Journal article
Seasonal changes in tree stem and soil methane fluxes along a soil moisture gradient in a subtropical Australian rainforest
Biogeochemistry, Vol.First online, pp.1-23
10/09/2026
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Abstract
Natural soil microbial methane (CH<sub>4</sub>) uptake is well documented, but uncertainty remains about uptake rates in subtropical forest and the extent to which tree stem emissions may offset the soil CH<sub>4</sub> sink. We compared seasonal CH<sub>4</sub> fluxes from trees and soils in a subtropical Australian rainforest. We conducted four campaigns to measure in situ CH<sub>4</sub> fluxes from tree stems and soils across three plots along a moisture gradient (valley floor, lower slope, and upper slope plots). Tree stem and soil CH<sub>4</sub> fluxes showed a significant positive correlation with soil moisture. Valley floor soil CH<sub>4</sub> fluxes transitioned between a CH<sub>4</sub> sink (end dry season: − 151 µmol soil m −2 d −1 ) to a source (end wet season: 830 µmol soil m −2 d −1 ). Drier soils of the slope plots acted as a net CH<sub>4</sub> sink year-round, with average soil CH<sub>4</sub> fluxes of − 135 µmol soil m −2 d −1 (lower slope) and − 156 µmol soil m −2 d −1 (upper slope). In the sloped plots, tree stems emitted negligible CH<sub>4</sub> , except for two “high-emitting” trees, featuring CH<sub>4</sub> fluxes 200 and 300-fold higher than the adjacent trees. In the valley floor at the end of the wet season, tree stem emission contributed an extra 27% to the soil CH<sub>4</sub> source, while in the slope plots, tree CH<sub>4</sub> emissions offset < 1% of soil CH<sub>4</sub> uptake. This study adds to the limited knowledge of high temporal and spatial heterogeneity of upland tree and soil CH 4 fluxes, and it highlights the importance of rainforest soils as important global CH<sub>4</sub> sink.
Details
- Title
- Seasonal changes in tree stem and soil methane fluxes along a soil moisture gradient in a subtropical Australian rainforest
- Creators
- Johannes Dittmann - Southern Cross UniversityDamien T. Maher - Southern Cross UniversityScott G. Johnston - Southern Cross UniversityAdhwaith Das - Southern Cross UniversityJames A. Padilla-Montalvo - Southern Cross UniversityAtticus E. L. Stovall - Earth System Science Interdisciplinary CenterLuke C. Jeffrey - Southern Cross University
- Publication Details
- Biogeochemistry, Vol.First online, pp.1-23
- Publisher
- Springer Nature
- Identifiers
- 991013402372102368
- Copyright
- © The Author(s) 2026
- Academic Unit
- Faculty of Science and Engineering; Graduate School; Science
- Language
- English
- Resource Type
- Journal article