Abstract
Increasing evidence is available for a positive effect of biodiversity on ecosystem productivity and standing biomass, also in highly diverse systems as tropical forests. Biodiversity conservation could therefore be a critical aspect of climate mitigation policies. There is, however, limited understanding of the role of individual species for this relationship, which could aid in focusing conservation efforts and forest management planning. This study characterizes the functional specialization and redundancy for 95% of all tree species (basal area weighted percentage) in a diverse tropical forest in the central Congo Basin and relates this to species' abundance, contribution to aboveground carbon, and maximum size. Functional characterization is based on a set of traits related to resource acquisition (wood density, specific leaf area, leaf carbon, nitrogen and phosphorus content, and leaf stable carbon isotope composition). We show that within both mixed and monodominant tropical forest ecosystems, the highest functional specialization and lowest functional redundancy are solely found in rare tree species and significantly more in rare species holding large‐sized individuals. Rare species cover the entire range of low and high functional redundancy, contributing both unique and redundant functions. Loss of species supporting functional redundancy could be buffered by other species in the community, including more abundant species. This is not the case for species supporting high functional specialization and low functional redundancy, which would need specific conservation attention. In terms of tropical forest management planning, we argue that specific conservation of large‐sized trees is imperative for long‐term maintenance of ecosystem functioning.
Highlights
Tropical forests host an enormous diversity of tree species (Slik et al, 2015) and are an important component of the global carbon balance (Pan et al, 2011)
| 4351 the community? In terms of planning for forest carbon mitigation and biodiversity conservation, identifying if a potential relationship exists will either allow for an integrated forest management planning or highlight the need for parallel tactics in terms of management for carbon mitigation and management for biodiversity conservation. (c) Do the relationships assessed in the first two research questions vary in tropical forest communities with varying environmental filtering? That is, will similar relationships between species functional importance and abundance or contribution to carbon persist within a narrower functional space? We investigate two old‐growth forest systems with a different dominance structure in the central Congo Basin: a mixed species forest and a monodominant forest dominated by Gilbertiodendron dewevrei (De Wild.) J
We conclude that high functional specialization and low redundancy are supported by a fraction of the rare species in the tree community, in a high proportion of rare species holding large‐sized individuals
Summary
Tropical forests host an enormous diversity of tree species (Slik et al, 2015) and are an important component of the global carbon balance (Pan et al, 2011). This functional assessment was made using functional traits related to resource acquisition, as complementarity of trait values therein could inform us on a positive influence on ecosystem productivity. A recent study in a tropical forest in French Guiana (Leitão et al, 2016; Mouillot, Bellwood, et al, 2013) shows rare species supporting the most distinct combinations of traits, with low redundancy Investigating if these results hold in a different tropical forest in terms of species composition, forest structure, and biogeographical conditions is important to provide more insight for the need for biodiversity conservation for ecosystem functioning. The monodominant forest studied has lower species and functional diversity than the adjacent mixed forest, showing a narrower functional niche space (Kearsley et al, 2017)
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