Integrating microbial meta-omics, isotopes and methane metabolites to connect belowground microbial processes to aboveground methane emissions in seasonally-inundated Amazonian floodplain forests
EMSL Project ID
60874
Abstract
The seasonally inundated floodplain forests of the Amazon River and its tributaries are iconic examples of ecosystems at the terrestrial-aquatic interface that are dominated by hydro-biogeochemical processes. Though the Amazon basin floodplain forests have been estimated to emit more methane (CH4) from the stems of its trees than is emitted from all Arctic wetlands combined (Pangala et al., 2017), integrated study of the controls, budget and seasonal dynamics of CH4 cycling in these great forests is lacking. This project would build on the first continuous whole-ecosystem measurements of CH4 emissions, via eddy covariance methods, from a seasonal inundated floodplain forest in the Amazon (supported by an existing DOE BER study, DE-SC0022135, entitled “Trees as Conduits for Connecting Belowground Microbial Processes to Aboveground CH4 Emissions at the Terrestrial-Aquatic Interface”).
Two puzzles challenge our understanding of Amazonian CH4 cycling: First, the mismatch between top-down estimates (from satellites or aircraft) which show a large source of CH4 to the atmosphere, and bottom-up estimates (from individual sites and soil flux measurements) which show a much smaller source or even a sink. The second puzzle is the gap in our understanding of the controls on CH4 emission and seasonal dynamics from this forested hydro-biogeochemical system.
This project will test the hypothesis that both of these puzzles are manifestations of an often-suggested but still not comprehensively-studied mechanism: the transport of significant amounts of microbially produced CH4 from lower soil depths via tree roots and stems to the atmosphere, bypassing the soil surface where most flux measurements are made, and from which most bottom-up flux budgets are constructed.
The baseline DOE BER-funded study provides key flux measurements at soil/water surfaces and tree surfaces (via flux chambers), and whole-ecosystems (via eddy covariance), and baseline microbial measurements of CH4-cycling microbial communities in soils and in trees via 16S amplicon sequencing. Critically needed but still missing from the currently funded work are the direct measures of the functional capacities and activities of CH4-cycling microbial communities in different ecosystem compartments – principally metagenomes (metaG, to elucidate functional capacity) and metatransciptomes (metaT, to reveal gene expression), and paired untargeted metabolomics (to identify CH4-related biochemical transformations as they are occuring) – that can definitively locate and identify the microbial players and their dynamics to dispositively address the two puzzles above.
With this grant we would evaluate CH4-cycling microbial communities along CH4 gradients in belowground soil profiles and in tree stems, analyze them via metaG and metaT sequencing and metabolomics (along with isotopes of CH4 soil gas) to mechanistically identify the distribution of CH4 production and consumption activity in soils and tree stems, and how these components shift between wet and dry season in seasonally inundated forests, and between a floodplain forest and a reference upland terra firme forest.
This project would bring the hydro-biogeochemistry of a critical but neglected ecotype (the great iconic flooded forests of the Amazon) into the growing global suite of biomes where the “ecosystem genomics” of critical metabolic gases such as CH4, are elucidated by integrating ecosystem processes with meta-omic measures of small scale functional drivers of those processes.
Project Details
Project type
FICUS Research
Start Date
2023-10-01
End Date
N/A
Status
Active
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members