At Harvard Forest's Climate Interactions with Forest Fragmentation (CLIFF) experimental site, we are using tree stem collars and belowground measurements to better understand the below-ground drivers of methane emissions from upland tree stems from clearing-to-interior gradients and across different precipitation regimes.

Please reach out to me for more information regarding this project

An extension of an NSF REU internship, continuing to investigate spatial and temporal variability of methane efflux in a controlled flooded forest in Biosphere 2

Mentor(s): Dr. Joost van Haren (Franke Honors College, University of Arizona), Jason Deleeuw (Rain Forest Research Specialist and Terrestrial Biome Manager, Biosphere 2)

Please reach out to me for more information regarding this project

See me present this research at the American Geophysical Union Conference (2023)

• Wednesday, December 13th; 8:30 AM - 12:50 PM CST

• Moscone Center, South, Poster Hall A-C

• San Francisco, California

Abstract: “Spatial and Temporal Patterns of Methane Efflux in a Controlled Flooded Forest Inside Biosphere 2 ” 

Authors: Junior Burks, Joost van Haren, Jason Deleeuw

Due to its greater radiative forcing potency compared to carbon dioxide, gaseous methane plays a key role in our climate system. Wetland ecosystems constitute a significant portion of the global methane cycle, with one major source of emissions being from annually flooded forests in the Amazon basin. Recent research has shown that tree stems can significantly contribute to the methane flux from waterlogged ecosystems (Pangala et al. 2013, 2017). However, to fully assess the influence of tree stem fluxes on flooded forest methane emissions and the global budget, we need to better understand the spatial and temporal variability of the fluxes.

In the Biosphere 2 Tropical Rainforest’s várzea, we performed controlled flooding experiments to better understand the spatial and temporal aspects of wetland methane emissions. We sought to understand patterns behind tree stem fluxes including spatial variability across the surface of a stem and temporal variability over the duration of a flood. Using manual tree stem chambers on Pterocarpus indicus and Theobroma cacao trees, and a floating diffusion/ebullition chamber, we quantified methane emissions throughout dry periods and extended floods.

Our results suggest that 1) peak stem emissions are highly variable in time between species, 2) emissions continue to increase over time without peaking, 3) stem fluxes decrease strongly with height along tree stems, 4) stem fluxes vary radially across tree stems, and 5) tree stem fluxes correlate well with sap flux rates over a 24hr diurnal period. Understanding when and where to measure tree stem emissions will help to improve the ability to quantify how significant wetland ecosystems and their trees are in the global methane and climate cycles for use in models.

References

Pangala, S. R., Enrich-Prast, A., Basso, L. S., Peixoto, R. B., Bastviken, D., Hornibrook, E. R. C., Gatti, L. V., Marotta, H., Calazans, L. S. B., Sakuragui, C. M., Bastos, W. R., Malm, O., Gloor, E., Miller, J. B., & Gauci, V. (2017). Large emissions from floodplain trees close the Amazon methane budget. Nature 552, 230–234. https://doi.org/10.1038/nature24639

Pangala, S. R., Moore, S., Hornibrook, E. R. C., & Gauci, V. (2013). Trees are major conduits for methane egress from tropical forested wetlands. New Phytologist 197, 524-531. https://doi.org/10.1111/nph.12031