Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH 43210, USA.
BMC Ecol. 2012 Mar 19;12:3. doi: 10.1186/1472-6785-12-3.
Disturbance is an important process structuring ecosystems worldwide and has long been thought to be a significant driver of diversity and dynamics. In forests, most studies of disturbance have focused on large-scale disturbance such as hurricanes or tree-falls. However, smaller sub-canopy disturbances could also have significant impacts on community structure. One such sub-canopy disturbance in tropical forests is abscising leaves of large arborescent palm (Arececeae) trees. These leaves can weigh up to 15 kg and cause physical damage and mortality to juvenile plants. Previous studies examining this question suffered from the use of static data at small spatial scales. Here we use data from a large permanent forest plot combined with dynamic data on the survival and growth of > 66,000 individuals over a seven-year period to address whether falling palm fronds do impact neighboring seedling and sapling communities, or whether there is an interaction between the palms and peccaries rooting for fallen palm fruit in the same area as falling leaves. We tested the wider generalisation of these hypotheses by comparing seedling and sapling survival under fruiting and non-fruiting trees in another family, the Myristicaceae.
We found a spatially-restricted but significant effect of large arborescent fruiting palms on the spatial structure, population dynamics and species diversity of neighbouring sapling and seedling communities. However, these effects were not found around slightly smaller non-fruiting palm trees, suggesting it is seed predators such as peccaries rather than falling leaves that impact on the communities around palm trees. Conversely, this hypothesis was not supported in data from other edible species, such as those in the family Myristicaceae.
Given the abundance of arborescent palm trees in Amazonian forests, it is reasonable to conclude that their presence does have a significant, if spatially-restricted, impact on juvenile plants, most likely on the survival and growth of seedlings and saplings damaged by foraging peccaries. Given the abundance of fruit produced by each palm, the widespread effects of these small-scale disturbances appear, over long time-scales, to cause directional changes in community structure at larger scales.
干扰是全球生态系统结构的重要过程，长期以来一直被认为是多样性和动态变化的重要驱动因素。在森林中，大多数关于干扰的研究都集中在大规模干扰上，如飓风或树木倒伏。然而，较小的林冠下干扰也可能对群落结构产生重大影响。在热带森林中，一种这样的林冠下干扰是大型乔木棕榈树（Arececeae）的落叶。这些叶子的重量可达 15 公斤，会对幼树造成物理伤害和死亡。以前研究这个问题的研究受到小空间尺度静态数据的限制。在这里，我们使用来自一个大型永久性森林样地的数据，结合 7 年来超过 66000 个个体的生存和生长动态数据，来确定落叶棕榈叶是否会影响邻近的幼苗和幼树群落，或者棕榈树和以落叶为食的野猪是否会在同一区域对落果产生相互作用。我们通过比较另一个科——肉豆蔻科（Myristicaceae）中结果和非结果树木下幼苗和幼树的生存情况，来检验这些假设的更广泛的普遍性。
我们发现，大型乔木结果棕榈对邻近幼树和幼苗群落的空间结构、种群动态和物种多样性有空间限制但显著的影响。然而，在稍小的非结果棕榈树周围并没有发现这些影响，这表明是食果动物如野猪而不是落叶对棕榈树周围的群落产生了影响。相反，这个假设在来自其他可食用物种的数据中，如肉豆蔻科，并没有得到支持。
鉴于亚马逊森林中乔木棕榈树的丰富程度，可以合理地得出结论，它们的存在确实对幼年植物有显著的影响，即使这种影响是空间限制的，最有可能是对觅食野猪造成伤害的幼苗和幼树的生存和生长产生影响。鉴于每棵棕榈树产生的果实数量众多，这些小规模干扰的广泛影响在长时间尺度上似乎会导致更大规模群落结构的定向变化。
