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    皆伐与刀耕火种后常绿−落叶阔叶混交林的动态恢复机制

    Dynamics and mechanisms of natural restoration of evergreen-deciduous broadleaved mixed forest following clear cutting and slash-and-burn

    • 摘要:
      目的皆伐与刀耕火种是对森林生态系统造成严重影响的人为干扰方式。本研究旨在比较常绿−落叶阔叶混交林在两种干扰后群落的动态恢复特征并分析其形成机制,以期为森林植被保育和林业生态建设提供参考。
      方法依托不同干扰后恢复20与40年群落内所设立的98个样地,在径级划分的基础上对群落基本特征采用物种多度格局、物种组成、稀疏化丰富度及多度进行描述,并运用多元统计方法分析上述特征在不同恢复群落间的差异性。
      结果不同恢复群落的多度与稀疏化丰富度均存在显著差异(P < 0.05)。在中、小径级植被当中,皆伐后恢复20年群落的多样性指数显著高于弃耕地恢复20年群落;不同恢复过程中植被多度的变化趋势不同,弃耕地恢复过程具有更明显的多度变化,且在不同径级中均达到显著水平。虽然不同恢复的20 ~ 40年过程中群落物种组成的变异性均达到极显著(P < 0.001),但小径级植被较能反映这种变异,同时也能反映物种生态对策的转变。此外,弃耕地恢复过程中上述特征更明显。物种多度格局关系显示,弃耕地恢复群落的优势种具有更明显的优势地位,而采伐恢复过程中物种间的多度差异明显减小。
      结论皆伐后的常绿−落叶阔叶混交林能在短期内展现较高的恢复速率,而弃耕地恢复则在短期受阻后才体现出该特点。这可能与干扰对生物与非生物资源的影响程度有关,表明刀耕火种对群落恢复的影响深远。此外,常绿−落叶阔叶混交林在经历干扰后物种组成的恢复缓慢,但具有一定的秩序。

       

      Abstract:
      ObjectiveWith great impacts on forest ecosystem, both clear cutting (CC) and shifting cultivation (slash-and-burn agriculture) were intensive disturbances. Our work aims to study the dynamics and underlying mechanisms of community characteristics of evergreen-deciduous broadleaved mixed forests (EDBMF) following CC and slash-and-burn. This work was also hypothesized to contribute to forest vegetation conservation and the construction of ecological forestry.
      MethodUsing data from 98 plots of 20- and 40-year-old stands following CC and slash-and-burn, species abundance distribution (SAD), species composition, rarefied richness and stem abundance were applied to characterize community features. These characteristics were compared among different stands and diameter at breast height (DBH) classes with differences measured by multivariate statistical methods.
      ResultThe rarefied richness and stem abundance among those communities were significantly different (P < 0.05): trees with large and intermediate DBH sizes in 20-year-old stand following CC had significant higher stem abundance and rarefied richness values than the 20-year-old stand following slash-and-burn; restoration process following slash-and-burn had changes in stem abundance different from that following CC, also showing significant and more substantial variations. Stands of different recovery stage following the same disturbance also had variation in their species composition at extremely significant level (P < 0.001): along with different restoration progresses, trees with small DBH sizes had relatively strong variations of species compositions, which also reflected shifts in ecological strategy; restoration following slash-and-burn had more obvious and large shifts in species compositions than that following CC. The SAD patterns showed that forest stands following slash-and-burn had higher species dominance, whereas the variations in species abundance declined as restoration from CC progressed.
      ConclusionThe EDBMF undergoing CC displayed higher resilience after disturbance, whereas restoration from agricultural abandon merely exhibited higher recovery rate after a period of slow progress. This might be related to the effects of disturbances on abiotic and biotic resources, also reflecting the profound influences of slash-and-burn on community restoration. Moreover, even if the EDBMF showed slow processes of recovering species composition following disturbances, such processes were methodic to some degrees.

       

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