干扰对高山林线再形成过程的影响

Impacts of disturbances on alpine timberline reformation.

高山林线是一类典型的生态交错带,因其特殊的结构和功能以及对外界环境的高度敏感性而成为全球气候变化研究的热点之一。本文简要介绍了高山林线的相关概念及其界定,从高山林线海拔位置波动、植被格局变化、生态交错带物种组成变化及其生理生态特征变化等几个方面阐述了干扰对高山林线再形成过程的不同影响,总结了高山林线物种对干扰的两种基本响应方式,即退行和入侵。认为人为干扰在一定程度上弱化了当前气候变暖对高山林线波动的影响,因而在不同地区必须紧密结合当地可能的干扰来讨论高山林线的波动,否则结果有可能因误差较大而失去应有的价值。指出该研究在高海拔地区进行植被恢复的指导意义。

With special ecological structures and functions, alpine timberline, a kind of ecotones highly sensitive to disturbances and environmental changes, has become one of the major concerns in global climate change studies. After reviewing the definitions of alpine timberline, this paper discussed the impacts of disturbances on the reformation of timberline from the aspects of its changes in elevation position, vegetation pattern, species composition, and physiological characteristics. It was suggested that the responses of alpine timberline species to disturbances could be basically summarized in two ways： （1） withdrawing： tree species are replaced by new species （usually herbaceous or bushes） after disturbance, and the tree species will withdraw （downward） or disappear; and （2） inbreaking： non-constructive species replace constructive （keystone） species or spread to surrounding area, especially upward along the altitude. The potential increase of timberline resulted from climate warming is compromised to some extend as a result of disturbances. Therefore, distinguishing various disturbances and their effects with climate change is crucial to understanding not only the reformation process of timberline, but also the causes of current vegetation formation in the areas as well.