Abstract: In Heilungjiang forest regions, the young forests are heavily damaged by rodents’ grazing on bark. It was found that the brown-backed vole is the most important species.In the present study we found out that the changement of the numbers of this vole depends upon the different conditions of forest canopy density. The higher the canopy density, the lower the vole's numbers as well as the rodent damage. On the contrary, the lower the canopy density, the higher the vole's number and, of course, its damages. Under the direction of this rule, we believe that the rodent damages may be controlled by managing the forest canopy in afforestation, and two measures have been suggested: 1) In reforestation,the trees should be closely planted in order to make the young forest be closed in early time.

摘要： 黑龙江省林区林木鼠害危及多种树种(图1—a、b),冬季啃食幼树树皮损失严重。(舒凤梅1975、1979)。为害鼠种主要为棕背(鼠平)(Clethrionomys rufocanus),其他各种鼠为红背(鼠平)(C.rutilus)、东方田鼠(Microtus fortis)、大林姬鼠(Apodemus Peninsulae)、黑线姬鼠（A.agrarius）和花鼠(Eutamias sibiricus)。以往多采用化学药物防治。本工作发现该鼠的数量与林地郁闭度有密切关系，故而探讨了利用调整鼠类栖息环境，预防林木鼠害发生的途径。