EGU22-11693
https://doi.org/10.5194/egusphere-egu22-11693
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Tropical forest CH4 budget: the importance of local hotspots

Hella van Asperen1,2, Thorsten Warneke1, Alessandro De Araújo3,4, Bruce Forsberg5, Sávio Ferreira6, João Alves-Oliveira7, Leonardo Ramos de Oliveira3, Thiago de Lima Xavier3, Marta Sá3, Paulo Teixeira3, Elaine Pires6, Veber Moura3, Shujiro Komiya2, Santiago Botia2, Sam Jones2, Jost Lavrič2,8, Susan Trumbore2, and Justus Notholt1
Hella van Asperen et al.
  • 1University of Bremen, Institute of Environmental Physics, Remote Sensing, Bremen, Germany
  • 2Max Planck Institute for Biogeochemistry, Jena, Germany
  • 3Programa de Grande Escala da Biosfera-Atmosfera na Amazônia (LBA), Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, Brazil
  • 4Brazilian Agricultural Research Corporation (EMBRAPA) , Embrapa Amazônia Oriental, Belém, Brazil
  • 5Coordenação de Dinâmica Ambiental (CODAM), Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, Brazil, (currently at Vermont Agency of Natural Resources, Vermont-USA)
  • 6Coordination of Environmental Dynamics (CODAM), National Institute for Research in the Amazon (INPA)
  • 7Coordenação de Pesquisas em Entomologia (CPEN), Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, Brazil
  • 8ACOEM (France): Melbourne, AU

Methane (CH4) is one of the most important anthropogenic greenhouse gases. Despite its importance, natural sources of methane, such as tropical wetlands and termites, are still not well understood and a large source of uncertainty in the tropical CH4 budget. The Amazon rainforest is a key region for the (global) CH4 budget but, due to its remote location, local CH4 concentration and flux measurements are still rare.

Fieldsite ZF2 (60 km NW of Manaus, Brazil) is located in pristine tropical rain forest. At this fieldsite, a Spectronus FTIR-analyzer (measuring CO2, CO, CH4, N2O & δ13CO2) was installed at the foot of the K34 tower, set up to measure different heights above and below the canopy continuously. In addition, by use of a Los Gatos portable analyzer (measuring CO2 & CH4), additional semi-continuous concentration measurements were performed at the valley tower (studying the nighttime build up of valley CH4), above the igarapé  (capturing the CH4 ebullition bubbles leaving the water surface), and on the plateau (studying the spatial horizontal heterogeneity of CH4 concentrations within the canopy). Furthermore, the portable analyzer was used for soil, water, termite mound, and termites flux measurements.

By combining tower and flux chamber measurements, the role and magnitude of different ecosystem sources could be assessed. We observed that, while soils in the valley are a small source of CH4 (0.1 to 0.2 nmol CH4 m-2 s-1), overall the soils of this ecosystem are expected to be a net CH4 sink (-0.3 to -0.5 nmol m-2 s-1 ). Estimated total ecosystem CH4 flux, based on nighttime concentration analyses of the tower data, indicate that the ecosystem is a net CH4 source (~1 to 2 nmol CH4 m-2 s-1). We propose that the net CH4 emission of the ecosystem is driven by local emitting hotspots, such as the valley stream and standing water, termites and termite mounds (~1 nmol CH4 m-2 s-1), anoxic soil spots and decaying dead wood.

 

How to cite: van Asperen, H., Warneke, T., De Araújo, A., Forsberg, B., Ferreira, S., Alves-Oliveira, J., Ramos de Oliveira, L., de Lima Xavier, T., Sá, M., Teixeira, P., Pires, E., Moura, V., Komiya, S., Botia, S., Jones, S., Lavrič, J., Trumbore, S., and Notholt, J.: Tropical forest CH4 budget: the importance of local hotspots, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11693, https://doi.org/10.5194/egusphere-egu22-11693, 2022.

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