摘要
本文对过去所提出的控制欧洲和北美树线位置的因子和植物过程进行了评价。有人认为是由于环境灾害造成的,另一种则认为是树木物质递增受到限制造成的,实际上二者是相辅相成的。这是因为植物所受的伤害、加之物质获取的不利条件及较少的可用物质源最终会导致生物量增加难以维持,而并非立刻死亡。树线达到平衡的位置随气候而变化,但灾难性的事件和人类活动削弱了树线与气候的相关关系,增加了预测其将来位置的难度。在树线或树线以下的多个地理位置开展多树种条件下的野外调控实验对总结解释和预测的一般结论是必须的。
The factors and plant processes that have been proposed to control treeline location are evaluated for European and North American treelines. While often presented as alternative determinants of treeline, the ideas of the increased environmental hazard coefficient and the idea of tree material limitation are considered to be complementary. This is because plant damage, rather than outright death, coupled with difficult conditions for material acquisition and small available material pools, eventually makes accretion of biomass untenable. The location where this balance is achieved varies with climate, but catastrophic events and human activities make correlation with climate tenuous and future predictions difficult. Field manipulation of conditions for many tree species in many geographic locations at and below the treeline are needed to develop generalizations that are both explanatory and predictive.
