- 1Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Estonia
- 2Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Estonia
- 3Department of Biological and Agricultural Engineering, University of Arkansas, USA
- 4Department of Agricultural Sciences, Environmental Soil Science, University of Helsinki, Finland
- 5Institute for Atmospheric and Earth System Research, University of Helsinki, Finland
- 6Department of Environmental Science, Policy and Management, University of California, Berkeley, USA
- 7UMR PVBMT, Université de La Réunion, 97410 Saint-Pierre, La Réunion, France
Peatland cloud forests represent one of the least studied ecosystems regarding methane (CH4) exchange despite their significance in carbon storage and the highly variable soil moisture that results from the presence of clouds in these environments. We aimed to investigate the CH4 exchange in the peat soil and tree stems of two selected tropical cloud forests on Réunion Island (one featuring Erica reunionensis and a second mix of E. reunionensis and Alsophila glaucifolia). Additionally, we explored the soil microbiology in various below- and above-ground forest compartments (soil, canopy soil, leaves, and stems) by exploring gene abundances and the microbial community structure.
In this study, we measured CH4 fluxes from peat soil and tree stems using GC-ECD and LI-COR LI-7810 analyzers, respectively. Additionally, we performed metagenomics and qPCR on selected genes involved in methanogenesis and methanotrophy in the soil and above-ground samples. Soil’s physical and chemical properties were also determined.
The peat soil found in both forests functioned as a net sink for CH4 and a source of CO2, with increased CH4 uptake occurring in soils dominated by endemic tree species E. reunionensis. Additionally, the stems of trees in the mixed forest sites acted as a weak sink for CH4. In these soils, a high abundance of NC10 bacteria (involved in n-DAMO - nitrite/nitrate-dependent anaerobic methane oxidation) was associated with the high soil nitrate (NO3-) levels, CH4 sink values, and CO2 emissions, indicating a high potential for nitrate-dependent oxidation of CH4. The ratio of mcrA (methanogenesis) to pmoA and n-DAMO (methanotrophy) genes was consistently less than 1 in the soil of both forests, whereas it exceeded 1 in the above-ground samples, including cryptogamic canopy soils and tree leaves. Metagenomic analyses revealed that soil had a high prevalence of the xoxF gene, which is associated with n-DAMO, while the above-ground compartments of both forests exhibited a high abundance of methanogenic genes (mcrA and mtr).
The peat soil of tropical cloud forests exhibited a high potential for methanotrophy, with significant CH4 consumption by n-DAMO microbes. In contrast, the above-ground components of these forests may play a notable role in methanogenesis, occurring within cryptogams and leaves, as suggested by the high abundance of mcrA and mtr genes in the leaves and canopy soil.
How to cite: Kazmi, F. A., Mander, Ü., Khanongnuch, R., Öpik, M., Ranniku, R., Soosaar, K., Masta, M., Tenhovirta, S., Kasak, K., Ah-Peng, C., and Espenberg, M.: Distinct microbial communities drive the CH4 cycles in below and above-ground compartments of tropical peatland cloud forests , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6606, https://doi.org/10.5194/egusphere-egu25-6606, 2025.
