恒被林及其育林体系

Continuous Cover Forest and Its Silvicultural Systems

恒被林很早就被提出来了 ,但其育林体系直到现在才得到推行 ,这个育林体系不包括皆伐 ,要求林冠永远地覆盖林地 ,而不使土壤裸露。这个育林体系既能维护森林环境 ,不影响森林景观和森林结构的变化 ,又能培育与收获木材 ,很符合现代的森林经营观念。英国的恒被育林体系包括 :群状与单株择伐 ,渐伐 ,带状与群状渐伐 ,有计划的群状采伐 ,伐块范围不超过 0 .2 5hm2 ,采用人工栽植或天然更新或两者结合以形成复层异龄混交林。对于同龄纯林可采用上述育林体系进行改造。

The concept of Continuous Cover Forest has been proposed for a long time.But,it was extended as a new silvicultural system only few years ago. In this silvicultural system,clear felling is not allowed and continuous cover of stand canopy on the land is required without exposure of ground.Under this silvicultural system the forest environment,forest landscape and forest structure are not dramatically distructed along with the developing and yielding of woods,which just matches the modern idea of sustainable forest management.The silvicultural system of Continuous Cover Forest in U.K. includes different logging measures,such as group or single tree selection,shelterwood,strip and group shelterwood and planned group felling,with maximum felling acreage less than 0.25 hm 2,The planting or natural regeneration or their combination are adopted for the reforestation of the cutover site,so that the forest structure over a whole area is mixed in species,multiple in storey and uneven in age.The even aged pure plantations can be modified and converted into the mixed and uneven aged forests by employing the above mentioned silvicultural system.