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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。
Eight years after the closure of Pinus tabulaeformis forest, the photosynthesis, transpiration, chlorophyll content and growth of Pinus tabulaeformis decreased significantly after 2-3 years of over-pruning (leaving 2 branches only) or over-pruning and detached leaves , The content of soluble sugar and starch in conifer decreased but the content of fat and protein increased but the total caloric content increased in pine needles. The weight gain of Larvae dendrolimi larvae increased after feeding on their needles. Rational pruning can not only improve the photosynthetic strength and tree vigor of Pinus tabulaeformis, but also enhance insect resistance. The study also found that the fourth annual shoots of Pinus tabulaeformis annual coniferous and photosynthetic products the most, to enhance the tree vigor and insect resistance is extremely important, should be the focus of protection, and thus put forward a reasonable index of Pinus tabulaeformis.