About This Project

Trees play a vital role in sequestering atmospheric carbon. Barks contain diverse microbes that mediate further climate functions by removing multiple greenhouse gases, including hydrogen and methane. Identifying and promoting trees hosting these microbes offers a unique solution to combat climate change. This project integrates substantial field measurements, lab assays, and metagenomics of boreal to tropical upland forests, to provide the first estimates of this hitherto unrecognized process.

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Motivating Factor

Atmospheric methane (CH₄) removal is critical to limit global warming. Trees have emerged as an unexpected yet promising mediator. Reports show numerous bacteria capable of CH₄ oxidation reside in bark (caulosphere)^1,2,3. The caulosphere communities also consume other climate-active gases like hydrogen and carbon monoxide (H₂, CO)¹ both of which affect the atmospheric lifetime of CH₄. As the global cumulative surface area of tree bark is comparable to the soils of terrestrial Earth³, caulosphere microbes may cryptically regulate global biogeochemical and atmospheric CH₄ cycles. Forestry management promoting trees hosting these microbes may enable simultaneous removal of multiple greenhouse gases (GHG) in addition to photosynthesis carbon dioxide uptake. Currently, the function of tree microbial communities of upland forests remains poorly understood⁴. Determining the magnitude of these processes is crucial to addressing CH₄ removal, carbon abatement and reforestation strategies.

Specific Bottleneck

Upland forests account for 80% of all trees on Earth and are important locations for (re)forestry projects. Despite our recent findings on caulosphere H₂, CO, and CH₄ oxidation in subtropical lowland forests¹, data from upland forests and across latitudinal biomes are lacking. Variability across species remain unexplored, limiting our ability to generalize results, determine the caulosphere’s role in global biogeochemical cycles, and strategically plant or promote trees most effective in stripping GHGs. Currently, CH₄ budgets and Earth system models exclude bark-associated GHG processes⁵, likely greatly underestimating forests’ net climatic benefits. Furthermore, no standardized method exists for caulosphere microbial process measurements, scaling and analysis, and metagenomics are costly and specialized. Integrating sequencing, field, and lab measurements of upland forest caulosphere could fill these gaps but is hindered by resource limitations, and requires strategic funding.

Actionable Goals

This multidisciplinary, PhD-supported research integrates field measurements, lab assays, and metagenomic sequencing spanning boreal to (sub)tropical upland tree stems. By determining the contributions of caulosphere-associated microbes to GHG cycling, this research seeks to pioneer forest-based solutions for climate mitigation strategies and reshape our understanding of forests' roles in atmospheric CH₄ regulation. Actionable goals are: (1) In situ stem flux surveys of CH₄, H₂, and CO enabling quantification of fluxes at the tree and forest scale; (2) Complimentary lab-validation microcosm assays quantifying bark microbial CH₄, H₂, and CO oxidation across Q₁₀ temperature treatments; (3) Caulosphere metagenomic sequencing and cell quantification to identify key responsible microbial species; (4) Physiochemical characterization of bark features and site conditions that promote caulosphere GHG uptake; and (5) Standardizing protocols for caulosphere microbiome and stem flux scaling.