Callaghan Terry V, Crawford Robert M M, Eronen Matti, Hofgaard Annika, Payette Serge, Rees W Gareth, Skre Oddvar, Sveinbjörnsson Bjartmar, Vlassova Tatiana K, Werkman Ben R
Ambio. 2002 Aug;Spec No 12:3-5.
The tundra-taiga boundary stretches for more than 13,400 km around the Northern Hemisphere and is probably the Earth's greatest vegetation transition. The trees that define the boundary have been sensitive to climate changes in the past and models of future vegetation distribution suggest a rapid and dramatic invasion of the tundra by the taiga. Such changes would generate both positive and negative feedbacks to the climate system and the balance could result in a net warming effect. However, the boundary is becoming increasingly affected by human activities that remove trees and degrade forest-tundra into tundra-like areas. Because of the vastness and remoteness of the tundra-taiga boundary, and of methodological problems such as problematic definitions and lack of standardized methods to record the location and characteristics of the ecotone, a project group has been established under the auspices of the International Arctic Science Committee (IASC). This paper summarizes the initial output of the group and focuses on our uncertainties in understanding the current processes at the tundra-taiga boundary and the conflicts between model predictions of changes in the location of the boundary and contrasting recently observed changes due to human activities. Finally, we present recommendations for a coordinated international approach to the problem and invite the international community to join us in reducing the uncertainties about the dynamics of the ecotone and their consequences.
苔原 - 针叶林边界在北半球绵延超过13400公里，可能是地球上最大的植被过渡带。界定该边界的树木过去对气候变化很敏感，未来植被分布模型表明针叶林将迅速且剧烈地侵入苔原。此类变化会对气候系统产生正负两方面的反馈，其平衡可能导致净变暖效应。然而，该边界正日益受到人类活动的影响，这些活动砍伐树木，将森林苔原退化为类似苔原的区域。由于苔原 - 针叶林边界地域广阔且地处偏远，加之存在诸如定义不明确以及缺乏记录生态交错带位置和特征的标准化方法等方法学问题，一个项目组在国际北极科学委员会（IASC）的支持下成立了。本文总结了该小组的初步成果，重点关注我们在理解苔原 - 针叶林边界当前过程时的不确定性，以及边界位置变化的模型预测与近期因人类活动观察到的相反变化之间的冲突。最后，我们提出了针对该问题的协调一致的国际方法建议，并邀请国际社会与我们一道减少关于生态交错带动态及其后果的不确定性。
