森林木质藤本数量过度增长的机制与生态效应

Mechanisms and ecological consequences of the over-increase of lianas in forests

关键词:  木质藤本, 干扰, 全球变化, 森林健康, 森林管理

Key words:  liana, disturbance, global change, forest health, forest management

摘要:

木质藤本是维持森林物种多样性的组成部分。近年来,热带、亚热带森林尤其是次生林内的木质藤本数量的过度增长给森林的恢复和健康发展造成了威胁。至今,国内尚少有研究对森林木质藤本过多的现象、增长机制与生态效应进行综合认识。该文梳理国内外相关文献,从木质藤本数量增长的机制与生态效应进行分析和总结,综合相关研究认为:(1)木质藤本数量的增长与干旱化加剧、大气CO₂浓度上升、自然干扰和森林破碎化有关,在环境变化的情况下,木质藤本在形态、行为、生理等方面比树木更具优势,表现为更快的生长速率、更强的繁殖力和可塑性以及资源利用效率。(2)木质藤本主要通过遮荫胁迫、资源竞争和机械压力与损伤等方式对树木造成影响。(3)木质藤本过度增长在个体水平上会阻碍树木生长、生殖并引起树木死亡,在群落水平上会改变物种组成、降低多样性,在生态系统水平上会降低森林碳储量,改变碳、矿质养分和水分循环过程等。因此,建议结合野外长期监测与控制实验开展木质藤本数量动态与环境变化关系、森林干扰对木质藤本生长的影响、木质藤本对环境变化的响应及适应机理、木质藤本数量过度增长的生态效应评价研究。同时,应积极探索合理的森林木质藤本管控方法,为森林管理和恢复等方面的宏观决策提供科学依据。

Abstract:

Lianas are one of the components in maintaining forest diversity. The over-increase of lianas in tropical and subtropical forests, especially in secondary forests is threatening the restoration and healthy development of forests. Few domestic researches make a comprehensive evaluation on the mechanism of the over-increase of lianas and negative effects on forests. In this paper, we reviewed and summarized the related researches on mechanisms and ecological consequences of the over-increase of lianas both at home and abroad. Based on the relevant studies we hold the opinions:(1)The increase of lianas can be corelated with drought severity, elevated atmospheric CO₂, increased natural disturbance(gaps)and forest fragments. Lianas possess the advantages of rapid growth, strong reproductive capacity and phenotypic plasticity, and high resource use efficiency under the altered environment. Thus, the favorable environment and inherent advantages can contribute to the increase of lianas.(2)Lianas compete with trees by means of shading stress, resource competition and mechanical loading, abrasion, and strangulation, which all may increase the mortality of trees.(3)The over-increase of lianas can negatively affect the tree growth, reproduction, and survival; at community level, lianas can alter tree community composition and decrease community diversity; at ecosystem level, lianas can ramify forest ecosystem function by decreasing carbon storage and altering carbon, nutrient, and water cycling. Therefore, we recommend that future studies should be aimed at the correlations between population dynamic changes of liana species and environmental changes, the effect of forest disturbance on the growth of lianas, responses of lianas to the environmental changes and the adaption mechanisms, comprehensive evaluation on the ecological consequences of the increase of lianas by means of long-term dynamic monitoring plots and controlling experiments. It is also essential to find appropriate management and control strategies of the over-increase of lianas so as to provide reference for forest management and forest ecological restoration.