在林区采伐木材。常常看到一些树的外表正常,但采伐下来一看,树干是空筒子,成为价值不大的废材。无论是针叶树还是阔叶树,都可能出现这种情况。空筒树是一种病害造成的。如落叶松,它的木材虽然坚硬,但是有一种松针层孔菌,能够从树木的伤口断枝处侵入心材木质部,这种菌分泌一种腐蚀液,可使树木腐朽,并从树干中心向周围扩大,把坚硬的木材变软,出现白色小窝,最后全部空掉,形成只有树皮和边材的空筒子。杨树也有一种木腐菌,危害树木 Harvesting timber in the forest. Often see the appearance of some of the trees normal, but logging down look, the trunk is empty cheese, become valuable waste. This can happen either in conifers or broad-leaved trees. Empty tube tree is a disease caused. Like larch, its wood is hard, but there is a pine needle-hole fungus that can invade the xylem of the heartwood from the wounds of the tree that secrete an etchant that decays the tree from the center of the trunk to the surroundings Expand, soften the hard wood, white nest appeared, and finally all empty, forming only empty bark and sapwood. Poplar also has a wood rot that harms the trees