Fine-scale processes shape ecosystem service provision by an Amazonian hyperdominant tree species

Evert Thomas,Chris Kettle,Rachel Atkinson

doi:10.1038/s41598-018-29886-6

Evert Thomas, Chris Kettle + Show 1 more

Open Access

https://doi.org/10.1038/s41598-018-29886-6

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Abstract

Conspecific distance and density-dependence is a key driver of tree diversity in natural forests, but the extent to which this process may influence ecosystem service provision is largely unknown. Drawing on a dataset of >135,000 trees from the Peruvian Amazon, we assessed its manifestation in biomass accumulation and seed production of Brazil nut (Bertholletia excelsa) which plays a keystone role in carbon sequestration and NTFP harvesting in Amazonia. For the first time, we find both negative and positive effects of conspecific proximity on seed production and above ground biomass at small and large nearest neighbour distances, respectively. Plausible explanations for negative effects at small distances are fine-scale genetic structuring and competition for shared resources, whereas positive effects at large distances are likely due to increasing pollen limitation and suboptimal growth conditions. Finally, findings suggest that most field plots in Amazonia used for estimating carbon storage are too small to account for distance and density-dependent effects and hence may be inadequate for measuring species-centric ecosystem services.

Highlights

The importance of Amazon forests for the provision of ecosystem goods and services to human society is well recognized
Our findings show that the precision and accuracy of sample plots to predict expected area-based seed production and above ground biomass (AGB) increase asymptotically with plot size, and suggest that most currently used Amazonian plots may underestimate the ecosystem services of individual tree species
Many Amazonian hyperdominant tree species share similar spatial distributions and reproductive traits as the Brazil nut, and play dominant roles in the forest’s ecosystem service provision[1,2,90]

Summary

Introduction

The importance of Amazon forests for the provision of ecosystem goods and services to human society is well recognized. Plot-based assessments of ecosystem services related to standing biomass and fruit production of individual tree species are likely to be affected by scale effects. This is so because most forest plots are less than one hectare[1] while most tree species in Amazonia, including many hyperdominant species, occur at densities below one tree per hectare[2]. By contrast, seed production is generally expected to be higher in trees that grow closer to conspecific neighbours or in areas with higher conspecific density owing to higher pollination distances and increased selfing rates in more isolated trees[21] Such positive DDD fecundity has been described for numerous tree species around the world[25,26,27] and may be manifested in predominantly cross-pollinated (self-incompatible) species which make up the large majority of tropical tree species[28]. Crosses between individuals with high kinship result in elevated biparental inbreeding which may lead to an increase in seed abortion rates[33], and lower the seed set[34]

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