As part of the 6th call for transnational and interdisciplinary access to research infrastructures under the European ATMO ACCESS program, the project by David Beilman (University of Hawaii at Manoa, Department of Geography & Environment) has been accepted by the ATMO ACCESS evaluation panel.

Mare au Thym, Bélouve, in high Sphaignes marshes

Project title and acronym: Long-term sensitivity and resilience of montane peatland carbon on La Reunion (PeatCReu24)

Scientific background: As much as one-third of the global soil carbon pool is estimated to be held in peatland ecosystems globally, despite covering only a few percent of total land area. The unique environment and extreme high carbon density of peatlands makes their potential carbon flux to the atmosphere a global change threat under disturbance by land use, fire, and climate change. Tropical peatlands are the least studied and understood of all peatlands globally, yet can be abundant on high tropical volcanic islands, such as the Hawaiian Archipelago and la Reunion. They are ‘triple hotspots’ of biodiversity, carbon storage, and unique sedimentary archives of past ecosystem sensitivity and resilience in the peat they sequester over thousands of years.

Scientific objectives of the project: The project proposes to further investigate an important study site on La Reunion for comparison to Hawaii. The region is the Plaine ds Marsouins, where our preliminary data shows that peatlands have existed here for more than twenty thousand years. This spans the climate warming following the Last Glacial Maximum, allowing comparison of warming effects in the Pacific and Indian Ocean regions in the same tropical montane environments. The physical access work plan would center on visiting the region for a period of two weeks. The primary work would consist of three field tasks. First, we would conduct detailed surveys including mapping the peat depth via a network of soil probe locations and basal samples to better estimate of volumes and ages for carbon storage estimation. Second, we would collect rain and surface waters and plants to better characterize the water isotope variation and their imprint on leaf tissue chemistry. Third, we would identify and core the deepest and oldest part of the peatland to maximize our information and peat-core approach to long-term ecological change. The material would be transported back to Toulouse to the CRNS lab for further analysis and subsampling.

Interdisciplinarity of the project: This project is to study long-term ecosystem function in the context of the carbon cycle and the role of carbon-rich ecosystems and their storage and potential release of atmospheric carbon dioxide.

Innovation potential / Impact: The proposed work seeks to expand our preliminary findings and to further our comparison of tropical mountain forest ecosystems in the Pacific and Indian Ocean regions. The novel aspect of this work is the long-term understanding of ecosystem history and the relationship between carbon sequestration and global change drivers like climate and disturbance. The Last Glacial Maximum age of the Plaine des Marsouins peatlands, and its comparison to similar ancient landscape in Hawaii, is a first-of-its-kind comparison. Such a long-term perspective of these critical zone processes that is possible with study of these sites is rare. Finding and explicitly comparing similar sites in tropical mountain ecosystems has never been done before.

Request for access to OSU-Réunion platforms: OPAR and OZC-R

Access period: September 1-15, 2024

Administrative and logistical support: No administrative assistance is needed. Logistic assistance would be in the form of accommodation and transportation to the study site.

Availability and use of data and results: All data generated from the access would be shared with the facility and be publically available. Our approach to data repositories is to use more than one to ensure that data is available to all interested parties.

Distribution of results: The ongoing collaboration aims to publish a number of papers and conference presentations about these unique ecosystems and their comparison across La Reunion and Hawaii. These have already started.

Initial results from a previous mission (ANR Atmo-plastic) show that the environmental archive at Plateau de Thym dates back more than 20,000 years. This would retrace the last climatic warming followed by the last glaciation (Late Glacial Maximum), enabling a comparison of ecological history and climatic changes between the Indian and Pacific Oceans. This comparison between Reunion Island and Hawaii is a new opportunity to better understand the critical zone and ecosystem dynamics over the long term.