次生林概念与生态干扰度

近一个世纪强烈的人为干扰使世界范围内的原始林面积锐减,次生林已成为中国乃至世界森林资源的主体.虽然在文献与现实中"次生林（Secondary forest）"被广泛使用，但次生林的概念在各个国家，甚至同一国家或地区以及各种不同文献中存在相互矛盾的情况，这给次生林研究与经营实践带来诸多不便;而不准确的次生林定义也为与各个层次的决策制定者及公众之间的交流带来了障碍.本文在查阅大量国内外关于次生林概念文献的基础上，结合近年来关于次生林生态与经营研究实践，综合分析了次生林概念的不确定性，同意以往次生林定义中的基本内涵，并认为：次生林是由于人为破坏性干扰或异常自然干扰使原始林固有的林分结构、物种组成或基本功能发生了显著变化，经过天然更新或人工诱导天然更新恢复形成的林分.但该定义中仍存在着很多不确定性, 如:怎样的干扰为"人为破坏性干扰"和"异常自然干扰";"林分结构、物种组成或基本功能"发生了怎样的变化为"显著变化";"人工诱导天然更新"中"人工"参与的成分比例如何等.次生林概念是在20世纪初由植物演替学家提出，当时未考虑干扰的持续性;而实际上，无论是次生林还是原始林，均是森林生态系统演替过程中的某一状态，在现代森林生态系统研究中，应重新规范"次生林"的概念.考虑到"次生林"定义的不确定性或困难性，建议使用"森林自然度"或"森林生态系统成熟度"或"森林干扰度"来表达现实森林所处的状态，但该方面的研究与实践尚需加强.

Conception of secondary forest and its relation to ecological disturbance degree

With the past century's continued destruction of primary forests,secondary forests became the major forest resources in China and all over the world.There is a considerable ambiguity or confusion with regard to the conception of 'secondary forest' in different countries or regions,although this term has been used worldwide for more than a century.This fact is inconvenience for the researches in ecology and forest science.Additionally,the imprecise definition could be a major impediment in communicating with general public and decision-makers.Based on a wide range of literature collection on the conception of secondary forest,as well as the practices and researches of ecology and management of secondary forests,this paper analyzed the uncertainties of the conception of secondary forest,and considered that secondary forests were the forests regenerated through natural regeneration,or through natural processes with minor assisted natural regeneration after the destructive disturbances of original forest vegetations by human be-ings or by extremely natural causes,and the forests display significant differences in forest structure,canopy species composition,and/or functions with respect to the primary forests.However,there are still many uncertainties in the definition of secondary forest,e.g.,how to define the destructive disturbances of human beings and the extremely natural causes,what degrees of the changes of forest structure,canopy species composition or functions are the significant changes for secondary forest formation,and how to determine the contribution of human activity in the artificially assisted natural regeneration.The definition of secondary forests was put forward by the specialists on plant succession,without taking the duration of disturbance into consideration.In fact,whether the primary forests or secondary forests,they are both in some stages or states in the successional series of forest community.Therefore,if the concepts of forest disturbance degree,forest naturalness,or forest ecosystem maturity can be applied in defining secondary forest to express the state of current forests,the uncertainties of the term of secondary forest may be avoided.In order to discuss the issues related to the concepts of secondary forest with ecologists or foresters,the primary concepts of forest naturalness,forest ecosystem maturity,or forest disturbance degree were mentioned,but related research and practice still need to be strengthened.