Limits...
Environmental and vegetation controls on the spatial variability of CH4 emission from wet-sedge and tussock tundra ecosystems in the Arctic.

McEwing KR, Fisher JP, Zona D - Plant Soil (2015)

Bottom Line: All sites were found to be sources of CH4, with northern sites (in Barrow) showing similar CH4 emission rates to the southernmost site (ca. 300 km south, Ivotuk).Greater vascular plant cover was linked with higher CH4 emission, but this increased emission with increased vascular plant cover was much higher (86 %) in the drier sites, than the wettest sites (30 %), suggesting that transport and/or substrate availability were crucial limiting factors for CH4 emission in these tundra ecosystems.Overall, this study provides an increased understanding of the fine scale spatial controls on CH4 flux, in particular the key role that plant cover and GPP play in enhancing CH4 emissions from tundra soils.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal and Plant Science, University of Sheffield, Western Bank, Sheffield S10 2TN UK.

ABSTRACT

Aims: Despite multiple studies investigating the environmental controls on CH4 fluxes from arctic tundra ecosystems, the high spatial variability of CH4 emissions is not fully understood. This makes the upscaling of CH4 fluxes from plot to regional scale, particularly challenging. The goal of this study is to refine our knowledge of the spatial variability and controls on CH4 emission from tundra ecosystems.

Methods: CH4 fluxes were measured in four sites across a variety of wet-sedge and tussock tundra ecosystems in Alaska using chambers and a Los Gatos CO2 and CH4 gas analyser.

Results: All sites were found to be sources of CH4, with northern sites (in Barrow) showing similar CH4 emission rates to the southernmost site (ca. 300 km south, Ivotuk). Gross primary productivity (GPP), water level and soil temperature were the most important environmental controls on CH4 emission. Greater vascular plant cover was linked with higher CH4 emission, but this increased emission with increased vascular plant cover was much higher (86 %) in the drier sites, than the wettest sites (30 %), suggesting that transport and/or substrate availability were crucial limiting factors for CH4 emission in these tundra ecosystems.

Conclusions: Overall, this study provides an increased understanding of the fine scale spatial controls on CH4 flux, in particular the key role that plant cover and GPP play in enhancing CH4 emissions from tundra soils.

No MeSH data available.


CH4 exchange within arctic tundra. CH4 is transported to the atmosphere directly through diffusion from the soil and indirectly through the roots and stems of vascular plants. In opposition, CH4 oxidation is aided by O2 diffusion directly into the soil and root aeration
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Fig6: CH4 exchange within arctic tundra. CH4 is transported to the atmosphere directly through diffusion from the soil and indirectly through the roots and stems of vascular plants. In opposition, CH4 oxidation is aided by O2 diffusion directly into the soil and root aeration

Mentions: The most significant control on CH4 fluxes across all the sites was found to be GPP. This may suggest a dominant role of plant productivity on CH4 emissions, as higher plant productivity (i.e., higher GPP) is likely to stimulate CH4 emission by providing photosynthetically derived substrates for methanogenic processes (Harazono et al. 2006; Lai et al. 2014b). However those plots with the highest GPP also tended to have a greater percentage cover of vascular plants, meaning both substrate input and the provision of CH4 transport pathways may have increased simultaneously (Lai et al. 2014b; Shannon et al. 1996; Fig. 6). In comparison to mosses, vascular plants have a higher photosynthetic capacity and their substantial root exudation and litter input increase substrate availability for methane production (Olivas et al. 2011; Riutta et al. 2007). Furthermore, vascular plants play a critical role in the transport of CH4 from the soil (Joabsson et al. 1999; Noyce et al. 2014), which is a key limit on CH4 flux, where emissions can depend more on the transport than CH4 production itself (Born et al. 1990; Harazono et al. 2006). With an absence of vascular plants, within drier sites at the polygon rims, limitation of transport and/or substrate availability appeared to be of major relevance in suppressing CH4 emission to relatively low levels (Fig. 5 and Fig. 6). For this reason, very low CH4 emissions were observed with low vascular plant cover (<10 %) within dry oxic sites (Fig. 5) in comparison to wet sites at the polygon centre, where CH4 can diffuse directly from the surface water (Fig. 6). However, in sites with vascular plants present, CH4 was transported through plant stems, bypassing oxic soil layers where it would otherwise be re-oxidised by methanotrophs (Joabsson and Christensen 2001; Shannon et al. 1996; Fig. 6). Mechanistically, vascular plants act as a conduit for methanogenesis, connecting the CH4 produced at depth within the soil to the atmosphere, thereby enhancing the release of CH4 (von Fischer et al. 2010; Harazono et al. 2006; Joabsson and Christensen 2001; Sebacher et al. 1985; Shannon et al. 1996).Fig 6


Environmental and vegetation controls on the spatial variability of CH4 emission from wet-sedge and tussock tundra ecosystems in the Arctic.

McEwing KR, Fisher JP, Zona D - Plant Soil (2015)

CH4 exchange within arctic tundra. CH4 is transported to the atmosphere directly through diffusion from the soil and indirectly through the roots and stems of vascular plants. In opposition, CH4 oxidation is aided by O2 diffusion directly into the soil and root aeration
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4372828&req=5

Fig6: CH4 exchange within arctic tundra. CH4 is transported to the atmosphere directly through diffusion from the soil and indirectly through the roots and stems of vascular plants. In opposition, CH4 oxidation is aided by O2 diffusion directly into the soil and root aeration
Mentions: The most significant control on CH4 fluxes across all the sites was found to be GPP. This may suggest a dominant role of plant productivity on CH4 emissions, as higher plant productivity (i.e., higher GPP) is likely to stimulate CH4 emission by providing photosynthetically derived substrates for methanogenic processes (Harazono et al. 2006; Lai et al. 2014b). However those plots with the highest GPP also tended to have a greater percentage cover of vascular plants, meaning both substrate input and the provision of CH4 transport pathways may have increased simultaneously (Lai et al. 2014b; Shannon et al. 1996; Fig. 6). In comparison to mosses, vascular plants have a higher photosynthetic capacity and their substantial root exudation and litter input increase substrate availability for methane production (Olivas et al. 2011; Riutta et al. 2007). Furthermore, vascular plants play a critical role in the transport of CH4 from the soil (Joabsson et al. 1999; Noyce et al. 2014), which is a key limit on CH4 flux, where emissions can depend more on the transport than CH4 production itself (Born et al. 1990; Harazono et al. 2006). With an absence of vascular plants, within drier sites at the polygon rims, limitation of transport and/or substrate availability appeared to be of major relevance in suppressing CH4 emission to relatively low levels (Fig. 5 and Fig. 6). For this reason, very low CH4 emissions were observed with low vascular plant cover (<10 %) within dry oxic sites (Fig. 5) in comparison to wet sites at the polygon centre, where CH4 can diffuse directly from the surface water (Fig. 6). However, in sites with vascular plants present, CH4 was transported through plant stems, bypassing oxic soil layers where it would otherwise be re-oxidised by methanotrophs (Joabsson and Christensen 2001; Shannon et al. 1996; Fig. 6). Mechanistically, vascular plants act as a conduit for methanogenesis, connecting the CH4 produced at depth within the soil to the atmosphere, thereby enhancing the release of CH4 (von Fischer et al. 2010; Harazono et al. 2006; Joabsson and Christensen 2001; Sebacher et al. 1985; Shannon et al. 1996).Fig 6

Bottom Line: All sites were found to be sources of CH4, with northern sites (in Barrow) showing similar CH4 emission rates to the southernmost site (ca. 300 km south, Ivotuk).Greater vascular plant cover was linked with higher CH4 emission, but this increased emission with increased vascular plant cover was much higher (86 %) in the drier sites, than the wettest sites (30 %), suggesting that transport and/or substrate availability were crucial limiting factors for CH4 emission in these tundra ecosystems.Overall, this study provides an increased understanding of the fine scale spatial controls on CH4 flux, in particular the key role that plant cover and GPP play in enhancing CH4 emissions from tundra soils.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal and Plant Science, University of Sheffield, Western Bank, Sheffield S10 2TN UK.

ABSTRACT

Aims: Despite multiple studies investigating the environmental controls on CH4 fluxes from arctic tundra ecosystems, the high spatial variability of CH4 emissions is not fully understood. This makes the upscaling of CH4 fluxes from plot to regional scale, particularly challenging. The goal of this study is to refine our knowledge of the spatial variability and controls on CH4 emission from tundra ecosystems.

Methods: CH4 fluxes were measured in four sites across a variety of wet-sedge and tussock tundra ecosystems in Alaska using chambers and a Los Gatos CO2 and CH4 gas analyser.

Results: All sites were found to be sources of CH4, with northern sites (in Barrow) showing similar CH4 emission rates to the southernmost site (ca. 300 km south, Ivotuk). Gross primary productivity (GPP), water level and soil temperature were the most important environmental controls on CH4 emission. Greater vascular plant cover was linked with higher CH4 emission, but this increased emission with increased vascular plant cover was much higher (86 %) in the drier sites, than the wettest sites (30 %), suggesting that transport and/or substrate availability were crucial limiting factors for CH4 emission in these tundra ecosystems.

Conclusions: Overall, this study provides an increased understanding of the fine scale spatial controls on CH4 flux, in particular the key role that plant cover and GPP play in enhancing CH4 emissions from tundra soils.

No MeSH data available.