Previous studies into the production of methane in living trees suggest that trees have the potential to be a globally significant source of methane, which is an important greenhouse gas. Wood-rot inside living trees is known to be common, but the production of methane from this rotting material has not been considered in global methane budgets. Using a collaborative kit-based sampling effort, gas will be collected from living trees, dead wood, and debris, in western conifer forests and results evaluated in the context of forest management approaches that maximize carbon storage and hence limit methane production. A great deal of attention has been focused on forests and their role in mitigating the potentially catastrophic impacts of global change on the health of millions of people worldwide. For forest management to be as effective as possible at carbon capture, it is imperative that a better understanding of the fundamental dynamics of forest-climate interactions is developed. The quantification and characterization of methane emission from upland forests that will be undertaken in this project can inform climate modelers and forest managers about the potential role of tree-methane emission in carbon cycling. Beyond generating needed data, the work will fund both graduate and undergraduate research experiences. Specifically, the funds will extend the dissertation of a 4th year doctoral student and be used to facilitate undergraduate research experiences with a four-year college of higher education.
In upland, hardwood-dominated, eastern US forests, the occurrence of distinct species-level patterns in methane production potential suggests that the highest methane production rates drive substantial through-bark emission to the atmosphere. Initial flux estimates suggest that the magnitude of this methane source could be on the same order as the upland forest, soil methane sink. The extent to which this applies to forests more broadly is not known, as the physiology of tree species in eastern hardwood forests in the US may be particularly conducive to the development of substantive wood rot inside living trees. The physiology of coniferous species, however, can limit the spread of rot within living trees and so their potential to produce methane through this rot pathway could be much lower. Based on the methods used to measure methane production in eastern hardwood trees, the investigators will conduct paired field and laboratory studies in western US coniferous forests. Specifically, using a distributed, collaborative, kit-based sampling effort, gas will be collected from living trees, dead wood, and debris, in western conifer forests. In addition, wood samples will be collected across a chronosequence and placed in static chambers to assess the magnitude of methane flux. A subset of these debris samples will be subjected to microbial community analysis to relate observed methane flux rates and internal methane concentrations to microbial dynamics in living trees and downed dead wood.
