The Science

The Amazon forest, with vast biodiversity and territorial extension, cycles more carbon and water than any other terrestrial ecosystem on the planet. However, understanding the tree species and chemical composition of this rich biodiversity and how its products can sustainably benefit humans remains a major challenge. In this study, researchers from Lawrence Berkeley National Laboratory (LBNL) present a new rapid field collection technique to characterize the composition of monoterpenes present in stem resins of 77 Protium individuals across 15 species in a primary rainforest ecosystem in the central Amazon rainforest. By normalizing the monoterpenes present in each tree sample by the most abundant monoterpene, they generated a database of monoterpene ‘fingerprints,’ which allowed comparison across individuals and species. From this analysis, nine types of monoterpene ‘fingerprint’ patterns emerged, characterized by a distinct dominant monoterpene.

The Impact

The results are consistent with a previous study that found at least five divergent copies of monoterpene synthase enzymes in Protium, and suggest that each of the nine monoterpene ‘fingerprint’ types may be determined by the presence of a distinct monoterpene synthase enzyme. A comparison of monoterpene ‘fingerprint’ between years from the same individuals showed excellent agreement, suggesting that the ‘fingerprints’ are highly sensitive to the individual/species, but show relatively low annual variability. They therefore conclude that Protium monoterpene ‘fingerprints’ show a strong dependence on species identity, but not time of collection.

This study suggests that the presented method can be used to help constrain the identity of unknown Protium species and therefore can be used as a new tool in resinous tree chemotaxonomy. By characterizing the composition of monoterpene resins among Protium species in the central Amazon, the results will contribute to future Protium studies on plant-microbe and plant-insect interactions, phylogenetic relationships and evolutionary histories, atmospheric chemistry and land-surface climate interactions, and commercial uses of resins. Finally, knowledge of the distribution of specific monoterpene ‘fingerprints’ among Protium tree species will contribute to the conservation, management, and sustainable use of tropical ecosystems.

Summary

Volatile terpenoid resins represent a diverse group of plant defense chemicals involved in defense against herbivory, abiotic stress, and communication. However, their composition in tropical forests remains poorly characterized. As a part of tree identification, the ‘smell’ of damaged trunks is widely used, but is highly subjective. Here, researchers from LBNL analyzed trunk volatile monoterpene emissions from 15 species of the genus Protium in the central Amazon. By normalizing the abundances of 28 monoterpenes, 9 monoterpene ‘fingerprint’ patterns emerged, characterized by a distinct dominant monoterpene. While four of the ‘fingerprint’ patterns were composed of multiple species, five were composed of a single species. Moreover, among individuals of the same species, six species had a single ‘fingerprint’ pattern, while nine species had two or more ‘fingerprint’’ patterns among individuals. A comparison of ‘fingerprints’ between 2015 and 2017 from 15 individuals generally showed excellent agreement, demonstrating a strong dependence on species identity, but not time of collection. The results are consistent with a previous study that found multiple divergent copies of monoterpene synthase enzymes in Protium. They conclude that the monoterpene ‘fingerprint’ database has important implications for constraining Protium species identification and phylogenetic relationships and enhancing understanding of physiological and ecological functions of resins and their potential commercial applications.

Principal Investigator

Kolby Jardine
Lawrence Berkeley National Laboratory
kjjardine@lbl.gov

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

This material is based on work supported as part of the Next-Generation Ecosystem Experiments (NGEE)–Tropics project and the Terrestrial Ecosystem Science program funded by the Office of Biological and Environmental Research, within the U.S. Department of Energy (DOE) Office of Science, through Contract No. DE-AC02-05CH11231 to Lawrence Berkeley National Laboratory. Additional funding for this research was provided by the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq).

Related Links

• NGEE–Tropics

References