TY - JOUR
T1 - A versatile gas flux chamber reveals high tree stem CH4 emissions in Amazonian peatland
AU - van Haren, Joost
AU - Brewer, Paul E.
AU - Kurtzberg, Laura
AU - Wehr, Rachel N.
AU - Springer, Vanessa L.
AU - Espinoza, Rodil Tello
AU - Ruiz, Jorge Solignac
AU - Cadillo-Quiroz, Hinsby
N1 - Funding Information:
We acknowledge the invaluable support of Ing. Jose D. Urquiza Muñoz for hosting our teams in the Soils Laboratory of Soil Research in the Research Institute of Amazonia's Natural Resources of the National University of the Peruvian Amazon. We also wish to provide special recognition to the multiple field assistants in tree flux measurements including David Reyna Huaymacari, Franco Macedo Tafur, Miguel Fernando Campos Soria, Sergio Garcia Noriega, Daniela Buollosa Pouskel, Elda Rodriguez Insapillo, Franz Gonzales Vargas and Cpt. Isidoro Pacaya.
Funding Information:
This work was primarily supported by the Division of Environmental Biology of the National Science Foundation [grant number 1355066 to HCQ and JvH]) and the University of Arizona Honors College (student internship funding LK, RW and VS).
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2021/9/15
Y1 - 2021/9/15
N2 - Tree stems can be a major source of CH4, altering the impact forests have on atmospheric radiative forcing. In the tropics stem flux monitoring has been limited, nevertheless, available field studies have observed high variability of stem CH4 flux rates between species and individuals and over the surface of individual tree stems. To evaluate the sources of variation and controls of CH4 stem fluxes, methods supporting large sampling campaigns are needed. We designed a portable, flexible, easily installed chamber that produces replicable flux measurements across broad species diversity. The chamber creates a strong seal on a range of stem sizes and surface roughnesses and extends radially, integrating surface flux variation so that small hot spots are not missed. Working in forested Amazonian peatlands, we used this chamber to measure stem fluxes on a variety of palms and trees with stems ranging from 10 cm to 85 cm DBH, both rough and smooth barked species. We compared a non-steady state, headspace recirculation method to a steady-state flow-through method and found the flow-through method likely yields more accurate estimates for high emissions. Our novel stem flux measurements from Amazonian peatlands reveal that stem CH4 emissions of the dominant palm (M. flexuosa) contrast markedly against dominant hardwood species, with palms emitting CH4 at much higher rates (up to 84 mg-C m−2 h−1 at 0.23 m stem height) that compare to the highest published rates of tree stem emission. Flux rates from M. flexuosa demonstrated exponential decay with stem height, rates at 0.5 m were 3 to 10 times higher than at 1.4 m. This pattern underscores the importance of quantifying CH4 flux rates over the lower 2 m of stem in order to accurately quantify stem CH4 fluxes. Considering their broad distribution and high density in Amazonian peatlands, M. flexuosa stems may be a major source of atmospheric CH4.
AB - Tree stems can be a major source of CH4, altering the impact forests have on atmospheric radiative forcing. In the tropics stem flux monitoring has been limited, nevertheless, available field studies have observed high variability of stem CH4 flux rates between species and individuals and over the surface of individual tree stems. To evaluate the sources of variation and controls of CH4 stem fluxes, methods supporting large sampling campaigns are needed. We designed a portable, flexible, easily installed chamber that produces replicable flux measurements across broad species diversity. The chamber creates a strong seal on a range of stem sizes and surface roughnesses and extends radially, integrating surface flux variation so that small hot spots are not missed. Working in forested Amazonian peatlands, we used this chamber to measure stem fluxes on a variety of palms and trees with stems ranging from 10 cm to 85 cm DBH, both rough and smooth barked species. We compared a non-steady state, headspace recirculation method to a steady-state flow-through method and found the flow-through method likely yields more accurate estimates for high emissions. Our novel stem flux measurements from Amazonian peatlands reveal that stem CH4 emissions of the dominant palm (M. flexuosa) contrast markedly against dominant hardwood species, with palms emitting CH4 at much higher rates (up to 84 mg-C m−2 h−1 at 0.23 m stem height) that compare to the highest published rates of tree stem emission. Flux rates from M. flexuosa demonstrated exponential decay with stem height, rates at 0.5 m were 3 to 10 times higher than at 1.4 m. This pattern underscores the importance of quantifying CH4 flux rates over the lower 2 m of stem in order to accurately quantify stem CH4 fluxes. Considering their broad distribution and high density in Amazonian peatlands, M. flexuosa stems may be a major source of atmospheric CH4.
KW - Amazon peatlands
KW - Mauritia flexuosa
KW - Methane
KW - Stem flux
KW - Tree flux chamber
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U2 - 10.1016/j.agrformet.2021.108504
DO - 10.1016/j.agrformet.2021.108504
M3 - Article
AN - SCOPUS:85109506332
SN - 0168-1923
VL - 307
JO - Agricultural and Forest Meteorology
JF - Agricultural and Forest Meteorology
M1 - 108504
ER -