Trees are major conduits for methane egress from tropical forested wetlands

Pangala, Sunitha Rao; Moore, Sam; Hornibrook, Edward R. C.; Gauci, Vincent

doi:10.1111/nph.12031

Cited by 177 publications

(260 citation statements)

References 48 publications

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“…Evaluating how land use change alters the radiative forcing of tropical peat swamps emissions requires consideration of plant mediated release of greenhouse gases, which may constitute a substantial component of emissions both for rice (Neue et al 1997) and trees in tropical wetlands (e.g. 21 % of CH 4 fluxes in tropical peat swamps in SE Asia) (Pangala et al 2013). Furthermore, to fully determine how land use change impact the radiative forcing, both the C losses due to fire in the initial phase of land clearance and the photosynthestic activity of the vegetation need to be considered (Malhi et al 2011;Sjögersten et al 2014;Turetsky et al 2014a).…”

Section: Discussionmentioning

confidence: 99%

Root oxygen loss from Raphia taedigera palms mediates greenhouse gas emissions in lowland neotropical peatlands

et al. 2016

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Aims Little is known about the influence of vegetation on the timing and quantities of greenhouse gas fluxes from lowland Neotropical peatlands to the atmosphere. To address this knowledge gap, we investigated if palm forests moderate greenhouse gas fluxes from tropical peatlands due to radial oxygen loss from roots into the peat matrix. Methods We compared the diurnal pattern of greenhouse gas fluxes from peat monoliths with and without seedlings of Raphia taedigera palm, and monitored the effect of land use change on greenhouse gas fluxes from R. taedigera palm swamps in Bocas del Toro, Panama. Results CH 4 fluxes from peat monoliths with R. taedigera seedlings varied diurnally, with the greatest emissions during daytime. Radial oxygen loss from the roots of R. taedigera seedlings partially supressed CH 4 emissions at midday; this suppression increased as seedlings grew. On a larger scale, removal of R. taedigera palms for agriculture increased CH 4 and N 2 O fluxes, but decreased CO 2 fluxes when compared to nearby intact palm forest. The net impact of forest clearance was a doubling of the radiative forcing. Conclusions R. taedigera palm forest influences the emission of greenhouse gases from lowland tropical peatlands through radial oxygen loss into the rhizosphere.

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Section: Discussionmentioning

confidence: 99%

Root oxygen loss from Raphia taedigera palms mediates greenhouse gas emissions in lowland neotropical peatlands

et al. 2016

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“…Granville (1969) described the presence of such tissues in the aerating pneumatophores of M. flexuosa palms. These pneumatophores may also conduct N 2 O or CH 4 produced in the anoxic soil layers to the atmosphere, as has been shown for aerenchymous tissues in the stalks of rice (see, e.g., Minoda and Kimura 1994) as well as for tree stem lenticels in temperate and tropical forested wetlands (Gauci et al 2010;Pangala et al 2013). In this way, CH 4 is directly emitted from the soil, and avoids potential oxidation in upper aerobic soil layers.…”

Section: Introductionmentioning

confidence: 98%

Greenhouse gas emissions along a peat swamp forest degradation gradient in the Peruvian Amazon: soil moisture and palm roots effects

Lent

Hergoualc’h

Verchot

et al. 2018

Mitig Adapt Strateg Glob Change

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Tropical peatlands in the Peruvian Amazon exhibit high densities of Mauritia flexuosa palms, which are often cut instead of being climbed for collecting their fruits. This is an important type of forest degradation in the region that could lead to changes in the structure and composition of the forest, quality and quantity of inputs to the peat, soil properties, and greenhouse gas (GHG) fluxes. We studied peat and litterfall characteristics along a forest degradation gradient that included an intact site, a moderately degraded site, and a heavily degraded site. To understand underlying factors driving GHG emissions, we examined the response of in vitro soil microbial GHG emissions to soil moisture variation, and we tested the potential of pneumatophores to conduct GHGs in situ. The soil phosphorus and carbon content and carbon-to-nitrogen ratio as well as the litterfall nitrogen content and carbon-to-nitrogen ratio were significantly affected by forest degradation. Soils from the degraded sites consistently produced more carbon dioxide (CO 2 ) than soils from the intact site during in vitro incubations. The response of CO 2 production to changes in water-filled pore space (WFPS) followed a cubic polynomial relationship with maxima at 60-70% at the three sites. Methane (CH 4 ) was produced in limited amounts and exclusively under watersaturated conditions. There was no significant response of nitrous oxide (N 2 O) emissions to WFPS variation. Lastly, the density of pneumatophore decreased drastically as the result of forest degradation and was positively correlated to in situ CH 4 emissions. We conclude that CIAT, Cali, Colombia recurrent M. flexuosa harvesting could result in a significant increase of in situ CO 2 fluxes and a simultaneous decrease in CH 4 emissions via pneumatophores. These changes might alter long-term carbon and GHG balances of the peat, and the role of these ecosystems for climate change mitigation, which stresses the need for their protection.

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“…Third, the stems of living trees commonly provide an environment suitable for microbial methanogenesis (Covey et al, 2012). Static chambers demonstrate locally significant through-bark flux from both soil-based (Pangala et al, 2013(Pangala et al, , 2015, and tree-stem-based methanogens . These studies indicate trees are a significant factor regulating ecosystem flux; however, estimates of biogenic plant-mediated methane emissions at broad scales are complicated by overlap with methane consumption in upland soil and production in wetlands.…”

Section: Vegetationmentioning

confidence: 99%

The global methane budget 2000–2012

Saunois

Bousquet

Poulter

et al. 2016

Earth Syst. Sci. Data

933

733

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Abstract. The global methane (CH 4 ) budget is becoming an increasingly important component for managing realistic pathways to mitigate climate change. This relevance, due to a shorter atmospheric lifetime and a stronger warming potential than carbon dioxide, is challenged by the still unexplained changes of atmospheric CH 4 over the past decade. Emissions and concentrations of CH 4 are continuing to increase, making CH 4 the second most important human-induced greenhouse gas after carbon dioxide. Two major difficulties in reducing uncertainties come from the large variety of diffusive CH 4 sources that overlap geographically, and from the destruction of CH 4 by the very short-lived hydroxyl radical (OH). To address these difficulties, we have established a consortium of multi-disciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate research on the methane cycle, and producing regular (∼ biennial) updates of the global methane budget. This consortium includes atmospheric physicists and chemists, biogeochemists of surface and marine emissions, and socio-economists who study anthropogenic emissions. Following Kirschke et al. (2013), we propose here the first version of a living review paper that integrates results of top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up models, inventories and data-driven approaches (including process-based models for estimating land surface emissions and atmospheric chemistry, and inventories for anthropogenic emissions, data-driven extrapolations). . Top-down inversions consistently infer lower emissions in China (∼ 58 Tg CH 4 yr −1 , range 51-72, −14 %) and higher emissions in Africa (86 Tg CH 4 yr −1 , range 73-108, +19 %) than bottom-up values used as prior estimates. Overall, uncertainties for anthropogenic emissions appear smaller than those from natural sources, and the uncertainties on source categories appear larger for top-down inversions than for bottom-up inventories and models.The most important source of uncertainty on the methane budget is attributable to emissions from wetland and other inland waters. We show that the wetland extent could contribute 30-40 % on the estimated range for wetland emissions. Other priorities for improving the methane budget include the following: (i) the development of process-based models for inland-water emissions, (ii) the intensification of methane observations at local scale (flux measurements) to constrain bottom-up land surface models, and at regional scale (surface networks and satellites) to constrain top-down inversions, (iii) improvements in the estimation of atmospheric loss by OH, and (iv) improvements of the transport models integrated in top-down inversions.

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Trees are major conduits for methane egress from tropical forested wetlands

Cited by 177 publications

References 48 publications

Root oxygen loss from Raphia taedigera palms mediates greenhouse gas emissions in lowland neotropical peatlands

Root oxygen loss from Raphia taedigera palms mediates greenhouse gas emissions in lowland neotropical peatlands

Greenhouse gas emissions along a peat swamp forest degradation gradient in the Peruvian Amazon: soil moisture and palm roots effects

The global methane budget 2000–2012

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