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低产林是由如下几种原因造成的:一是重复采伐和超量采伐;二是火灾的破坏和病虫害的侵袭;三是土层瘠薄地带,郁闭度0.3以下的疏林地或多代萌生无培育前途的林分。低产林的生产力是很低的。其特点是中慢生树种每公顷年生长量不超过3立方米,慢生树种每公顷年生长量不超过1.5立方米,而且郁闭度都在0.3以下。从各地情况来看,白桦低产林出现得较多,落叶松低产林出现得较少。这是因为,如果是落叶松、白桦
Low-yield forest is caused by the following reasons: First, repeated logging and over-harvesting; second, the destruction of fire and pests and diseases; Third, the soil infertile areas, canopy density below 0.3 sparse or multi-generation sprout Cultivate the future of the forest. The productivity of low-yield forests is very low. Its characteristics are slow-growing trees per hectare of annual growth does not exceed 3 cubic meters, slow-growing trees per hectare of annual growth does not exceed 1.5 cubic meters, and canopy density are below 0.3. From all over the situation, appeared more low-yield birch forest, low-yielding larch appeared less. This is because, if it is larch, white birch