论文部分内容阅读
一、树木对光照强度的适应 根据树木对光照强度适应关系,可以分为三种生态类型: (-)阳性树:凡在强光环境中才能生育健壮,而在荫蔽和弱光条件下生育不良的树木,称为阳性树。阳性树一般枝叶稀疏、透光,性喜光,幼年生长快,自然整枝良好,树皮通常较厚,叶色较淡,容易郁闭成林,竞争力强,多为先锋树种,植株开花结实力较大,林木分化和自然稀疏都较早而强烈,一般生长迅迅,寿命较短。阳性树种有杨、柳、刺槐、臭椿、桦木、麻栎、油松、杉等。 (二)阴性树:在较弱的光照条件下比在强光下生长得好的树木,为阴性树。阴性树多生长在潮湿、背阴或林内,故有一定耐阴力,能在混交林的树冠遮被下生长,幼年都有较慢的生长阶段,郁闭与成林均较晚。在幼林中与喜光的阳性树竞争力弱,易被压抑,但在受压抑中不象阳性树那样易于枯死,如经过间伐不再受遮被时,就会迅速生长。
First, the adaptation of trees to light intensity Adaptation of light intensity according to trees, can be divided into three types of ecology: (-) Positive tree: where strong light in order to give birth to robust, and shade and low light conditions, malabsorption Trees, called positive trees. Positive trees generally sparse branches, light, nature, light, fast growth of young, natural pruning good, the bark is usually thicker, leaf color lighter, easily closed forest, competitive, mostly pioneer species, flowering and fruiting plants Larger, natural differentiation and natural sparse are earlier and stronger, the general growth rapid, short life expectancy. Positive trees are poplar, willow, acacia, Ailanthus, birch, oak, pine, fir and so on. (B) of the negative tree: in the weaker light conditions than in bright light well-grown trees, as a negative tree. Negative trees mostly grow in dampness, shade and forest, so they have some resistance to shade. They can grow under the canopy of mixed forest, and have a slower growth stage in juvenile. In the young forest and the positive light of the positive tree is weak, easily suppressed, but not suppressed in the positive tree as easy to die, such as after thinning is no longer covered, it will rapidly grow.