scholarly journals Growing season CH<sub>4</sub> and N<sub>2</sub>O fluxes from a sub-arctic landscape in northern Finland

2016 ◽  
Author(s):  
Kerry J. Dinsmore ◽  
Julia Drewer ◽  
Peter E. Levy ◽  
Charles George ◽  
Annalea Lohila ◽  
...  
Keyword(s):  
Spectral Data ◽  
Temporal Variability ◽  
Radiative Forcing ◽  
Growing Season ◽  
Spatial And Temporal Variability ◽  
N2o Emissions ◽  
Feedback Mechanisms ◽  
Ch4 And N2o ◽  
Subarctic Forest ◽  
Chamber Measurements

Abstract. Subarctic and boreal emissions of CH4 are important contributors to the atmospheric greenhouse gas (GHG) balance and subsequently the global radiative forcing. Whilst N2O emissions may be lower, the much greater radiative forcing they produce justifies their inclusion in GHG studies. In addition to the quantification of flux magnitude, it is essential that we understand the drivers of emissions to be able to accurately predict climate-driven changes and potential feedback mechanisms. Hence this study aims to increase our understanding of what drives fluxes of CH4 and N2O in a subarctic forest/wetland landscape, exploring both spatial and temporal variability, and uses satellite derived spectral data to extrapolate from chamber scale fluxes to a 2 × 2 km landscape area. From static chamber measurements made during summer and autumn campaigns in 2012 in the Sodankylä region of Northern Finland, we concluded that wetlands represent a significant source of CH4 (3.35 ± 0.44 mg C m−2 h−1 during summer campaign and 0.62 ± 0.09 mg C m−2 h−1 during autumn campaign), whilst the surrounding forests represent a small sink (−0.06 ± 

Spatial and temporal variability of soil respiration in agricultural fields

1991 ◽  
Vol 71 (2) ◽  
pp. 189-196 ◽  
Author(s):  
P. Rochette ◽  
R. L. Desjardins ◽  
E. Pattey
Keyword(s):  
Soil Respiration ◽  
Temporal Variability ◽  
Growing Season ◽  
Bare Soil ◽  
Wheat Crop ◽  
Soil Conditions ◽  
Spatial And Temporal Variability ◽  
Maize Crop ◽  
Significant Difference ◽  
Chamber Measurements

Chamber measurements of CO2 evolution were made on bare soil, and in maize (1988) and wheat (1989) crops in order to study the spatial and temporal variability of soil respiration (Rsoil). Semivariograms showed no definite structure of spatial autocorrelation on bare soil when measurements were made along transects. Spatial variability was shown to occur at a scale smaller than 15 cm. In a maize crop, Rsoil in the row was significantly higher (P = 0.05) than in the interrow when the soil surface was dry. Under wet soil conditions, Rsoil in the interrow compacted by the tractor wheel was lower (P = 0.05) than on noncompacted soil and no significant difference was found between rows and interrows. These observations were attributed to the contribution of plant roots to Rsoil in dry conditions. In wetter soil, the role of microbial activity was dominant except in the compacted interrow where lower airfilled porosity caused lower Rsoil. Random measurements in a wheat crop over the growing season showed that the number of samples needed to estimate the Rsoil of a 1 ha area within 10% (P = 0.05) of its mean value decreased from 190 at the time of seeding to 30 at the end of the season. The maximum Rsoil during the growing season coincided with the period of maximum growth of both crops. A post-rainfall Rsoil burst is also described. Immediately after a 2-h rainfall event, when soil was at field capacity, Rsoil was nine times higher than its level prior to the rainfall and gradually decreased with time. Key words: Soil respiration, variability, chamber measurements, CO2 flux

scholarly journals Growing season CH<sub>4</sub> and N<sub>2</sub>O fluxes from a subarctic landscape in northern Finland; from chamber to landscape scale

2017 ◽  
Vol 14 (4) ◽  
pp. 799-815 ◽  
Author(s):  
Kerry J. Dinsmore ◽  
Julia Drewer ◽  
Peter E. Levy ◽  
Charles George ◽  
Annalea Lohila ◽  
...  
Keyword(s):  
Spectral Data ◽  
Water Table ◽  
Radiative Forcing ◽  
Landscape Scale ◽  
Spatial And Temporal Variability ◽  
N2o Emissions ◽  
Small Magnitude ◽  
Image Domain ◽  
Ch4 Emissions ◽  
N2o Fluxes

Abstract. Subarctic and boreal emissions of CH4 are important contributors to the atmospheric greenhouse gas (GHG) balance and subsequently the global radiative forcing. Whilst N2O emissions may be lower, the much greater radiative forcing they produce justifies their inclusion in GHG studies. In addition to the quantification of flux magnitude, it is essential that we understand the drivers of emissions to be able to accurately predict climate-driven changes and potential feedback mechanisms. Hence this study aims to increase our understanding of what drives fluxes of CH4 and N2O in a subarctic forest/wetland landscape during peak summer conditions and into the shoulder season, exploring both spatial and temporal variability, and uses satellite-derived spectral data to extrapolate from chamber-scale fluxes to a 2 km  ×  2 km landscape area.From static chamber measurements made during summer and autumn campaigns in 2012 in the Sodankylä region of northern Finland, we concluded that wetlands represent a significant source of CH4 (3.35 ± 0.44 mg C m−2 h−1 during the summer campaign and 0.62 ± 0.09 mg C m−2 h−1 during the autumn campaign), whilst the surrounding forests represent a small sink (−0.06 ± < 0.01 mg C m−2 h−1 during the summer campaign and −0.03 ± < 0.01 mg C m−2 h−1 during the autumn campaign). N2O fluxes were near-zero across both ecosystems.We found a weak negative relationship between CH4 emissions and water table depth in the wetland, with emissions decreasing as the water table approached and flooded the soil surface and a positive relationship between CH4 emissions and the presence of Sphagnum mosses. Temperature was also an important driver of CH4 with emissions increasing to a peak at approximately 12 °C. Little could be determined about the drivers of N2O emissions given the small magnitude of the fluxes.A multiple regression modelling approach was used to describe CH4 emissions based on spectral data from PLEIADES PA1 satellite imagery across a 2 km  ×  2 km landscape. When applied across the whole image domain we calculated a CH4 source of 2.05 ± 0.61 mg C m−2 h−1. This was significantly higher than landscape estimates based on either a simple mean or weighted by forest/wetland proportion (0.99 ± 0.16, 0.93 ± 0.12 mg C m−2 h−1, respectively). Hence we conclude that ignoring the detailed spatial variability in CH4 emissions within a landscape leads to a potentially significant underestimation of landscape-scale fluxes. Given the small magnitude of measured N2O fluxes a similar level of detailed upscaling was not needed; we conclude that N2O fluxes do not currently comprise an important component of the landscape-scale GHG budget at this site.

scholarly journals Estimation of the aerosol radiative forcing at ground level, over land, and in cloudless atmosphere, from METEOSAT-7 observation: method and case study

2008 ◽  
Vol 8 (3) ◽  
pp. 625-636 ◽  
Author(s):  
T. Elias ◽  
J.-L. Roujean
Keyword(s):  
Optical Thickness ◽  
Temporal Variability ◽  
Radiative Forcing ◽  
Ground Level ◽  
Aerosol Optical Thickness ◽  
Reference Level ◽  
Urban Site ◽  
Spatial And Temporal Variability ◽  
Aerosol Radiative Forcing ◽  
Aerosol Radiative

Abstract. A new method is proposed to estimate the spatial and temporal variability of the solar radiative flux reaching the surface over land (DSSF), as well as the Aerosol Radiative Forcing (ARF), in cloud-free atmosphere. The objective of regional applications of the method is attainable by using the visible broadband of METEOSAT-7 satellite instrument which scans Europe and Africa on a half-hourly basis. The method relies on a selection of best correspondence between METEOSAT-7 radiance and radiative transfer computations. The validation of DSSF is performed comparing retrievals with ground-based measurements acquired in two contrasted environments: an urban site near Paris and a continental background site located South East of France. The study is concentrated on aerosol episodes occurring around the 2003 summer heat wave, providing 42 cases of comparison for variable solar zenith angle (from 59° to 69°), variable aerosol type (biomass burning emissions and urban pollution), and variable aerosol optical thickness (a factor 6 in magnitude). The method reproduces measurements of DSSF within an accuracy assessment of 20 W m−2 (5% in relative) in 70% of the situations, and within 40 W m−2 in 90% of the situations, for the two case studies considered here. Considering aerosol is the main contributor in changing the measured radiance at the top of the atmosphere, DSSF temporal variability is assumed to be caused only by aerosols, and consequently ARF at ground level and over land is also retrieved: ARF is computed as the difference between DSSF and a parameterised aerosol-free reference level. Retrievals are linearly correlated with the ground-based measurements of the aerosol optical thickness (AOT): sensitivity is included between 120 and 160 W m−2 per unity of AOT at 440 nm. AOT being an instantaneous measure indicative of the aerosol columnar amount, we prove the feasibility to infer instantaneous aerosol radiative impact at the ground level over land with METEOSAT-7 visible channel.

scholarly journals Greenhouse Gas Emissions from the Tibetan Alpine Grassland: Effects of Nitrogen and Phosphorus Addition

2018 ◽  
Vol 10 (12) ◽  
pp. 4454
Author(s):  
Guangshuai Wang ◽  
Yueping Liang ◽  
Fei Ren ◽  
Xiaoxia Yang ◽  
Zhaorong Mi ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Greenhouse Gas ◽  
Interactive Effect ◽  
Co2 Flux ◽  
Growing Season ◽  
N2o Emissions ◽  
The Tibetan Plateau ◽  
Nitrogen And Phosphorus ◽  
Annual Budget ◽  
Ch4 And N2o

The cycle of key nutrient elements nitrogen (N) and phosphorus (P) has been massively altered by anthropogenic activities. Little is known about the impacts on greenhouse gas (GHG) emission of the large nutrient additions occurring in the alpine grasslands of the Tibetan Plateau. We investigated soil surface emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) under control, N, P and combined nitrogen and phosphorus (NP) additions from July 2011 to September 2012. Compared to the control, CO2 flux significantly increased by 14.6% and 27.4% following P and NP addition, respectively. The interaction of NP addition had a significant influence on CO2 flux during the non-growing season and the spring thaw period. Compared to the control, CH4 flux decreased by 9.9%, 23.2% and 26.7% following N, P and NP additions, respectively, and no interactive effect of NP addition was found in any period. Soil N2O flux was significantly increased 2.6 fold and 3.3 fold, following N and NP addition treatments, respectively, and there was no interaction effect of NP addition together. The contribution of cumulative CO2 emission during the non-growing season was less than 20% of the annual budget, but cumulative CH4 and N2O emissions during the same period can account for 37.3–48.9% and 44.7–59.5% of the annual budget, respectively. Methane and N2O emissions did not increase greatly during the spring thawing period, with contributions of only 0.4–3.6% and 10.3–12.3% of the annual budget, respectively. Our results suggest that N and P addition could increase CO2 and N2O emissions and reduce CH4 emission. Furthermore, although the non-growing season is very cold and long, cumulative CH4 and N2O emissions are considerable during this period and cannot be neglected by future studies evaluating the greenhouse gas emission budget in the Tibetan plateau.

scholarly journals Soybean yield estimation by an agrometeorological model in a GIS

2003 ◽  
Vol 60 (3) ◽  
pp. 433-440 ◽  
Author(s):  
Luciana Miura Sugawara Berka ◽  
Bernardo Friedrich Theodor Rudorff ◽  
Yosio Edemir Shimabukuro
Keyword(s):  
Information System ◽  
Crop Yield ◽  
Temporal Variability ◽  
Meteorological Data ◽  
Maximum Yield ◽  
Growing Season ◽  
The State ◽  
Spatial And Temporal Variability ◽  
Department Of Agriculture ◽  
Glycine Max L

Agrometeorological models interfaced with the Geographic Information System - GIS are an alternative to simulate and quantify the effect of weather spatial and temporal variability on crop yield. The objective of this work was to adapt and interface an agrometeorological model with a GIS to estimate soybean [Glycine max (L.) Merr.] yield. Yield estimates were generated for 144 municipalities in the State of Paraná, Brazil, responsible for 90% of the soybean production in the State, from 1996/1997 to 2000/2001. The model uses agronomical parameters and meteorological data to calculate maximum yield which will be penalized under drought stress. Comparative analyses between the yield estimated by the model and that reported by the Paraná State Department of Agriculture (SEAB) were performed using the "t" test for paired observations. For the 1996/1997 year the model overestimated yield by 10.8%, which may be attributed to the occurrence of fungal diseases not considered by the model. For 1997/1998, 1998/1999 and 1999/2000 no differences (P > 0.05) were found between the yield estimated by the model and SEAB's data. For 2000/2001 the model underestimated yield by 10.5% and the cause for this difference needs further investigation. The model interfaced with a GIS is an useful tool to monitor soybean crop during growing season to estimate crop yield.

scholarly journals Carbon Sequestration and Contribution of CO2, CH4 and N2O Fluxes to Global Warming Potential from Paddy-Fallow Fields on Mineral Soil Beneath Peat in Central Hokkaido, Japan

Agriculture ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 6 ◽  
Author(s):  
Habib Mohammad Naser ◽  
Osamu Nagata ◽  
Sarmin Sultana ◽  
Ryusuke Hatano
Keyword(s):  
Global Warming ◽  
Carbon Sequestration ◽  
Growing Season ◽  
Rice Paddy ◽  
Paddy Fields ◽  
N2o Emissions ◽  
Growing Period ◽  
N2o Fluxes ◽  
Ch4 And N2o ◽  
Winter Fallow

Since each greenhouse gas (GHG) has its own radiative capacity, all three gasses (CO2, CH4 and N2O) must be accounted for by calculating the net global warming potential (GWP) in a crop production system. To compare the impact of GHG fluxes from the rice growing and the fallow season on the annual gas fluxes, and their contribution to the GWP and carbon sequestration (CS) were evaluated. From May to April in Bibai (43°18′ N, 141°44′ E), in central Hokkaido, Japan, three rice paddy fields under actual management conditions were investigated to determine CS and the contribution of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes to GWP. Methane and N2O fluxes were measured by placing the chamber over the rice plants covering four hills and CO2 fluxes from rice plants root free space in paddy fields were taken as an indicator of soil microbial respiration (Rm) using the closed chamber method. Soil CS was calculated as the difference between net primary production (NPP) and loss of carbon (C) through Rm, emission of CH4 and harvest of crop C. Annual cumulative Rm ranged from 422 to 519 g C m−2 yr−1; which accounted for 54.7 to 55.5% of the rice growing season in particular. Annual cumulative CH4 emissions ranged from 75.5 to 116 g C m−2 yr−1 and this contribution occurred entirely during the rice growing period. Total cumulative N2O emissions ranged from 0.091 to 0.154 g N m−2 yr−1 and from 73.5 to 81.3% of the total N2O emissions recorded during the winter-fallow season. The CS ranged from −305 to −365 g C m−2 yr−1, suggesting that C input by NPP may not be compensate for the loss of soil C. The loss of C in the winter-fallow season was much higher (62 to 66%) than in the growing season. The annual net GWP from the investigated paddy fields ranged from 3823 to 5016 g CO2 equivalent m−2 yr−1. Annual GWPCH4 accounted for 71.9 to 86.1% of the annual net GWP predominantly from the rice growing period. These results indicate that CH4 dominated the net GWP of the rice paddy.

scholarly journals Aircraft observations since the 1990s reveal increases of tropospheric ozone at multiple locations across the Northern Hemisphere

2020 ◽  
Vol 6 (34) ◽  
pp. eaba8272 ◽  
Author(s):  
Audrey Gaudel ◽  
Owen R. Cooper ◽  
Kai-Lan Chang ◽  
Ilann Bourgeois ◽  
Jerry R. Ziemke ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Temporal Variability ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Monitoring Network ◽  
Spatial And Temporal Variability ◽  
Commercial Aircraft ◽  
Aircraft Observations ◽  
Ozone Precursor ◽  
Satellite Product

Tropospheric ozone is an important greenhouse gas, is detrimental to human health and crop and ecosystem productivity, and controls the oxidizing capacity of the troposphere. Because of its high spatial and temporal variability and limited observations, quantifying net tropospheric ozone changes across the Northern Hemisphere on time scales of two decades had not been possible. Here, we show, using newly available observations from an extensive commercial aircraft monitoring network, that tropospheric ozone has increased above 11 regions of the Northern Hemisphere since the mid-1990s, consistent with the OMI/MLS satellite product. The net result of shifting anthropogenic ozone precursor emissions has led to an increase of ozone and its radiative forcing above all 11 study regions of the Northern Hemisphere, despite NOx emission reductions at midlatitudes.

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