退化植物群落结构及其物种组成在人为干扰梯度上的响应

Changes of Structure and Species Composition of Degraded Plant Community along Disturbance Gradients of Different Intensities

在岷江上游大沟流域 ,沿着人为干扰梯度 ,调查了退化榛栎群落的结构及其物种组成变化。结果表明 :(1)除密度外 ,群落木本层的结构特性 (密度、高度、生物量、基径面积和物种多样性 )与干扰强度的增加呈负相关 ,而其草本物种多样性、生态优势度呈正反应 ,但地上生物量变化呈现相反的趋势 ;(2 )根据群落内植物种群密度 (或盖度 )在干扰梯度上的响应变化 ,群落内 4 7个种可基本上分成 3个反应种组 :16个为扩展种 (invasivespecies) ,随干扰强度增大而种群数量明显增多。 6个为敏感种 (sensitivespecies) ,随干扰强度增大而种群数量明显减小 ,若干扰继续下去 ,这些种将处于局部濒危状态或局部灭亡。其余 2 5个为忍耐种 (tolerantspecies) ,随干扰强度变化并未表现出明显的种群数量变化。相关的观察和分析暗示出 ,在持续的人为干扰体系作用下大沟流域植物群落退化的终点很可能是多刺、多毛灌木为优势的刺灌丛 ,而不是一般认为的裸地或草坡。 (3)群落退化主要表现为结构的退化 ,而物种组成变化相对滞后 ,表明群落结构较物种组成对干扰的响应更敏感 ,因而可作为干扰的指示者。文中对长期人为干扰下退化群落的恢复和重建的途径和方法也进行了讨论。

Structure and species composition of degraded plant community, along a human-induced disturbance gradient in Dagou watershed of the upper reaches of the Minjiang River, were investigated. In general, attributes of woody-layer structure (density, height, basal area, species diversity and biomass) were negatively related with increasing disturbance. Herbaceous layer attributes (coverage, biomass, diversity, ecological dominance etc.) responded positively. This may be common response of various plant communities on disturbance except their density attribute. Although individual woody species exhibited a range of responses to disturbance, overall species compositional changes were not related directly to the intensity of disturbance. According to their response along the human-induced disturbance gradient, 47 species were classified into three behavioral species groups: 16 in the invasive, 6 in the sensitive and 25 in the tolerant. Some useful conclusions were drawn: (a) degraded endpoint of scrub community in Dagou watershed may be marquises in which dominant species are those shrubs in the invasive species response group; (b) plant community degraded as a major form of structural decline, its species compositional change have hysteresis effect, and community structure may be more sensitive indicator to disturbance than species composition. How to restore and rehabilitate the degraded community has also been discussed in the paper.