Mensah Sylvanus, du Toit Ben, Seifert Thomas
Department of Forest and Wood Science, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa.
Laboratoire de Biomathématiques et d'Estimations Forestières, Université d'Abomey-Calavi, 03 BP 2819, Cotonou, Bénin.
Oecologia. 2018 Jul;187(3):783-795. doi: 10.1007/s00442-018-4144-0. Epub 2018 Apr 24.
Forest stratification plays a crucial role in light interception and plant photosynthetic activities. However, despite the increased number of studies on biodiversity-ecosystem function, we still lack information on how stratification in tropical forests modulates biodiversity effects. Moreover, there is less investigation and argument on the role of species and functional traits in forest layers. Here, we analysed from a perspective of forest layer (sub-canopy, canopy and emergent species layers), the relationship between diversity and aboveground biomass (AGB), focusing on functional diversity and dominance, and underlying mechanisms such as niche complementarity and selection. The sub-canopy layer had the highest species richness and diversity, while the emergent layer had the highest AGB. Species richness-AGB relationship was positive for each forest layer, but stronger for sub-canopy layer than for canopy and emergent layers. Total AGB was strongly correlated with functional diversity, leaf and wood traits of species in the sub-canopy and canopy layers. This suggests that sub-canopy and canopy species are major drivers of stand diversity-AGB relationship, and that resource filtering by canopy or emergent trees may not reduce the strength of diversity-AGB relationship in the sub-canopy layer. We argue that complementary resource use by sub-canopy species that supports niche complementarity, is a key mechanism driving AGB in natural forests. Selection effects are most evident in emergent species and niche complementarity effects for sub-canopy and canopy species, supporting arguments that AGB is affected by sub-canopy species' efficient use of limited resources despite competition from emergent species.
森林分层在光拦截和植物光合作用活动中起着关键作用。然而，尽管关于生物多样性与生态系统功能的研究数量有所增加，但我们仍然缺乏关于热带森林分层如何调节生物多样性效应的信息。此外，对于森林各层中物种和功能性状的作用，研究和讨论较少。在这里，我们从森林层（亚冠层、冠层和乔木层）的角度分析了多样性与地上生物量（AGB）之间的关系，重点关注功能多样性和优势度，以及生态位互补和选择等潜在机制。亚冠层具有最高的物种丰富度和多样性，而乔木层具有最高的AGB。每个森林层的物种丰富度与AGB的关系都是正相关的，但亚冠层比冠层和乔木层更强。总AGB与亚冠层和冠层物种的功能多样性、叶片和木材性状密切相关。这表明亚冠层和冠层物种是林分多样性与AGB关系的主要驱动因素，并且冠层或乔木层的资源过滤可能不会削弱亚冠层中多样性与AGB关系的强度。我们认为，亚冠层物种对资源的互补利用支持了生态位互补，这是驱动天然林AGB的关键机制。选择效应在乔木层物种中最为明显，而亚冠层和冠层物种则表现出生态位互补效应，这支持了尽管受到乔木层物种竞争，但AGB仍受亚冠层物种对有限资源的有效利用影响的观点。
