝条)、重度修枝(修去活枝冠层的1/2下层枝条)对尾巨桉生长及光合生理的影响。结果表明:修枝强度对胸径、树高和单株材积均无显著影响,其中主区重度修枝的胸径与不修枝基本一样,二者大于轻度修枝和中度修枝;树高基本一样;单株材积变化趋势与胸径变化趋势一致。第1次修枝以重度修枝对生长的促进作用最大,先后2次修枝互作效应较好的是重度修枝-重度修枝、重度修枝-不修枝和不修枝-不修枝3个组合。4种不同修枝强度的净光合速率变化与生长变化趋势一致,主要受瞬时羧化效率影响;蒸腾速率不随修枝强度改变而变化;水分利用效率变化与生长变化趋势一致,其差异主要由净光合速率引起。综合考虑尾巨桉的水分利用效率、生长量最大化和可获得无节材长度3个因素,认为先后2次实施重度修枝-重度修枝是最好的修枝方式。

With a splitplot experimental design, this paper studied the effects of different prun ing intensities （no pruning, CK; light pruning, cutting 25% of whole canopy; moderate prun ing, cutting 33.3% of whole canopy; and heavy pruning, cutting 50% of whole canopy） on the growth and photosynthetic physiology of Eucalyptus urophyUa x E. grandis. Pruning intensity had no significant effects on the diameter at breast height, tree height, and single tree volume. In the main plots, the diameter at breast height under heavy pruning was almost the same as that of CK, and was larger than that under light pruning and moderate pruning. The tree height in all treat ments was basically the same, and the single tree volume had the same variation trend as the diameter at breast height. Heavy pruning had the best promotion effect on the tree growth in the 1 st pruning practice. After carrying out the 2nd pruning practice, the tree growth under heavy pruningheavy pruning, heavy pruningno pruning, and no pruningno pruning was slightly bet ter than that in other treatments. Under the four pruning intensities, the net photosynthetic rate had the same variation trend as the tree growth rate, being mainly affected by instantaneous carboxylation efficiency. The transpiration rate was not changed with pruning intensity.The wateruse efficiency had the same variation trend as the tree growth rate, and the variation was mainly induced by the difference of net photosynthetic rate. Considering the water use efficiency, maxi mum growth, and length of wood without knot, it was suggested that the heavy pruning-heavy pruning could be the best manual pruning mode for the cultivation of E. urophyllaxE, grandis.