森林草原过渡带中沙地云杉幼苗在林窗中的环境梯度变化

在我国内蒙古自治区森林草原过渡带中,从林窗内到周围环境进行沙地云杉(Piceamongolica)幼苗的调查以阐明其梯度变化。在沙地森林区,选择了一个形成年龄长达30年的大林窗,从林窗中央向周围森林作2个5m宽的样带,对沙地云杉幼苗动态进行了监测。幼苗距离林窗中心越远,个体越高,数量也越多。在林窗内,有很多幼苗,但是大多数的幼苗在它们长大之前就死亡了。相对于林木高度的动态变化,幼苗的死亡率在样带中的分布基本上有着相似的规律。沿着森林的边缘,幼苗的生长可能由于林窗中边缘光线渗透而得到暂时的提高。文中还讨论了自然森林的更新动态。结果表明在沙地云杉林里林窗干扰带能产生一个非均质的环境促进物种的更新,从而决定了该森林是一个多年龄层次的森林类型。图6参37。

An environmental gradient change of Picea mongolica seedling from the center of a forest canopy gap in forest-steppe ecotone in Inner Mongolia Autonomous Region of China

In sandy forest with a forest canopy gap for a period of over 30 years, the spruce(Picea mongolica) seedlings were monitored on two 5-m- wide transects from the center of a large gap into the surrounding forest. The farther they were to the far center, the taller grew the seedling and the more is the number of seedling. There were many seedlings under the canopy but almost all seedlings died before they grow up. Along the forest edge, growth of seedlings was temporarily enhanced by lateral penetration of light from the gap. The implications for natural forest regeneration dynamics are discussed. Our results prove that in P. mongolica forest a gap disturbance creates a non-uniform environment for regeneration of the species, and determines that the forest was a non-even aged forest.