Partitioning Tree Methane Emissions

The role of plants in the global methane (CH4) cycle remains poorly understood. Plants can emit CH4 from aerobic methane production (AMP), microbial methanogenesis within plants (MMP), and the export soil methane (SM) via plant tissues. These plants-associated CH4 emissions may be quantitatively significant (15-65% of all natural CH4 emissions) but remain poorly
constrained. So far, field studies have only quantified the sum of all these plant-atmosphere CH4 fluxes, limiting the degree to which each process can be mathematically described and incorporated into CH4 budgets and models.

In PaTreME, we aim to (a) develop a method to separately quantify AMP, MMP, and SM emissions from plants based on the CH4 isotope values (δ13C, δ2H, and Δ14C) and methanol co-emissions (MeOH:CH4), and (b) apply this method to methane emissions from boreal forest trees at the SMEAR II research site in Southern Finland.

To reach these goals, will require (1) adapting stem and shoot enclosure chambers to collect CH4 for offline analysis; (2) identifying characteristic CH4 isotope and MeOH:CH4 values of AMP, MMP, and SM; (3) measuring isotope and MeOH:CH4 values of plant CH4 emissions at SMEAR II, and (4) developing a Bayesian petitioning model for plant CH4 emissions.