Seasonal dynamics of stem N2O exchange follow the physiological activity of boreal trees

Macháčová, Kateřina; Vainio, Elisa; Urban, Otmar; Pihlatie, Mari

doi:10.1038/s41467-019-12976-y

Cited by 45 publications

(55 citation statements)

References 60 publications

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“…Likewise, full-year investigations of gas emissions might change the results. For instance, Machacova et al 47 found a clear N 2 O emission peak from stems of boreal trees during the vegetation season/summer while there was no effect of soil water content on tree N 2 O fluxes in the vegetation season.…”

Section: Main Controllers Of Ch 4 and N 2 O Fluxes Methane Is Producmentioning

confidence: 99%

Short-term flooding increases CH4 and N2O emissions from trees in a riparian forest soil-stem continuum

Schindler

Mander

Macháčová

et al. 2020

Sci Rep

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One of the characteristics of global climate change is the increase in extreme climate events, e.g., droughts and floods. Forest adaptation strategies to extreme climate events are the key to predict ecosystem responses to global change. Severe floods alter the hydrological regime of an ecosystem which influences biochemical processes that control greenhouse gas fluxes. We conducted a flooding experiment in a mature grey alder (Alnus incana (L.) Moench) forest to understand flux dynamics in the soil-tree-atmosphere continuum related to ecosystem N 2 O and CH 4 turn-over. The gas exchange was determined at adjacent soil-tree-pairs: stem fluxes were measured in vertical profiles using manual static chambers and gas chromatography; soil fluxes were measured with automated chambers connected to a gas analyser. The tree stems and soil surface were net sources of N 2 O and CH 4 during the flooding. Contrary to N 2 O, the increase in CH 4 fluxes delayed in response to flooding. Stem N 2 O fluxes were lower although stem CH 4 emissions were significantly higher than from soil after the flooding. Stem fluxes decreased with stem height. Our flooding experiment indicated soil water and nitrogen content as the main controlling factors of stem and soil N 2 O fluxes. The stems contributed up to 88% of CH 4 emissions to the stem-soil continuum during the investigated period but soil N 2 O fluxes dominated (up to 16 times the stem fluxes) during all periods. Conclusively, stem fluxes of CH 4 and N 2 O are essential elements in forest carbon and nitrogen cycles and must be included in relevant models.Greenhouse gases (GHG), in particular, methane (CH 4 ) and nitrous oxide (N 2 O) contribute 16% and 6% to global warming, respectively 1 . In addition, N 2 O is a dangerous stratospheric O 3 layer depleting agent 2 . Due to the increasing emissions, both gases have high radiative forcing potential. In principle, terrestrial biosphere may be seen as a net source of GHG to the atmosphere 3 . Temperate as well as tropical forest soils (in general) seem to be a central natural emitting source of N 2 O, on the one hand, a natural sink of CH 4 on the other 4-9 . Flux estimations of N 2 O and CH 4 in forest systems are mainly based on studies of forest soil measurements, usually excluding exchange potential of vegetation 5,7,10 . Nevertheless, investigations on GHG fluxes from plants in wetland or riparian ecosystems show that plants, especially trees, can be essential sources of CH 4 and N 2 O 9,11-13 . However, recent studies uncover the relevance of tree stem surfaces playing an important role in understanding GHG dynamics in different forest ecosystems 8,9,14 .Grey alder (Alnus incana (L.) Moench)) is a fast-growing, pioneer tree species with excellent potential for short-rotation forestry in the Northern hemisphere [15][16][17][18] . Due to the symbiotic Frankia bacteria which fix atmospheric nitrogen, alder forests are important nitrogen sequestering ecosystems 19,20 . Decomposition of nutrient-rich alder litter improves soil properti...

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Section: Main Controllers Of Ch 4 and N 2 O Fluxes Methane Is Producmentioning

confidence: 99%

Short-term flooding increases CH4 and N2O emissions from trees in a riparian forest soil-stem continuum

Schindler

Mander

Macháčová

et al. 2020

Sci Rep

Self Cite

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“…These methods include both soil and rice plants in the same system [10,18,[59][60][61], making it difficult to evaluate the role of rice plants. However, for other plants with bigger stems (like trees), recent studies have developed separate chambers that help to capture the fluxes of N 2 O by avoiding soil N 2 O emissions [62]. The chamber used for trees cannot be used for crop species, like rice.…”

Section: Why It Is a Challenge To Understand The Role Of Rice Plants mentioning

confidence: 99%

Nitrous Oxide Emissions from Paddies: Understanding the Role of Rice Plants

Timilsina

Bizimana

Pandey

et al. 2020

Plants

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Paddies are a potential source of anthropogenic nitrous oxide (N2O) emission. In paddies, both the soil and the rice plants emit N2O into the atmosphere. The rice plant in the paddy is considered to act as a channel between the soil and the atmosphere for N2O emission. However, recent studies suggest that plants can also produce N2O, while the mechanism of N2O formation in plants is unknown. Consequently, the rice plant is only regarded as a channel for N2O produced by soil microorganisms. The emission of N2O by aseptically grown plants and the distinct dual isotopocule fingerprint of plant-emitted N2O, as reported by various studies, support the production of N2O in plants. Herein, we propose a potential pathway of N2O formation in the rice plant. In rice plants, N2O might be formed in the mitochondria via the nitrate–nitrite–nitric oxide (NO3–NO2–NO) pathway when the cells experience hypoxic or anoxic stress. The pathway is catalyzed by various enzymes, which have been described. So, N2O emitted from paddies might have two origins, namely soil microorganisms and rice plants. So, regarding rice plants only as a medium to transport the microorganism-produced N2O might be misleading in understanding the role of rice plants in the paddy. As rice cultivation is a major agricultural activity worldwide, not understanding the pathway of N2O formation in rice plants would create more uncertainties in the N2O budget.

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“…Thus, it is likely that a combination of sufficient water availability, sap flow intensity and rising temperatures led to peak stem CH4 emission in our study. Aside from sap flow intensity, stem CO2 emissions could be used as an indicator for respiration and hence indirectly for physiological activity of the tree (Hölttä & Kolari, 2009;Machacova et al, 2019), that may explain stem CH4 emissions (Barba et al, 2017). However, in our study stem CO2 emissions at AW could only explain 1% of all CH4 fluxes larger than 0.1 mg m -2 h -1 (tested with linear models, data not shown).…”

Section: Drained Vs Undrained Alder Forestmentioning

confidence: 56%

Mature black alder shows intermittent events of high stem methane emissions

Köhn

Günther

Schwabe

et al. 2020

Preprint

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SummaryTree stems can be a source of the greenhouse gas methane (CH4). However, assessments of the global importance are complicated by a lack of research and a high variability between ecosystems. Here, we determined the contribution of emissions from tree stems of mature black alder (Alnus glutinosa (L.) Gaertn.) to overall CH4 exchange in two temperate peatlands.We measured emissions from stems and soils using closed chambers in a drained and a wet alder forest over two years. Further, we studied the importance of alder leaves as substrate for methanogenesis in an incubation experiment.Stem CH4 emissions were shortlived and occurred only during times of inundation at the wet site. The drained site did not show stem emissions and the soil acted as a small CH4 sink. The contribution of stem emissions to the overall CH4 budget was below 0.3% in both sites.Our results show that also mature black alders intermittently can be a source of CH4. However, the low share of stem-mediated CH4 emissions in both forests may indicate that this pathway is only of minor relative importance in temperate peatlands.

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Seasonal dynamics of stem N2O exchange follow the physiological activity of boreal trees

Cited by 45 publications

References 60 publications

Short-term flooding increases CH4 and N2O emissions from trees in a riparian forest soil-stem continuum

Short-term flooding increases CH4 and N2O emissions from trees in a riparian forest soil-stem continuum

Nitrous Oxide Emissions from Paddies: Understanding the Role of Rice Plants

Mature black alder shows intermittent events of high stem methane emissions

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