scholarly journals Attribution of spatial and temporal variations in terrestrial methane flux over North America

2010 ◽  
Vol 7 (4) ◽  
pp. 5383-5428 ◽  
Author(s):  
X. F. Xu ◽  
H. Q. Tian ◽  
C. Zhang ◽  
M. L. Liu ◽  
W. Ren ◽  
...  
Keyword(s):  
North America ◽  
Global Change ◽  
Spatial Data ◽  
Climatic Variability ◽  
Methane Flux ◽  
Temporal Variations ◽  
Spatial And Temporal Variations ◽  
Ch4 Emission ◽  
Ch4 Flux ◽  
Change Factors

Abstract. The attribution of spatial and temporal variations in terrestrial methane (CH4) flux is essential for assessing and mitigating CH4 emission from terrestrial ecosystems. In this study, we used a process-based model, the Dynamic Land Ecosystem Model (DLEM), in conjunction with spatial data of six major environmental factors to attribute the spatial and temporal variations in the terrestrial methane (CH4) flux over North America from 1979 to 2008 to six individual factors and their interaction. Over the past three decades, our simulation indicates that global change factors accumulatively contributed 43.05 Tg CH4-C (1 Tg = 1012 g) emission over North America, among which ozone (O3) pollution led to a reduced CH4 emission by 2.69 Tg CH4-C, all other factors including climate variability, nitrogen (N) deposition, rising atmospheric carbon dioxide (CO2), N fertilization, and land conversion increased terrestrial CH4 emissions by 40.37 Tg CH4-C, 0.42 Tg CH4-C, 6.95 Tg CH4-C, 0.11 Tg CH4-C, and 3.70 Tg CH4-C, respectively, and interaction between/among these global change factors led to a decline of CH4 emission by 5.80 Tg CH4-C. Climatic variability dominated the inter-annual variations in terrestrial CH4 fluxes at both continental and country levels. The relative importance of each environmental factor in determining the magnitude of methane flux shows substantially spatial variation across North America. This factorial attribution of CH4 fluxes over the North America might benefit policy makers who would like to curb climate warming by reducing CH4 emission.

scholarly journals Attribution of spatial and temporal variations in terrestrial methane flux over North America

2010 ◽  
Vol 7 (11) ◽  
pp. 3637-3655 ◽  
Author(s):  
X. F. Xu ◽  
H. Q. Tian ◽  
C. Zhang ◽  
M. L. Liu ◽  
W. Ren ◽  
...  
Keyword(s):  
North America ◽  
Global Change ◽  
Climate Variability ◽  
Spatial Data ◽  
Climatic Variability ◽  
Temporal Variations ◽  
Spatial And Temporal Variations ◽  
Ch4 Emission ◽  
Ch4 Flux ◽  
Change Factors

Abstract. The attribution of spatial and temporal variations in terrestrial methane (CH4) flux is essential for assessing and mitigating CH4 emission from terrestrial ecosystems. In this study, we used a process-based model, the Dynamic Land Ecosystem Model (DLEM), in conjunction with spatial data of six major environmental factors to attribute the spatial and temporal variations in the terrestrial methane (CH4) flux over North America from 1979 to 2008 to six individual driving factors and their interaction. Over the past three decades, our simulations indicate that global change factors accumulatively contributed 23.51 ± 9.61 T g CH4-C (1 Tg = 1012 g) emission over North America, among which ozone (O3) pollution led to a reduced CH4 emission by 2.30 ± 0.49 T g CH4-C. All other factors including climate variability, nitrogen (N) deposition, elevated atmospheric carbon dioxide (CO2), N fertilizer application, and land conversion enhanced terrestrial CH4 emissions by 19.80 ± 12.42 T g CH4-C, 0.09 ± 0.02 T g CH4-C, 6.80 ± 0.86 T g CH4-C, 0.01 ± 0.001 T g CH4-C, and 3.95 ± 0.38 T g CH4-C, respectively, and interaction between/among these global change factors led to a decline of CH4 emission by 4.84 ± 7.74 T g CH4-C. Climate variability and O3 pollution suppressed, while other factors stimulated CH4 emission over the USA; climate variability significantly enhanced, while all the other factors exerted minor effects, positive or negative, on CH4 emission in Canada; Mexico functioned as a sink for atmospheric CH4 with a major contribution from climate change. Climatic variability dominated the inter-annual variations in terrestrial CH4 flux at both continental and country levels. Precipitation played an important role in the climate-induced changes in terrestrial CH4 flux at both continental and country-levels. The relative importance of each environmental factor in determining the magnitude of CH4 flux showed substantially spatial variation across North America. This factorial attribution of CH4 flux in North America might benefit policy makers who would like to curb climate warming by reducing CH4 emission.

scholarly journals Multifactor controls on terrestrial N<sub>2</sub>O flux over North America from 1979 through 2010

2012 ◽  
Vol 9 (4) ◽  
pp. 1351-1366 ◽  
Author(s):  
X. F. Xu ◽  
H. Q. Tian ◽  
G. S. Chen ◽  
M. L. Liu ◽  
W. Ren ◽  
...  
Keyword(s):  
North America ◽  
Global Change ◽  
Climate Variability ◽  
Fertilizer Application ◽  
N2o Emission ◽  
N Deposition ◽  
N Fertilizer ◽  
Multiple Factors ◽  
Change Factors ◽  
Factor Interaction

Abstract. Nitrous oxide (N2O) is a potent greenhouse gas which also contributes to the depletion of stratospheric ozone (O3). However, the magnitude and underlying mechanisms for the spatiotemporal variations in the terrestrial sources of N2O are still far from certain. Using a process-based ecosystem model (DLEM – the Dynamic Land Ecosystem Model) driven by multiple global change factors, including climate variability, nitrogen (N) deposition, rising atmospheric carbon dioxide (CO2), tropospheric O3 pollution, N fertilizer application, and land conversion, this study examined the spatial and temporal variations in terrestrial N2O flux over North America and further attributed these variations to various driving factors. From 1979 to 2010, the North America cumulatively emitted 53.9 ± 0.9 Tg N2O-N (1 Tg = 1012 g), of which global change factors contributed 2.4 ± 0.9 Tg N2O-N, and baseline emission contributed 51.5 ± 0.6 Tg N2O-N. Climate variability, N deposition, O3 pollution, N fertilizer application, and land conversion increased N2O emission while the elevated atmospheric CO2 posed opposite effect at continental level; the interactive effect among multiple factors enhanced N2O emission over the past 32 yr. N input, including N fertilizer application in cropland and N deposition, and multi-factor interaction dominated the increases in N2O emission at continental level. At country level, N fertilizer application and multi-factor interaction made large contribution to N2O emission increase in the United States of America (USA). The climate variability dominated the increase in N2O emission from Canada. N inputs and multiple factors interaction made large contribution to the increases in N2O emission from Mexico. Central and southeastern parts of the North America – including central Canada, central USA, southeastern USA, and all of Mexico – experienced increases in N2O emission from 1979 to 2010. The fact that climate variability and multi-factor interaction largely controlled the inter-annual variations in terrestrial N2O emission at both continental and country levels indicate that projected changes in the global climate system may substantially alter the regime of N2O emission from terrestrial ecosystems during the 21st century. Our study also showed that the interactive effect among global change factors may significantly affect N2O flux, and more field experiments involving multiple factors are urgently needed.

scholarly journals Multi-year effect of wetting on CH<sub>4</sub> flux at taiga–tundra boundary in northeastern Siberia deduced from stable isotope ratios of CH<sub>4</sub>

2019 ◽  
Vol 16 (3) ◽  
pp. 755-768 ◽  
Author(s):  
Ryo Shingubara ◽  
Atsuko Sugimoto ◽  
Jun Murase ◽  
Go Iwahana ◽  
Shunsuke Tei ◽  
...  
Keyword(s):  
Water Saturation ◽  
Methane Flux ◽  
Interannual Variations ◽  
Ch4 Emission ◽  
Ch4 Flux ◽  
Ch4 Production ◽  
Year Effect ◽  
Northeastern Siberia ◽  
Order Of Magnitude ◽  
Acetoclastic Methanogenesis

Abstract. The response of CH4 emission from natural wetlands due to meteorological conditions is important because of its strong greenhouse effect. To understand the relationship between CH4 flux and wetting, we observed interannual variations in chamber CH4 flux, as well as the concentration, δ13C, and δD of dissolved CH4 during the summer from 2009 to 2013 at the taiga–tundra boundary in the vicinity of Chokurdakh (70∘37′ N, 147∘55′ E), located on the lowlands of the Indigirka River in northeastern Siberia. We also conducted soil incubation experiments to interpret δ13C and δD of dissolved CH4 and to investigate variations in CH4 production and oxidation processes. Methane flux showed large interannual variations in wet areas of sphagnum mosses and sedges (36–140 mg CH4 m−2 day−1 emitted). Increased CH4 emission was recorded in the summer of 2011 when a wetting event with extreme precipitation occurred. Although water level decreased from 2011 to 2013, CH4 emission remained relatively high in 2012, and increased further in 2013. Thaw depth became deeper from 2011 to 2013, which may partly explain the increase in CH4 emission. Moreover, dissolved CH4 concentration rose sharply by 1 order of magnitude from 2011 to 2012, and increased further from 2012 to 2013. Large variations in δ13C and δD of dissolved CH4 were observed in 2011, and smaller variations were seen in 2012 and 2013, suggesting both enhancement of CH4 production and less significance of CH4 oxidation relative to the larger pool of dissolved CH4. These multi-year effects of wetting on CH4 dynamics may have been caused by continued soil reduction across multiple years following the wetting. Delayed activation of acetoclastic methanogenesis following soil reduction could also have contributed to the enhancement of CH4 production. These processes suggest that duration of water saturation in the active layer can be important for predicting CH4 emission following a wetting event in the permafrost ecosystem.

scholarly journals Impact of land use and soil properties on soil methane flux response to biochar addition

2017 ◽  
Author(s):  
Weiwei Cong ◽  
Jun Meng ◽  
Samantha C. Ying
Keyword(s):  
Land Use ◽  
Soil Properties ◽  
Total Nitrogen ◽  
Additive Model ◽  
Methane Flux ◽  
Paddy Soils ◽  
Ch4 Emission ◽  
Ch4 Flux ◽  
Linear Additive Model ◽  
The Impact

Abstract. Addition of biochar to soils has been shown to increase crop yield and aid in mitigating greenhouse gas emissions by decreasing the extent of soil methane (CH4) flux. Previous studies utilizing metaanalysis to better understand the impact of environmental and management factors on CH4 flux from biochar treated soil systems have provided contrasting results, ranging from significant increase, decrease, to no change in methane flux after amendment. We hypothesized that these discrepancies could be explained by separating studies into two major land use categories, upland and paddy, prior to analysis so that the overall redox conditions are more comparable across studies upon which statistical comparisons are made. Furthermore, past studies did not consider potentially critical soil properties including soil organic carbon, total nitrogen, C/N, and soil texture; a number of biochar properties including biochar pH and C/N; and five additional management and experimental factors. In this study, Hedge's d metric was calculated and Wilcoxon analyses were used in a meta-analysis to determine the impact of these additional factors on methane flux from biochar-amended upland versus paddy soils. We demonstrate that variations in soil characteristics including SOC, C/N, and pH significantly influences the methane flux from biochar treated soils, while biochar characteristics and management practices have less to no effect as determined by the magnitude of the Hedge's d metric. Soils with low SOC, total nitrogen, C/N, acidic or alkaline pH exhibited lowest CH4 emission rates/highest CH4 uptake rates, whereas soils with higher SOC content, C/N, and circumneutral pH exhibited higher CH4 emission with biochar addition. Several possible mechanisms are suggested to explain the role of these variables in CH4 cycling. Results from this study will be used to evaluate the input parameters for building a linear additive model to quantitatively predict soil methane flux in response to biochar additions. Ultimately, implementation of the linear additive model can be extremely valuable for advising agricultural practices toward minimize methane emissions or maximizing methane sink strength. We suggest that additional field and controlled experiments be performed to better define the reaction network that controls methane flux from biochar treated soils, with particular attention to paddy soils where studies are still lacking.

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