BG3.32 | Forest methane (CH4) and nitrous oxide (N2O) cycles
Forest methane (CH4) and nitrous oxide (N2O) cycles
Co-organized by SSS9
Convener: Katerina Machacova | Co-conveners: Laëtitia Brechet, Sylvia Toet, Josep Barba
| Thu, 18 Apr, 10:45–12:30 (CEST)
Room N1
Posters on site
| Attendance Wed, 17 Apr, 10:45–12:30 (CEST) | Display Wed, 17 Apr, 08:30–12:30
Hall X1
Orals |
Thu, 10:45
Wed, 10:45
Methane (CH4) and nitrous oxide (N2O) are among the most important greenhouse gases (GHG) after carbon dioxide (CO2) in accelerating global warming and deserve special attention as their concentrations increase. Forest ecosystems play an important role in the exchange of GHGs with the atmosphere. It has been shown that not only soils but also trees play a significant role in the net exchange of CH4 and N2O in forests. Trees can contribute to ecosystem exchange by uptaking and transporting soil-produced CH4 and N2O to the atmosphere, by in situ production and consumption of both gases in plant tissues, and by modifying carbon and nitrogen turnover in adjacent soils. However, the contribution of these individual processes to the net ecosystem GHG exchange is still unclear and appears to depend on many aspects such as tree species, forest ecosystem type, environmental parameters and seasonal dynamics. Soil - vegetation - atmosphere interactions play a crucial role in controlling the global budget of these gases.

This session aims to bring together scientists working on CH4 and N2O cycles in forest ecosystems across different climatic and hydrological ranges and scales, which is crucial for improving our understanding of CH4 and N2O exchange in forest ecosystems. We welcome contributions on production and consumption processes and mechanisms in soils and plant tissues, as well as on gas transport processes in the soil - tree - atmosphere continuum. Gas flux measurements from forest soils, cryptogams, tree stems, leaves or canopies measured with chamber systems, or integrated ecosystem approaches (flux tower with Eddy covariance, satellite or modelling) would be very appreciated.

Orals: Thu, 18 Apr | Room N1

Chairpersons: Katerina Machacova, Laëtitia Brechet
On-site presentation
Ülo Mander, Reti Ranniku, Thomas Schindler, Mikk Espenberg, Jordi Escuer-Gatius, Katerina Machacova, Jaan Pärn, Mohit Masta, Fahad Ali Kazmi, Lulie Melling, Lizardo Manuel Fachin Malaverri, Mari Pihlatie, Laura Kuusemets, Kuno Kasak, and Kaido Soosaar

Forests cover about 4 billion ha globally. They are important regulators of carbon dioxide (CO2) fluxes, whereas the comprehensive understanding of their overall greenhouse gas (GHG) budgets, especially for methane (CH4) and nitrous oxide (N2O), are still largely unknown.

Wetland forest soils are commonly recognized as emitters of CH4, whereas upland forest soils tend to consume CH4. However, several studies demonstrate that trees can emit a large amount of CH4 especially from tree stems and substantial amounts also from canopies through poorly studied and partly unidentified aerobic processes. Moreover, tree stems can have substantial concentrations of CH4 inside, which can originate from soil or be produced by methanogens within the wood, while canopy CH4 emissions are mostly abiotic and driven by light and temperature. Thus, forest vegetation can be a significant CH4 source.

Various soil microbiological, chemical and physical properties influence N2O fluxes in forests. In general, N2O emissions from tropical wetland forest soils are significantly higher than those from tropical upland forests, temperate and boreal forests. High nitrogen (N) availability, coupled with high moisture content, makes tropical peatland soils especially likely to emit N2O. Similarly, forests on drained N-rich peatland soils in temperate and boreal areas can be significant N2O sources. In temperate zone, a considerable part of such emissions appears in winter.

Understanding spatial and temporal dynamics of GHG emissions is crucial for adequate modelling and mitigation of emissions in forests. In comparison with CO2 fluxes, which are clearly temperature dependent, temporal and spatial variation of soil, tree stem and canopy CH4 and N2O emissions is more complex and poorly studied. Soil N2O emissions in wetland and upland forests are mainly determined by soil moisture (soil oxygen concentration), and N2O shows bell-shaped (unimodal) dependence on soil water content. In the wet periods, stem flux of CH4 can be the main source for ecosystem exchange, whereas in the dry periods, emission from canopy adds to the total fluxes from soil and stems. N2O fluxes from the soil and stems are normally low during the dry periods and peak during the wet periods and the freeze-thaw cycles.

Only a few examples are available on ecosystem-level CH4 and N2O budgets (fluxes from the soil, tree stems and shoots + eddy covariance (EC) measurements above the canopy). Nevertheless, estimation of the GHG balance in different forest ecosystems under various environmental conditions is essential for understanding their impact on the Earth’s climate.

In this presentation, we will bring results from ecosystem-level CH4 and N2O flux studies in forests growing on both organic and mineral soils in temperate and tropical zones.

How to cite: Mander, Ü., Ranniku, R., Schindler, T., Espenberg, M., Escuer-Gatius, J., Machacova, K., Pärn, J., Masta, M., Kazmi, F. A., Melling, L., Fachin Malaverri, L. M., Pihlatie, M., Kuusemets, L., Kasak, K., and Soosaar, K.: Hot spots and hot moments of methane and nitrous oxide fluxes in forests: from soil to ecosystem, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3653,, 2024.

(Hemi)boreal forests
On-site presentation
Mari Pihlatie, Salla Tenhovirta, Lukas Kohl, and Markuu Koskinen

Release of CH4 from shoots remains the least understood and most enigmatic process of tree-mediated CH4 fluxes. While stem emissions of trees derive from transported or local, biotic pathways, CH4 emissions from shoots likely originate dominantly from abiotic, aerobic production within the canopies. The estimates of the global source strength of aerobic CH4 emissions suffer from large uncertainties, due to insufficient understanding of the source processes.

In this contribution, we show the environmental drivers, temporal patterns, and physiological determinants of the aerobic CH4 emissions from the shoots of Scots pines and discuss the contribution of aerobic canopy emissions to the boreal forest CH4 cycles. We present shoot-level CH4 fluxes from saplings and mature Scots pine trees, measured in various settings, outdoors and in the greenhouse. We used chamber enclosure methods with online greenhouse gas analysers in both manual and automated measurement settings. For the automated measurements we built a custom measurement system that allowed continuous measurements of greenhouse gas fluxes.

The results from CH4 flux measurements under different light sources indicate that aerobic CH4 emissions are to the most part determined by the intensity and spectral composition of light, and that the emissions are most prominent under direct solar radiation. Hence, the diurnal variations exhibited by these emissions are associated with the diurnal cycle of sunlight, but also vary depending on the cloud conditions. By exposing Scots pine saplings to drought, we further distinguished that the light-driven CH4 emissions from shoots are not a byproduct of photosynthesis-related biochemical reactions. Rather, these emissions result from abiotic thermal and photodegradation of plant compounds.

In ambient conditions, we show median aerobic CH4 emissions of 5.41 ng CH4 g-1 DW h-1under direct sunlight and 2.52 ng CH4 g-1 DW h-1 during variable cloudiness. These emissions are 1-2 % of the emission factor used in most of the global upscale estimates of aerobic CH4 emissions from vegetation. Therefore, Scots pine canopies in boreal climates are likely a CH4 source of only minor importance on a global scale. These emissions may, however, decrease the sink strength of the boreal upland forest soils: our conservative estimate is that the canopy emissions of CH4 may decrease this soil sink strength by 2.1 – 4.6 %. This estimate may yet underestimate the significance of canopy fluxes on the ecosystem scale due to the high spatiotemporal variation of both the canopy CH4 emissions and the CH4 uptake rates of boreal upland soils. To further refine the estimates of the source strength of aerobic CH4 emissions of tree canopies it is, therefore, important to gain more data of shoot-level CH4 fluxes from field measurements.

How to cite: Pihlatie, M., Tenhovirta, S., Kohl, L., and Koskinen, M.: Resolving the aerobic methane emissions from Scots pine shoots, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22027,, 2024.

Virtual presentation
Marcus Klaus, Mats Öquist, and Kateřina Macháčová

The cycling of greenhouse gases in forest ecosystems is significantly influenced by tree stems. Yet, little is known about the variability and drivers of stem-atmosphere greenhouse gas fluxes, especially in managed boreal riparian ecosystems where environmental conditions vary substantially at small spatial scales and throughout the year. Here, we report magnitudes and drivers of tree stem-atmosphere fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in a riparian buffer zone of a Swedish boreal forest that has been subject to recent forest clearcutting and historic ditching. For two full years, we conducted CO2 and CH4 flux chamber measurements on a monthly basis in 14 spruce trees (Picea abies) and 14 birch trees (Betula pendula) that grew between one and fifteen meters from a headwater stream. We also performed N2O flux measurements during three occasions. All trees were net emitters of CO2 and CH4 over the majority of the year, while N2O fluxes were close to zero. CO2 fluxes correlated strongly and positively with air temperature and followed distinct seasonal cycles peaking in summer. CH4 fluxes correlated modestly with air temperature and solar radiation and peaked in late winter and summer. Trees with larger stem diameter released more CO2 and less CH4, and trees that were nearer the stream released more CO2 and CH4. The CO2 and CH4 fluxes did not differ between spruce and birch in general, but correlations of CO2 fluxes with stem diameter and distance to stream differed between the tree species. The absence of distinct vertical trends in the CO2 and CH4 fluxes along the stems and their lack of correlation with groundwater levels and groundwater greenhouse gas concentrations point to tree internal production as the primary source of the tree stem gas emissions. Upscaled to the ecosystem, the tree stem CO2, CH4 and N2O emissions represented 52% of the forest floor CO2 emissions and 2.5% and 11.3% of the forest floor CHand N2O uptake, respectively, during the snow-free season. The snow cover season contributed 15% and 35% to annual tree stem CO2 and CH4 emissions, respectively. In contrast to other riparian zone studies, the stem gas fluxes in our study generally exhibited characteristics of an upland rather than a wetland ecosystem, likely because of historical ditching and subsequent groundwater level declines.

How to cite: Klaus, M., Öquist, M., and Macháčová, K.: Tree stem-atmosphere greenhouse gas fluxes in a boreal riparian forest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6221,, 2024.

On-site presentation
Reti Ranniku, Joosep Truupõld, Mikk Espenberg, Jordi Escuer-Gatius, Fahad Ali Kazmi, Ülo Mander, and Kaido Soosaar

Tree stems are known to emit greenhouse gases CH4, CO2 and N2O to the atmosphere but the processes and drivers behind these fluxes are still contested. Soil water is taken up by tree roots and moves up the xylem due to a negative pressure gradient caused by transpiration through the leaves. Consequently, dissolved gases in the soil water move up the stem and are potentially diffused to the atmosphere through the bark. Periods of soil freeze-thaw in the spring are crucial hot-moments of GHG release from the soil, as well as stems. As birch trees go through a sap running period between the thawing of the soil and bud break, they provide an opportunity to study stem GHG fluxes during the peak time of emissions, together with the concentrations of dissolved gases in the birch sap.

We quantified the fluxes of CH4, CO2 and N2O from Downy birch (Betula pubescens), as well as Norway spruce (Picea abies) for comparison, in a temperate nutrient-rich drained peatland forest in April and May 2023. In addition, we studied the relationship between birch stem fluxes and dissolved gas concentrations inside the xylem sap. Stem fluxes were determined using static chambers attached to the tree stems and automatic LI-COR gas analysers. Dissolved gas samples were extracted from the collected birch sap and soil water after water-atmosphere equilibration, and were analysed in the lab using gas-chromatography. In addition, we analysed the relationships between the chemical and microbiological composition of the soil and soil and stem GHG fluxes.

Birch stem CH4, CO2 and N2O fluxes peaked in the end of April, following the the temporal trend of soil and air temperature, with higher fluxes during warmer days, likely related to increased microbial activity in the soil. Dissolved CH4 concentrations in the birch sap peaked with a delay in relation to peak stem emissions, indicating that xylem sap flow rate needs to be studied to comprehend the water dynamics inside the stem. Relationships between stem fluxes and dissolved gas concentrations were strongest at the bottom part of the tree. A more detailed analysis together with examination of the underlying soil chemistry and microbiology will be presented to further explain the processes behind soil and tree stem GHG flux dynamics.

How to cite: Ranniku, R., Truupõld, J., Espenberg, M., Escuer-Gatius, J., Ali Kazmi, F., Mander, Ü., and Soosaar, K.: Greenhouse gas fluxes from Downy Birch stems during the spring sap-run period and their dependence on dissolved gas concentrations in xylem sap, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14147,, 2024.

Temperate forests (with overlap to tropical forests)
On-site presentation
Natalia Kowalska, Georg Jocher, Adam Bednařík, Hannes Warlo, Kaido Soosaar, and Katerina Macháčová

Floodplain forests play an important role in the exchange of methane (CH4) with the 
atmosphere. However, due to climate change and anthropogenic activities, main factors driving 
this exchange, such as ground water table and soil temperature, are constantly changing. The 
studied floodplain forest in Lanžhot, Czech Republic, represents nowadays relatively dry 
The main aims of our study were to quantify the CH4 emission on the floodplain forest 
ecosystem level using the eddy covariance (EC) method, with special emphasis on 
environmental conditions, turbulence development and footprint, as well as to probe all 
potential CH4 sinks and sources within the studied ecosystem for arriving at a complete CH4
budget. The ecosystem-scale CH4 fluxes were analysed with regards to the CH4 emissions of 
water bodies within the EC footprint. CH4 fluxes from a stream located within the footprint of 
the EC tower were measured using floating chambers and bubble traps. Studies were 
complemented by the analysis of the contribution of trees to the CH4 exchange. For this 
purpose, stem chambers measured CH4 fluxes on hornbeam trees, one of the main tree species 
at the study site and in Central Europe. Additionally, CH4 fluxes from the soil were included in 
the analysis to capture all potential CH4 sources and sinks within the studied ecosystem.
We initially hypothesized that ecosystem-scale CH4 exchange will be negligible. Our results
showed, however, that the whole ecosystem is a small but constant CH4 source as we observed 
an average emission flux of 11.7 mg CH4 m-2
day-1 over the period June to December 2021. In addition, we observed variability of the CH4 fluxes in relation to the wind direction and to u*
(friction velocity, indicator for turbulence development). Further analysis shall answer on the 
question if more water bodies within a particular wind sectors means higher fluxes above the 
canopy and if higher turbulence is correlated with higher CH4 fluxes above canopy as hotspot 
emissions are better mixed up. The probed stream was a substantial source of CH4 with average
CH4 fluxes of 260 ± 107 mg CH4 m-2 day-1, respectively, over the period from April to 
December 2021. Ebullition was the dominant pathway of CH4 release throughout the whole 
monitored time period. Results from the stem and soil CH4 flux measurements identified 
hornbeam stems and soil as net sinks for CH4 (-0.025 and -0.999 mg CH4 m-2
day-1, respectively). Finally, after putting all pieces together we will arrive at a holistic view of CH4
dynamics within the studied floodplain forest ecosystem with the potential of transfer of 
knowledge to ecosystem of similar kind elsewhere.

How to cite: Kowalska, N., Jocher, G., Bednařík, A., Warlo, H., Soosaar, K., and Macháčová, K.: Ecosystem-scale floodplain forest methane exchange, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7519,, 2024.

On-site presentation
Alice Fraser-McDonald, Carl Boardman, Toni Gladding, Stephen Burnley, and Vincent Gauci

Many national governments, organisations and environmental groups have pledged to plant trees in an effort to increase carbon sequestration and mitigate climate change. Tree planting is commonly used as a restoration strategy for former landfill sites, and it is likely that many urban and urban-fringe areas, including closed landfills, will continue to be prioritised for tree planting in the coming years. Trees growing in natural and managed environments have the capacity to act as conduits for the transport of methane (CH4) produced belowground to the atmosphere. This process has also been observed in natural ecosystems for nitrous oxide (N2O) and we examined whether trees growing on closed landfills also mediate N2O emissions to the atmosphere. We investigated whether trees on a closed UK landfill site emitted more N2O than those on a comparable natural site. Measurements were made from stem and soil surfaces over a four-month period using flux chambers and Gas Chromatography. Results were then scaled up and the contributions of N2O stem fluxes to the total surface fluxes in different environments were compared. Analyses showed that stem and soil N2O fluxes from landfill were larger than from trees on the comparable non-landfill site. Tree stem N2O emissions on the former landfill also showed seasonal patterns and decreased with higher sampling positions above ground level. Findings indicated that tree stem N2O emissions accounted for less than 1% of the estimated total landfill surface flux, which was comparable to findings from a mesocosm study, but lower than estimates of the total N2O ecosystem flux in dry and flooded boreal forests (8% and 18%, respectively). Overall, this investigation suggested that trees planted on closed landfill sites may result in additional N2O emissions to the atmosphere, although the tree stem contribution to the total surface flux on the former landfill was a lower magnitude than that of fluxes previously reported from natural forested ecosystems.

How to cite: Fraser-McDonald, A., Boardman, C., Gladding, T., Burnley, S., and Gauci, V.: Nitrous oxide (N2O) emissions from a forested closed landfill site, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1443,, 2024.

On-site presentation
Carla Gomez, Sunitha Pangala, David Gowing, Karen Olsson-Francis, Susan Page, and Vincent Gauci

The contribution of trees to the wetland methane (CH4) budget remains highly uncertain. The water table level is an essential driver for stem CH4 emissions, which vary across seasons and soil hydrological conditions. Exceptionally dry conditions are increasingly affecting forests because of climate change, and wetland trees can potentially switch from CH4 sources to sinks. CH4 production and oxidation potentially occur in the oxic/anoxic microsites within wetland tree stems, as in soil, balancing the net stem CH4 emissions to the atmosphere. Yet, the microbial ecology behind these processes is still vastly unexplored, and understanding the role of microbial ecology is essential to predict stem CH4 emission patterns.

Our study focused on characterising stem CH4 fluxes using semi-rigid static chambers and assessing CH4 oxidation and production activities through gas-enriched incubations in two forested wetland ecosystems: a temperate wetland in Flitwick Moor (UK) and tropical peat swamp forests in the Sebangau Forest (Kalimantan, Indonesia), both experiencing lower water table levels than previous years during the same period. Targeted tree species were measured at multiple height intervals and were Alnus glutinosa and Betula pubescens in Flitwick Moor and Shorea balangeran and Xylopia fusca in the Sebangau Forest, the same tree species that were investigated in earlier studies at these sites. DNA analysis from bark, wood, and soil involved two-step PCR and sequencing targeting the 16S rRNA gene, complemented by whole shotgun metagenomics (WGS) to explore the microbial composition and CH4-cycling microorganisms.

Results from Flitwick Moor and the Sebangau Forest showed significantly reduced stem CH4 emissions (<50 µg m-2 hr-1) compared to earlier studies, with trees adopting an upland-like behaviour, displaying heterogenous fluxes with no clear axial pattern or relation to wood properties, as well as CH4 uptake. There was evidence of CH4 oxidation in trees of both ecosystems in the range of 7-47 µg m-3 hr-1. The aerobic and facultative anaerobic bacteria population dominated in tree tissues, and the same number of methanotrophic genera were present in soil and trees, suggesting that microbial groups were recruited from the soil. In A. glutinosa tree tissues a significant positive relation existed between the CH4 oxidising bacteria relative abundance and the oxidation activity. The methanotrophic fraction represented up to 5% of the bacteria in wood, confirming the hypothesis that methanotrophs are ubiquitous in trees of different ecosystems.

CH4-cycling microorganisms are likely to adapt to a soilborne-CH4 gradient up the tree stems; the reduced stem CH4 fluxes in this study resulted from dry soil conditions and potentially from microbial oxidation inside the stem. Conversely, the small proportion of CH4-cycling microorganisms compared to other microbial groups likely reflected the reduced stem CH4 fluxes along the soil-tree continuum. The ratio of CH4-cycling microorganisms might vary across seasons and different hydrological conditions; further long-term studies in forested wetlands will help elucidate the interplay between CH4-cycling microorganisms and stem CH4 fluxes and the importance of trees in balancing CH4 emissions in potentially drier future scenarios.

How to cite: Gomez, C., Pangala, S., Gowing, D., Olsson-Francis, K., Page, S., and Gauci, V.: Wetland trees are a potential methane sink during dry soil conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14034,, 2024.

(Sub)tropical forests
On-site presentation
Daniel Epron, Rawiwan Chotiphan, Ornuma Duangngam, Zixiao Wang, Makoto Shibata, Sumonta Kumar Paul, Poonpipope Kasemsap, and Kannika Sajjaphan

Soils, particularly in upland forests, are the largest biological sink for atmospheric methane (CH4), providing a valuable ecosystem service. Rubber plantations have continually expanded in Southeast Asia, and it is known that converting forests to rubber plantations reduces soil CH4 uptake. However, the effect of management practices, and in particular fertilization, on the methane balance of a rubber plantation has not yet been studied. Rubber plantations cover almost 10% of the country's surface area and almost all rubber plantations are fertilized, two thirds of them intensively or very intensively.

We measured net soil CH4 fluxes over more than a year in a 9-ha experimental rubber plantation with four levels of fertilizer application. We observed a strong and significant reduction of net soil CH4 uptake with increasing fertilisation, which was not explained by differences in CH4 diffusion related to soil water content. Fertilisation not only decreased the methanotrophic activity but also stimulated methanogenic activities probably related to an increase in the availability of nitrogen and labile carbon substrates.

Our results show that intensive fertilization turned soil from methane sink to source, particularly during the rainy season. Given the areas cultivated with rubber trees in Thailand and more widely in South-East Asia, a transition towards rational fertilization of plantations would have a significant positive effect on national reporting greenhouse gas inventories.

How to cite: Epron, D., Chotiphan, R., Duangngam, O., Wang, Z., Shibata, M., Paul, S. K., Kasemsap, P., and Sajjaphan, K.: Fertilization turns a rubber plantation from sink to methane source, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3743,, 2024.

On-site presentation
Holly Blincow, Niall McNaramara, Alison Hoyt, Carla Gomez, Dafydd Elias, Jack Lamb, Rodrigo De Sousa, Darlene Gris, Leonardo Pequeno Reis, and Sunitha Pangala

Trees are recently understood to emit large quantities of CH4 through their stems, particularly in tropical wetland environments. There are still large uncertainties of the processes driving tree CH4 emissions, however, the primary mechanism is thought to be through transfer of CH4 produced in soil into tree biomass and then to the atmosphere. Another possible mechanism is via anaerobic decomposition of rotting tree biomass in stems. In the Brazilian Amazon, very little is known about sources and variability of tree CH4 emissions and how they may vary across different flooded regions.

Across regions of the Amazon we aim to understand the variation of CH4 emissions from trees. These regions are characterised as white water flooded forest (Várzea region) and black water flooded forest (Igapo region). Using two tree species of similar ages across two regions, we measured tree CH4 emissions and surrounding porewater CH4 concentrations for two flooded seasons. Across all study locations and tree species we found large but variable net CH4 emissions ranging from 0.01 to 84 mg m-2 hr-1. These variations in emissions are significantly influenced by the tree species. Furthermore, we measured significantly different fluxes when measuring the same tree species across two regions, suggesting there could be vast alterations in flux when attempting to measure emissions across the Amazon region.

Our work also revealed that CH4 emission was highest at the base of trees (30 cm) compared to measurements made higher up the stem (70 cm). This is consistent with radial diffusion of soil derived CH4 up the stem and also stongly suggests the source of CH4 is soil derived. Porewater concentrations of CH4 throughout the soil column further supports tree CH4 emission deriving from soil.

Furthermore, we analysed the stable isotopic carbon values of emitted CH4 and demonstrate that this vertical reduction in emitted CH4 is also in part a product of biological oxidation of CH4 by methanotrophic bacteria located in woody material. The isotopic profile varied between two tree species and at the base of the tree compared with higher up the stem. We also noted individual tree species had isotopic variability across the two sites.

These results show significant CH4 emissions from trees to atmosphere in the Amazon. By using common tree species of similar ages we demonstrate that the strength and variability of these emissions are strongly influenced by site specific variables that require further investigation.

How to cite: Blincow, H., McNaramara, N., Hoyt, A., Gomez, C., Elias, D., Lamb, J., De Sousa, R., Gris, D., Pequeno Reis, L., and Pangala, S.: Variability of tree methane emissions across regions of the Amazon rainforest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17619,, 2024.

Virtual presentation
Jhon del Aguila Pasquel, Jose Mauro Sousa Moura, Miércio Ferreira Junior, Keven dos Santos Lima, Raphael Tapajos, Laetitia M Brechet, Joost L M van Haren, and Scott R Saleska

Methane (CH4) is a greenhouse gas with 35 times the warming potential of carbon dioxide. In the last 15 years, the concentration of atmospheric CH4 has sharply increased and the signature of carbon stable isotope in CH4 has become more negative suggesting biotic sources, such as tropical wetlands, might be partly responsible of the current atmospheric methane budget. Floodplains in the Brazilian Amazon have been found to release vast amounts of CH4 but the methane dynamics in upland forests are not very well studied. We assessed the magnitude of CH4 fluxes from soil and tree stem surfaces across dry and wet seasons in two contrasting ecosystems in the Central Amazon basin: the seasonally flooded varzea and the upland terra firme forest. Likewise, some potential drivers of such fluxes were assessed: tree diameter, stem height of measurement, tree species, water table depth, and air temperature. Methane fluxes were measured using chamber-based techniques in the period 2022-2023. Overall, greater fluxes were released from the trees stems of the varzea forest during the first half of the wet season (June-August). On the other hand, the stem surface of upland trees emitted very low CH4 fluxes (< 1 mg m-2 h-1). Methane fluxes of most trees from the flooded forests decreased with stem height, a pattern not shown by tree fluxes in the upland forest. The fluxes from tree stem emissions varied by tree species in both forest types: Munguba tree (Pachira aquatica) and Jarana tree emitted more CH4 fluxes than other species in varzea and upland forests, respectively. The next step of our research will be the assessment of the microbial role in the methane cycle of both forest types using a combination of isotopic and -omic techniques.

How to cite: del Aguila Pasquel, J., Sousa Moura, J. M., Junior, M. F., dos Santos Lima, K., Tapajos, R., Brechet, L. M., van Haren, J. L. M., and Saleska, S. R.: Methane fluxes from soil and tree stem surfaces in flooded and non-flooded forests in the Central Amazon basin., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14065,, 2024.

Posters on site: Wed, 17 Apr, 10:45–12:30 | Hall X1

Display time: Wed, 17 Apr 08:30–Wed, 17 Apr 12:30
Chairpersons: Josep Barba, Katerina Machacova
(Hemi)boreal forests
Carl-Fredrik Johannesson, Klaus Steenberg Larsen, Hanna Silvennoinen, Holger Lange, and Jenni Nordén

Soils are key components of the global carbon cycle, releasing CO2 due to plant respiration and microbial decomposition processes and consuming or releasing CH4 depending on the dominance of methanotrophic or methanogenic activity. Gas flux measurements have been, and still are, widely employed to improve our understanding of greenhouse gas budgets as well as the processes and mechanisms regulating them. Thus, accurate estimation of flux rates and dynamics is important.

While there’s a multitude of techniques available for greenhouse gas flux measurements, non-steady state chambers are commonly used. They are however, like other chambers and flux measurement techniques in general, prone to measurement artefacts and biases. When a non-steady state chamber is deployed on top of bare soil, the concentration gradient between the soil and the atmosphere inside the chamber is artificially altered, leading to non-linear gas concentration increases (CO2 and CH4) or decreases (CH4) inside the chamber, even when chamber closure times are short. Whether the true flux rate can still be approximated using linear regression by keeping the chamber closure time short has been discussed for decades and non-linear models rooted in diffusion theory have been developed to account for the non-linearity of the concentration change (e.g., the Hutchinson-Mosier model and the non-steady state diffusive flux estimator (NDFE)). Nonetheless, only few studies have empirically evaluated the effect of chamber closure time on soil flux estimation by linear and non-linear model application, especially using high frequency data.

Using >3 000 forest soil CO2 and CH4 flux measurements collected with a high frequency and precision trace gas concentration analyzer (LI-7810 from LI-COR®), we evaluated the effect of sequentially increasing the time period used for linear and non-linear (Hutchinson-Mosier, (1981)) model fitting, up to a total of 300 seconds. Initial results show that using less time for non-linear model fitting results in higher release estimates for CO2 and higher consumption estimates for CH4 compared to when using the full 300 seconds. We also found that flux estimates from linear and non-linear models converged when decreasing the time period used for the linear fit and increasing the time period used for nonlinear fit, indicating that linear models can provide accurate flux estimates when the time period used for the linear fit is kept short. Our results have implications not only for robust estimation of flux rates, but also for field work and flux measurement logistics and planning.

How to cite: Johannesson, C.-F., Larsen, K. S., Silvennoinen, H., Lange, H., and Nordén, J.: Effect of chamber closure time on soil CH4 and CO2 flux estimation by linear and non-linear model application, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16677,, 2024.

Karelle Rheault, Jesper Riis Christiansen, and Klaus Steenberg Larsen

Greenhouse gas (GHG) emissions, in the form of CO2, CH4 and N2O, from land use change and agriculture are responsible for up to 20% of anthropogenic emissions, mainly due to deforestation, livestock production and crop fertilization. Afforestation is proposed as an effective means to sequester atmospheric carbon in biomass and soils. However, there is a lack of knowledge about the resultant soil GHG fluxes from temperate afforested ecosystems, how they develop in the field and over many years. Furthermore, tree species choice (deciduous/conifers) may impact the soil biogeochemistry differently through the soil physicochemical properties and the soil microbiome with a currently uncertain outcome in relation to GHG fluxes and the climate mitigation potential.

In this study, we investigate the development of soil GHG fluxes, soil physicochemistry, and the soil microbiome on arable land using a well-established forest chronosequence (Vestskoven, Denmark), which is a former cropland area afforested over the last 50 years with Norway spruce (Picea abies), oak (Quercus robur) and beech (Fagus sylvatica). The total of 19 selected sites in Vestskoven includes 6 to 7 stand ages per tree species. We measured CH4 and CO2 fluxes in situ, and sampled soil for physicochemical and microbial analyses.

We present data on how net soil CH4 uptake and soil CO2 efflux develop with time since planting and how the net soil CH4 uptake correlates with the relative abundance of methanotrophic and methanogenic soil communities. We expect these relationships to be dependent of tree species due to differences in how soil physicochemical properties impact the microbial communities responsible for soil CH4 cycling.

Preliminary results show that afforestation increases net soil CH4 uptake, since all tree species had higher net soil CH4 uptake rates compared to cropland, but the effect of plantation age was only visible in oak stands after 50 years. This indicates tree species-specific regulation of the net CH4 flux and its development over time. There was no clear trend for a development of the soil CO2 efflux after planting for either tree species. We will further present analyses of structural equation modelling elucidating the interactions between gas fluxes, soil physicochemical environment and microbial communities. 

How to cite: Rheault, K., Riis Christiansen, J., and Steenberg Larsen, K.: The role of tree species and microbes for the development of net greenhouse gas fluxes from soils after afforestation of agricultural lands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9718,, 2024.

Thomas Schindler, Olga Brovkina, Katerina Machacova, Ülo Mander, and Kaido Soosaar

The research potential to investigate and monitor a peatland site is often limited by difficult accessibility to the site, and a heterogeneous surface with diverse topography, hydrological features, and vegetation. Satellite remote sensing (RS) methods offer the advantage of past-to-present repeating cover research areas compared to field studies. Our case study examined the potential usability of applied satellite RS methods to determine greenhouse gas (GHG) fluxes in natural peatlands. Specifically, we tested several landscape indices on their correlation to GHG fluxes and basic environmental parameters.
The field campaign was carried out from 13.7.2018 to 24.7.2019 in a natural raised bog covered with young pine trees in central Estonia, measuring carbon dioxide (CO2) and methane (CH4) fluxes with manual static chambers, soil temperature, soil moisture, and the water table. The measured air temperature was provided by the nearest meteorological station.  

Land surface temperature (LST) was calculated from satellite Landsat-8 data using open-source code in Google Earth Engine cloud-based service. Normalized Difference Vegetation Index (NDVI), Water Index (NDWI), and Snow Index (NDSI) were calculated from Sentinel-2 data. The relationships between LST and indices with field-measured parameters were explored. Peatland site land covers were mapped using Sentinel-2 data supervised classification into dense trees, sphagnum mosses and grasses, and open water classes. The dynamics of open water locations were estimated based on the distribution of land covers for each month of study period. 

Our correlation analysis reflected different in-situ GHG dynamics throughout the investigated period and the micro-spatial heterogeneity of the land surface, with naturally wetter and dryer spots. The preliminary results show a close relationship between the in-situ measured CO2 fluxes and LST. The CO2 fluxes were further correlated with CH4 fluxes. Distribution of land covers from RS can significantly improve the GHG flux upscaling process. Thus, the obtained results can further help to identify locations in peatlands with the highest risks and priorities to provide detailed in situ monitoring.


This work was supported by the Ministry of Education, Youth and Sports of CR within the CzeCOS program (grant number LM2023048) and project AdAgriF - Advanced methods of greenhouse gases emission reduction and sequestration in agriculture and forest landscape for climate change mitigation (CZ.02.01.01/00/22_008/0004635).

How to cite: Schindler, T., Brovkina, O., Machacova, K., Mander, Ü., and Soosaar, K.: How remote sensing contributes to flux upscaling in natural bog ecosystems – a case study in Estonia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14220,, 2024.

Temperate forests (with overlap to tropical forests)
Luana Krebs, Mana Gharun, Susanne Burri, Iris Feigenwinter, Philip Meier, Liliana Scapucci, and Nina Buchmann

Methane (CH4) and nitrous oxide (N2O) substantially contribute to global greenhouse gas (GHG) emissions together with carbon dioxide (CO2). To understand their impact on future climate change, prioritizing the study of CH4 and N2O fluxes becomes critical. Forest ecosystems, primarily investigated for CO2 exchange, are less explored concerning their exchange of CH4 and N2O. Forests are known to be sinks for CH4, while their role in N2O fluxes varies, acting as either sources or sinks. However, comprehensive studies that concurrently examine CH4 and N2O fluxes in forests, particularly over extended periods and at high elevation, remain scarce. At high altitudes, measuring GHG fluxes with chambers during snowy periods is challenging, leading to a lack of winter flux data which are crucial for understanding flux dynamics related to freeze-thaw cycles and snow patterns. This study addresses this gap by investigating long-term CH4 and N2O fluxes in a subalpine Norway spruce forest (Davos, CH-Dav, ICOS Class 1 Ecosystem station, Switzerland), encompassing both soil and canopy interactions with the atmosphere.

Over five years (2017, 2020-2023 for CH4; 2017, 2020 for N2O), we employed automatic chambers to measure forest-floor fluxes, complemented by below-canopy eddy covariance CH4 flux measurements starting from May 2023, as well as static chamber measurements in 2023. Our research objectives were to 1) characterize the magnitude and seasonal dynamics of CH4 and N2O forest-floor fluxes, and 2) compare CH4 fluxes using chamber and eddy covariance techniques to better understand the interaction of soil and vegetation with the atmosphere.

We hypothesized that the forest floor primarily acts as a net sink for CH4, with soil temperature and snow dynamics being important drivers due to their impact on microbial activity and diffusion rates between soil and atmosphere. Given the low nitrogen availability at the study site, we anticipated very low N2O emissions. Additionally, we hypothesized that comparing CH4 fluxes from chambers and eddy covariance would reveal small differences in their magnitudes, attributable to the distinct measurement scales and scopes of these two techniques. Our results confirmed the forest floor as a consistent CH4 sink, exhibiting substantial short-term fluctuations driven predominantly by air temperature and snow cover. N2O fluxes were negligible over the two-year observation period. Our study contributes to a deeper understanding of how environmental drivers and seasonal dynamics influence CH4 and N2O fluxes in high-elevation forests.

How to cite: Krebs, L., Gharun, M., Burri, S., Feigenwinter, I., Meier, P., Scapucci, L., and Buchmann, N.: Long-term observations of CH4 and N2O fluxes in a subalpine Norway spruce forest using chamber and eddy covariance methods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11317,, 2024.

Katerina Machacova, Thomas Schindler, Hannes Warlo, and Rossella Guerrieri

European beech (Fagus sylvatica L.) is a native and widely grown tree species typical for upland forests of Central and Southeast Europe. The soils of beech forests are regarded as predominant sources of nitrous oxide (N2O), sinks of methane (CH4) and sources of carbon dioxide (CO2), while the contribution of beech trees themselves to the ecosystem greenhouse gas (GHG) exchange varies by gas species and site. Moreover, forest nitrogen (N) and carbon cycling, and thus N2O, CH4 and CO2 turnover processes are affected by N deposition, yet, the long-term effect of N deposition on GHG exchange of soil and mature trees is far from being understood.

We aimed to investigate whether an increase in N deposition can alter forest GHG emissions. In September 2023, we measured N2O, CH4 and CO2 exchange of beech stems and adjacent soil, and various environmental parameters in a mature pre-alpine beech forest in Northeastern Italy, where a N manipulation experiment (4 treatments each replicated in 3 plots) has been carried out since 2015. Four experimental plots were selected: control (N0, only ambient deposition), canopy N addition (N30A, +30 kg ha-1 yr-1 sprayed over tree canopies) and soil N additions with two different doses (N30 and N60, +30 and +60 kg ha-1 yr-1, respectively).

The stems of mature beech trees were net sinks of CH4 (-11.9 ± 3.6 mg ha-1 ground area h-1, median ± 95% confidence interval) and sources of CO2 (639 ± 137 g ha-1 h-1), their N2O exchange potential (3.36 ± 3.82 mg ha-1 h-1) was rather low. The stem fluxes of all three GHGs were not affected by nine years of N treatment.

The long-term N deposition did not alter the soil CO2 emission (3015 ± 193 g ha-1 h-1). However, the N addition to the soil tended to increase the soil CH4 uptake (-642 ± 61 versus -901 ± 69 mg ha-1 h-1, N0+N30A versus N30+N60 plots). The soil N2O emissions were highest at the control plot (82.4 ± 33.9 mg ha-1 h-1), whereas the plots N30A and N60 showed significantly lower fluxes (1.56 ± 12.41 mg ha-1 h-1).

Our preliminary results detected high spatial variability in stem and soil GHG fluxes, which might be rather connected to the variable site topography than to the long-term N deposition effect. Future detailed soil GHG flux measurements across all experimental plots replicates will help to understand this variability and the effect of N deposition on the GHG fluxes.



This research was supported by the Ministry of Education, Youth and Sports of CR within the programs CzeCOS (grant number LM2023048) and LU - INTER-EXCELLENCE II (grant number LUC23162). We thank Federico Magnani and Alessandra Teglia from the University of Bologna and Reparto Carabinieri Biodiversità in Pian del Cansiglio for scientific and logistic support, respectively.

How to cite: Machacova, K., Schindler, T., Warlo, H., and Guerrieri, R.: Long-term nitrogen deposition does not affect nitrous oxide, methane and carbon dioxide exchange of mature beech tree stems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3135,, 2024.

Josep Barba and Vincent Gauci

Trees can emit methane to the atmosphere through the stems. These fluxes might represent a large (and still unaccounted for) source of methane from forests to the atmosphere, but the uncertainties related with the spatial variability are still too large for properly estimating their contribution to the regional CH4 budgets. The general understanding is that these emissions are microbial–produced (either originated in soils or in the heartwood of trees), and thus, they are assumed to be temperature-and-water dependent. However, this assumption has not been tested yet at large scales, from different and contrasted ecosystems and with multiple species. In this study, we measured stem CH4 fluxes on more than 400 trees from 28 different species, spanning temperate, Mediterranean and tropical ecosystems. Our main goal was to distinguish between site-specific, species-specific, and environmental effects on controlling stem CH4 fluxes. Preliminary results showed that species identity regulates stem CH4 fluxes independently of environmental conditions, which might be due to wood properties providing a range of internal stem microhabitats for methanogenic communities or controlling gas diffusivity through the wood.  

How to cite: Barba, J. and Gauci, V.: Environmentally-uncoupled tree stem methane fluxes from temperate, Mediterranean and tropical upland ecosystems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20545,, 2024.

Tropical forests
Hellen F. V. Cunha, Sam P. Jones, Hella Van Asperen, Santiago Botía, Shujiro Komiya, Lívia Rosalem, Jochen Schöngart, Maria Teresa Fernandez Piedade, Daniel Magnabosco Marra, Florian Wittmann, and Susan Trumbore

Trees can significantly influence the net exchange of methane between forests and the atmosphere but what controls this behaviour in hyper-diverse ecosystems of the Central Amazon is not well defined. Variations in topography and rainfall cause predictable, but poorly documented, changes to the balance between methanotrophy and metanogenesis in soils and sediments across the landscape and between seasons. Trees can act as conduits for methane produced below-ground, however, the rate of such transport is mediated by inter and intra-species traits that need to be understood.

To better understand the relationships among methane exchange, topographic position, seasonal rainfall and tree species in forests of the Central Amazon, we are conducting two related studies within the Uatumã Sustainable Development Reserve and Amazon Tall Tower Observatory, Amazonas, Brazil. The first is measuring soil and stem fluxes in six plots (6 trees / plot) along a topographic transition from a well-drained plateau, through slopes to a waterlogged valley. The second study is focusing on stem fluxes from six different species (5 trees / species), with differences in wood density and phenology, growing at a similar elevation in an Igapó forest of the adjacent Uatumã river. These observations, starting in September 2023, are being made every 2-3 months to capture the influence of seasonal rainfall and inundation.

During the dry season (September, 2023), soils in the plateau (-1.4 ± 0.27 nmol m-2 s-1) and slope (-1.66 ± 0.11 to -1.20 ± 0.29 nmol m-2 s-1) plots acted as a sink for methane, whilst, those in the valley plot where a source (11.40 ± 2.56 nmol m-2 s-1 ). Reflecting this pattern, stem emissions were mostly observed in the valley (10.7 ± 4.71 nmol m-2 s-1) and in particular from the palm Mauritia flexuosa. Stem fluxes in the plateau and slope plots were marginal (0.0028 ± 0.0039 to 0.224 ± 0.0554 nmol m-2 s-1). In the Igapó (November, 2023), the exposed soil behaved as a sink for methane. Differences were observed among the species studied, with the largest emissions from Nectandra amazonum – low wood density group (0.64 ± 0.14 nmol m-2 s-1 ) and Inga sp. – high wood density group (0.39 ± 0.049 nmol m-2 s-1), while the other 4 species had lower emissions (0.0023 ± 0.01 to 0.10 ± 0.01 nmol m-2 s-1). Together these results support methane produced below-ground as the main source of tree emissions across this landscape and highlight the need to take species composition into account when considering the net exchange of methane from these ecosystems.

How to cite: F. V. Cunha, H., P. Jones, S., Van Asperen, H., Botía, S., Komiya, S., Rosalem, L., Schöngart, J., Fernandez Piedade, M. T., Magnabosco Marra, D., Wittmann, F., and Trumbore, S.: Stem and soil methane fluxes of different ecosystems in Central Amazon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5902,, 2024.

Khandaker Mohammed Rezaul Karim, Md Abdul Halim, and Sean Thomas

Comprising 45% of global forest cover, tropical forests are pivotal in the GHG budgets. Emerging research highlights the significance of tropical trees as CH4 sources, yet tree-foliage emissions have been minimally investigated. Moreover, the N2O fluxes from tropical tree foliage remain almost completely unexamined.

Objectives: This study presents a comprehensive survey of foliar CH4 and N2O fluxes across tropical forest tree species using integrated output spectroscopy and a purpose-built cuvette system for accurate in-situ flux rate measurements. It tests two key hypotheses: (1) broadleaf trees in well-drained soils of tropical forests exhibit foliar CH4 oxidation; (2) foliar CH4 and N2O flux patterns vary systematically among ecological and phylogenetic groups.

Methods: We measured foliar fluxes from 120 trees across 40 species within Lawachara National Park, Bangladesh, an upland mixed-tropical-evergreen forest, prioritizing diverse shade-tolerant canopy trees. We utilized a dynamic leaf chamber (CS-LC7000) with continuous gas flow and portable CH4 (LGR 915-001) and N2O (LI-7820) analyzers, alongside concurrent measurements of CO2 and H2O flux. In addition to gas flux data, our study incorporated leaf trait measurements (of leaf mass per area and leaf N content).

Results: Across all samples, the mean CH4 flux of 0.016 nmol m-2 s-1 did not display a significant deviation from zero (t = 19.44, df = 827, p > 0.05). In contrast, the mean N2O flux 0.54 nmol m-2 s-1, exhibited a significant elevation above zero (t = 19.42, df = 827, p < 0.001), indicating notable N2O emissions on average. Methane flux varied among species and various ecological successional groups, namely pioneer, mid-successional, and late successional species (F = 5.99, df = 2, p < 0.01). Pioneer species, which were sources of CH­4, demonstrated significantly higher CH4 flux compared to both mid (p < 0.01) and late successional (p < 0.05) species, which both acted as weak CH4 sinks. All ecological groups were sources of N2O, with significant variations among the ecological successional groups (F = 12.97, df = 2, p < 0.01). Pioneer species were identified as the highest emitters of N2O, followed by mid and late-successional species.

A comparative CH4 flux analysis among the 28 families revealed significant variability (F = 47.7, df = 27, p < 0.01), with certain species acting as sources and others as sinks of CH4. Notably, 11 families were classified as CH4 sources, while the remainder functioned as sinks. Meliaceae emerged as having the highest average CH4 emissions, and Thymeliaceae the greatest CH4 consumption. Similarly, a distinct variation in N2O flux was observed among families (F = 6.57, df = 27, p < 0.01), with Sapindaceae showing the highest, and Rubiaceae and Euphorbiaceae the lowest N2O emissions.

Conclusions: This study on foliar CH4 and N2O fluxes in tropical forests reveals trees' crucial role in greenhouse gas emissions. Pioneer species emerge as major emitters of both CH4 and N2O, suggesting that foliar emissions of these GHGs may be pronounced in secondary forests, and hence the importance of conserving intact forests dominated by later-successional species.

How to cite: Karim, K. M. R., Halim, M. A., and Thomas, S.: Foliar Methane and Nitrous Oxide Fluxes: A Comprehensive Study in Tropical Forest Ecosystems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11673,, 2024.

Laëtitia Brechet, Mercedes Ibáñez, Benoît Burban, Jean-Yves Goret, Clément Stahl, Damien Bonal, Rob Jackson, and Ivan Janssens

Tropical forests play a key role in the global carbon balance and in natural climate change mitigation, as they account for 68% of global forest carbon stocks and represent up to 30% of global soil carbon stocks. However, major uncertainties remain regarding the long-term sustainability of their carbon sink capacity when considering the full greenhouse gas exchange, including methane (CH4) and nitrous oxide (N2O) fluxes, and accurately identifying and quantifying all sources and sinks.

In this line, we present here original continuous high-frequency ecosystem (eddy covariance) and soil (automated chamber) CH4 and N2O flux data from a 2.5-year study in a seasonally wet tropical forest at the Guyaflux experimental site, French Guiana. The main objective of our study was to assess the seasonal patterns of CH4 and N2O exchange at the ecosystem and soil levels, and to identify the environmental drivers. Seasonal variations in ecosystem and soil CH4 and N2O fluxes were tremendous, with generally higher CH4 and N2O emissions in the wettest than in the driest season. Global radiation, soil water content and soil temperature were the main drivers of seasonal variation in ecosystem and soil CH4 and N2O fluxes. Furthermore, based on eddy covariance measurements of all greenhouse gases, i.e. CH4, N2O and CO2, the forest was overall a significant carbon sink (-1,875 ± 813 kgC ha-1 y-1, i.e. cumulative net ecosystem exchange), although the ecosystem shifted from a small sink to a small source of CH4 during the wettest season, and remained a more or less small but constant source of N2O. In contrast, soil fluxes in the upper part of the forest within the tower footprint were consistently a CH4 sink, while soil N2O fluxes shifted depending on the season, from a small N2O sink in the driest season to a small source in the wettest season.

Our study shows that the carbon sink potential of the Guyaflux forest is not yet compromised by CH4 and N2O emissions. However, under the more frequent extreme conditions of contrasting soil water content and global radiation expected in the future, CH4 and N2O emissions may increase and thus reduce the forest carbon sink.

How to cite: Brechet, L., Ibáñez, M., Burban, B., Goret, J.-Y., Stahl, C., Bonal, D., Jackson, R., and Janssens, I.: Seasonal variation in ecosystem and soil methane and nitrous oxide fluxes in a tropical rainforest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9235,, 2024.