过度修枝对油松生长及其抗虫性影响以及合理修枝探讨

油松幼林封山八年后,连续2-3年过度修枝(只留2轮枝)或过度修枝又失叶后,油松的光合强度、蒸腾强度、叶绿素含量及生长量都显著下降,针叶中可溶性糖、淀粉含量下降,脂肪与蛋白质含量反而增高,松毛虫食物的总热量增大,取食其针叶后,赤松毛虫幼虫体重增长率提高。合理修枝不仅能提高油松的光合强度与树势,还能增强抗虫性。研究还发现,油松第四轮枝的一年生针叶量与光合产物量最多,对增强树势与抗虫性极为重要,应予以重点保护,并据此提出了油松合理修枝的指标。

THE EFFECT OF OVER-PRUNING ON PINUS TABULAEFORMIS GROWTH AND ITS RESISTANCE TO DENDROLIMUS,AND ITS RESONABLE PRUNING

The photosynthesis rate, transpiration rate, chlorophyll content and treegrowth are all found to be decreased remarkably by 2-3 years' repeated over-pruning (only two branch whorl reserved) or over-pruning plus defoliation inPinus tabulaeformis stand which has been closed to human activities for eightyears. As a result, the decreased content of soluble carbohydrate and starch,and the increased contents of fat and protein make the total quantity of heatin needles as insect food increased. This benifits the weight growth rate ofDendrotimus larvae, and weakens tree resistance to insect. Therefore not onlythe photosynthesis rate and tree vigour, but also its resistance to insect couldbe increased through reasonabl pruning. Experiments show that most current needles of Pinus tabulaeformis are onthe fourth branch whorl, and they are extremely important to accumulatingphotosynthetic products. Based on the experiment result, the standard of rea-sonable pruning of Pinus tabulaeformis is discussed.