scholarly journals Impacts of a decadal drainage disturbance on surface–atmosphere fluxes of carbon dioxide in a permafrost ecosystem

2016 ◽  
Vol 13 (18) ◽  
pp. 5315-5332 ◽  
Author(s):  
Fanny Kittler ◽  
Ina Burjack ◽  
Chiara A. R. Corradi ◽  
Martin Heimann ◽  
Olaf Kolle ◽  
...  
Keyword(s):  
Co2 Flux ◽  
Growing Season ◽  
Co2 Exchange ◽  
Ecosystem Structure ◽  
Co2 Fluxes ◽  
Near Surface ◽  
The Past ◽  
Tundra Ecosystem ◽  
Tussock Tundra ◽  
Hydrologic Conditions

Abstract. Hydrologic conditions are a major controlling factor for carbon exchange processes in high-latitude ecosystems. The presence or absence of water-logged conditions can lead to significant shifts in ecosystem structure and carbon cycle processes. In this study, we compared growing season CO2 fluxes of a wet tussock tundra ecosystem from an area affected by decadal drainage to an undisturbed area on the Kolyma floodplain in northeastern Siberia. For this comparison we found the sink strength for CO2 in recent years (2013–2015) to be systematically reduced within the drained area, with a minor increase in photosynthetic uptake due to a higher abundance of shrubs outweighed by a more pronounced increase in respiration due to warmer near-surface soil layers. Still, in comparison to the strong reduction of fluxes immediately following the drainage disturbance in 2005, recent CO2 exchange with the atmosphere over this disturbed part of the tundra indicate a higher carbon turnover, and a seasonal amplitude that is comparable again to that within the control section. This indicates that the local permafrost ecosystem is capable of adapting to significantly different hydrologic conditions without losing its capacity to act as a net sink for CO2 over the growing season. The comparison of undisturbed CO2 flux rates from 2013–2015 to the period of 2002–2004 indicates that CO2 exchange with the atmosphere was intensified, with increased component fluxes (ecosystem respiration and gross primary production) over the past decade. Net changes in CO2 fluxes are dominated by a major increase in photosynthetic uptake, resulting in a stronger CO2 sink in 2013–2015. Application of a MODIS-based classification scheme to separate the growing season into four sub-seasons improved the interpretation of interannual variability by illustrating the systematic shifts in CO2 uptake patterns that have occurred in this ecosystem over the past 10 years and highlighting the important role of the late growing season for net CO2 flux budgets.

scholarly journals Impacts of a decadal drainage disturbance on surface–atmosphere fluxes of carbon dioxide in a permafrost ecosystem

2016 ◽  
Author(s):  
F. Kittler ◽  
I. Burjack ◽  
C. A. R. Corradi ◽  
M. Heimann ◽  
O. Kolle ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Growing Season ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
Ecosystem Structure ◽  
Near Surface ◽  
The Past ◽  
Tundra Ecosystem ◽  
Tussock Tundra ◽  
Hydrologic Conditions

Abstract. Hydrologic conditions are a major controlling factor for carbon exchange processes in high-latitude ecosystems. The presence or absence of water-logged conditions can lead to significant shifts in ecosystem structure and carbon cycle processes. In this study, we compared growing season CO2 fluxes of a wet tussock tundra ecosystem from an area affected by decadal drainage and an undisturbed area on the Kolyma floodplain in northeastern Siberia. For this comparison we found the CO2 uptake to be systematically reduced within the drained area, with a minor increase in photosynthetic uptake due to a higher abundance of shrubs outweighed by a more pronounced increase in respiration due to warmer near-surface soil layers. Carbon dioxide exchange with the atmosphere over this disturbed part of the tundra has rebounded from the strong reduction of fluxes immediately following the drainage disturbance in 2005. This indicates that the local permafrost ecosystem is capable of adapting to significantly different hydrologic conditions without losing its capacity to act as a net sink for CO2 over the growing season. The comparison of undisturbed CO2 flux rates from 2013–2015 to the period of 2002–2004 indicates that overall CO2 exchange with the atmosphere was intensified. Analyzing trends in component fluxes (ecosystem respiration and gross primary production) over the past decade, we found that net changes in CO2 exchange fluxes are dominated by a major increase in photosynthetic uptake, resulting in a stronger CO2 sink in 2013–2015. Application of a MODIS-based classification scheme to separate the growing season into four sub-seasons improved the interpretation of interannual variability, and helps in illustrating the systematic shifts in CO2 uptake patterns that have occurred in this ecosystem over the past 10 years.

scholarly journals Experimental warming differentially affects vegetative and reproductive phenology of tundra plants

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Courtney G. Collins ◽  
Sarah C. Elmendorf ◽  
Robert D. Hollister ◽  
Greg H. R. Henry ◽  
Karin Clark ◽  
...  
Keyword(s):  
Growing Season ◽  
Plant Phenology ◽  
Reproductive Phenology ◽  
Ecosystem Structure ◽  
Experimental Warming ◽  
Growing Seasons ◽  
Tundra Ecosystem ◽  
Phenological Shifts ◽  
And Function ◽  
Ecosystem Structure And Function

AbstractRapid climate warming is altering Arctic and alpine tundra ecosystem structure and function, including shifts in plant phenology. While the advancement of green up and flowering are well-documented, it remains unclear whether all phenophases, particularly those later in the season, will shift in unison or respond divergently to warming. Here, we present the largest synthesis to our knowledge of experimental warming effects on tundra plant phenology from the International Tundra Experiment. We examine the effect of warming on a suite of season-wide plant phenophases. Results challenge the expectation that all phenophases will advance in unison to warming. Instead, we find that experimental warming caused: (1) larger phenological shifts in reproductive versus vegetative phenophases and (2) advanced reproductive phenophases and green up but delayed leaf senescence which translated to a lengthening of the growing season by approximately 3%. Patterns were consistent across sites, plant species and over time. The advancement of reproductive seasons and lengthening of growing seasons may have significant consequences for trophic interactions and ecosystem function across the tundra.

scholarly journals O<sub>2</sub> : CO<sub>2</sub> exchange ratio for net turbulent flux observed in an urban area of Tokyo, Japan, and its application to an evaluation of anthropogenic CO<sub>2</sub> emissions

2020 ◽  
Vol 20 (9) ◽  
pp. 5293-5308
Author(s):  
Shigeyuki Ishidoya ◽  
Hirofumi Sugawara ◽  
Yukio Terao ◽  
Naoki Kaneyasu ◽  
Nobuyuki Aoki ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Urban Area ◽  
Co2 Emission ◽  
Co2 Flux ◽  
Co2 Exchange ◽  
Co2 Fluxes ◽  
Diurnal Cycles ◽  
Co2 Concentrations ◽  
Human Respiration ◽  
Two Peaks

Abstract. In order to examine O2 consumption and CO2 emission in a megacity, continuous observations of atmospheric O2 and CO2 concentrations, along with CO2 flux, have been carried out simultaneously since March 2016 at the Yoyogi (YYG) site located in the middle of Tokyo, Japan. An average O2 : CO2 exchange ratio for net turbulent O2 and CO2 fluxes (ORF) between the urban area and the overlaying atmosphere was obtained based on an aerodynamic method using the observed O2 and CO2 concentrations. The yearly mean ORF was found to be 1.62, falling within the range of the average OR values of liquid and gas fuels, and the annual average daily mean O2 flux at YYG was estimated to be −16.3 µmol m−2 s−1 based on the ORF and CO2 flux. By using the observed ORF and CO2 flux, along with the inventory-based CO2 emission from human respiration, we estimated the average diurnal cycles of CO2 fluxes from gas and liquid fuel consumption separately for each season. Both the estimated and inventory-based CO2 fluxes from gas fuel consumption showed average diurnal cycles with two peaks, one in the morning and another one in the evening; however, the evening peak of the inventory-based gas consumption was much larger than that estimated from the CO2 flux. This can explain the discrepancy between the observed and inventory-based total CO2 fluxes at YYG. Therefore, simultaneous observations of ORF and CO2 flux are useful in validating CO2 emission inventories from statistical data.

scholarly journals Partitioning net ecosystem exchange of CO<sub>2</sub> on the pedon scale in the Lena River Delta, Siberia

2019 ◽  
Vol 16 (7) ◽  
pp. 1543-1562 ◽  
Author(s):  
Tim Eckhardt ◽  
Christian Knoblauch ◽  
Lars Kutzbach ◽  
David Holl ◽  
Gillian Simpson ◽  
...  
Keyword(s):  
Growing Season ◽  
Arctic Tundra ◽  
River Delta ◽  
Environmental Drivers ◽  
Co2 Fluxes ◽  
Lena River ◽  
Hydrological Conditions ◽  
Tundra Ecosystem ◽  
Water Saturated ◽  
Lena River Delta

Abstract. Arctic tundra ecosystems are currently facing amplified rates of climate warming. Since these ecosystems store significant amounts of soil organic carbon, which can be mineralized to carbon dioxide (CO2) and methane (CH4), rising temperatures may cause increasing greenhouse gas fluxes to the atmosphere. To understand how net the ecosystem exchange (NEE) of CO2 will respond to changing climatic and environmental conditions, it is necessary to understand the individual responses of the processes contributing to NEE. Therefore, this study aimed to partition NEE at the soil–plant–atmosphere interface in an arctic tundra ecosystem and to identify the main environmental drivers of these fluxes. NEE was partitioned into gross primary productivity (GPP) and ecosystem respiration (Reco) and further into autotrophic (RA) and heterotrophic respiration (RH). The study examined CO2 flux data collected during the growing season in 2015 using closed-chamber measurements in a polygonal tundra landscape in the Lena River Delta, northeastern Siberia. To capture the influence of soil hydrology on CO2 fluxes, measurements were conducted at a water-saturated polygon center and a well-drained polygon rim. These chamber-measured fluxes were used to model NEE, GPP, Reco, RH, RA, and net primary production (NPP) at the pedon scale (1–10 m) and to determine cumulative growing season fluxes. Here, the response of in situ measured RA and RH fluxes from permafrost-affected soils of the polygonal tundra to hydrological conditions have been examined. Although changes in the water table depth at the polygon center sites did not affect CO2 fluxes from RH, rising water tables were linked to reduced CO2 fluxes from RA. Furthermore, this work found the polygonal tundra in the Lena River Delta to be a net sink for atmospheric CO2 during the growing season. The NEE at the wet, depressed polygon center was more than twice that at the drier polygon rim. These differences between the two sites were caused by higher GPP fluxes due to a higher vascular plant density and lower Reco fluxes due to oxygen limitation under water-saturated conditions at the polygon center in comparison to the rim. Hence, soil hydrological conditions were one of the key drivers for the different CO2 fluxes across this highly heterogeneous tundra landscape.

scholarly journals Ecosystem responses to elevated CO<sub>2</sub> using airborne remote sensing at Mammoth Mountain, California

2018 ◽  
Author(s):  
Kerry Cawse-Nicholson ◽  
Joshua B. Fisher ◽  
Caroline A. Famiglietti ◽  
Amy Braverman ◽  
Florian M. Schwandner ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Co2 Emissions ◽  
Elevated Co2 ◽  
Co2 Flux ◽  
Ecosystem Structure ◽  
Co2 Fluxes ◽  
Soil Co2 ◽  
Ecosystem Responses ◽  
Mammoth Mountain ◽  
And Function

Abstract. We present an exploratory study examining the use of airborne remote sensing observations to detect ecological responses to elevated CO2 emissions from active volcanic systems. To evaluate these ecosystem responses, existing spectroscopic, thermal, and lidar data acquired over forest ecosystems on Mammoth Mountain volcano, California, were exploited, along with in situ measurements of volcanic soil CO2 fluxes. The elevated CO2 response was used to statistically model ecosystem structure, composition and function, evaluated via data products including biomass, plant foliar traits and vegetation indices, and evapotranspiration (ET). Using regression ensemble models, we found that soil CO2 flux was a significant predictor for ecological variables, including Normalized Vegetation Difference Index (NDVI), canopy nitrogen, ET, and biomass. Additionally, the relationships between ecological variables changed with increasingly elevated (volcanically influenced) over non-volcanic background soil CO2 fluxes, suggesting a shift in coupling/decoupling among ecosystem structure, composition, and function synergies. For example, ET and biomass were significantly correlated for areas without elevated CO2 flux, but decoupled with elevated CO2 flux. This study demonstrates that a) volcanic systems show great potential as a means to study the properties of ecosystems and their responses to elevated CO2 emissions and b) these ecosystem responses are measureable using a suite of airborne remotely sensed data.

scholarly journals Consumption of atmospheric O<sub>2</sub> in an Urban Area of Tokyo, Japan derived from continuous observations of O<sub>2</sub> and CO<sub>2</sub> concentrations and CO<sub>2</sub> flux

2019 ◽  
Author(s):  
Shigeyuki Ishidoya ◽  
Hirofumi Sugawara ◽  
Yukio Terao ◽  
Naoki Kaneyasu ◽  
Nobuyuki Aoki ◽  
...  
Keyword(s):  
Urban Area ◽  
Consumption Rate ◽  
Co2 Flux ◽  
Co2 Exchange ◽  
O2 Consumption ◽  
Co2 Fluxes ◽  
Aerodynamic Method ◽  
Co2 Concentrations ◽  
Global Mean

Abstract. In order to estimate the atmospheric O2 consumption in a megacity, continuous observations of atmospheric O2 and CO2 concentrations and of CO2 flux have been carried out simultaneously at the Yoyogi (YYG) site in middle of Tokyo, Japan since March 2016. An average O2 : CO2 exchange ratio for net turbulent O2 and CO2 fluxes (ORF) between the urban area and the overlying atmosphere was obtained based on an aerodynamic method using the observed O2 and CO2 concentrations. The yearly mean ORF was found to be 1.62, falling within the range of the average OR values of liquid and gas fuels. Seasonally different diurnal ORF cycles at YYG indicated that the consumption of gas fuels was larger in the winter than that in the summer, especially in the morning and late in the evening. By using the ORF and CO2 flux values, the annual mean O2 consumption rate was estimated to be −16.3 μmol m−2 s−1, which is more than 350 times larger than the global mean atmospheric O2 consumption rate (about −4 μmol yr−1), implying that our life in a megacity is far from sustainable from a viewpoint of the conservation of atmospheric O2.

scholarly journals Coupled eco-hydrology and biogeochemistry algorithms enable the simulation of water table depth effects on boreal peatland net CO<sub>2</sub> exchange

2017 ◽  
Vol 14 (23) ◽  
pp. 5507-5531 ◽  
Author(s):  
Mohammad Mezbahuddin ◽  
Robert F. Grant ◽  
Lawrence B. Flanagan
Keyword(s):  
Plant Growth ◽  
Water Table ◽  
Oxygen Transport ◽  
Vascular Plant ◽  
Co2 Exchange ◽  
Water Table Depth ◽  
Co2 Fluxes ◽  
Net Ecosystem Co2 Exchange ◽  
Predictive Capacity ◽  
Near Surface

Abstract. Water table depth (WTD) effects on net ecosystem CO2 exchange of boreal peatlands are largely mediated by hydrological effects on peat biogeochemistry and the ecophysiology of peatland vegetation. The lack of representation of these effects in carbon models currently limits our predictive capacity for changes in boreal peatland carbon deposits under potential future drier and warmer climates. We examined whether a process-level coupling of a prognostic WTD with (1) oxygen transport, which controls energy yields from microbial and root oxidation–reduction reactions, and (2) vascular and nonvascular plant water relations could explain mechanisms that control variations in net CO2 exchange of a boreal fen under contrasting WTD conditions, i.e., shallow vs. deep WTD. Such coupling of eco-hydrology and biogeochemistry algorithms in a process-based ecosystem model, ecosys, was tested against net ecosystem CO2 exchange measurements in a western Canadian boreal fen peatland over a period of drier-weather-driven gradual WTD drawdown. A May–October WTD drawdown of  ∼  0.25 m from 2004 to 2009 hastened oxygen transport to microbial and root surfaces, enabling greater microbial and root energy yields and peat and litter decomposition, which raised modeled ecosystem respiration (Re) by 0.26 µmol CO2 m−2 s−1 per 0.1 m of WTD drawdown. It also augmented nutrient mineralization, and hence root nutrient availability and uptake, which resulted in improved leaf nutrient (nitrogen) status that facilitated carboxylation and raised modeled vascular gross primary productivity (GPP) and plant growth. The increase in modeled vascular GPP exceeded declines in modeled nonvascular (moss) GPP due to greater shading from increased vascular plant growth and moss drying from near-surface peat desiccation, thereby causing a net increase in modeled growing season GPP by 0.39 µmol CO2 m−2 s−1 per 0.1 m of WTD drawdown. Similar increases in GPP and Re caused no significant WTD effects on modeled seasonal and interannual variations in net ecosystem productivity (NEP). These modeled trends were corroborated well by eddy covariance measured hourly net CO2 fluxes (modeled vs. measured: R2  ∼  0.8, slopes  ∼ 1 ± 0.1, intercepts  ∼ 0.05 µmol m−2 s−1), hourly measured automated chamber net CO2 fluxes (modeled vs. measured: R2  ∼ 0.7, slopes  ∼ 1 ± 0.1, intercepts  ∼ 0.4 µmol m−2 s−1), and other biometric and laboratory measurements. Modeled drainage as an analog for WTD drawdown induced by climate-change-driven drying showed that this boreal peatland would switch from a large carbon sink (NEP  ∼  160 g C m−2 yr−1) to carbon neutrality (NEP  ∼  10 g C m−2 yr−1) should the water table deepen by a further  ∼ 0.5 m. This decline in projected NEP indicated that a further WTD drawdown at this fen would eventually lead to a decline in GPP due to water limitation. Therefore, representing the effects of interactions among hydrology, biogeochemistry and plant physiological ecology on ecosystem carbon, water, and nutrient cycling in global carbon models would improve our predictive capacity for changes in boreal peatland carbon sequestration under changing climates.

scholarly journals Net CO2 Budget and Seasonal Variation of CO2 Fluxes at a Wet Sedge Tundra Ecosystem at Barrow, Alaska during the 2000 Growing Season

2003 ◽  
Vol 59 (2) ◽  
pp. 141-154 ◽  
Author(s):  
Masayoshi MANO ◽  
Yoshinobu HARAZONO ◽  
Akira MIYATA ◽  
Rommel C. ZULUETA ◽  
Walter C. OECHEL
Keyword(s):  
Seasonal Variation ◽  
Growing Season ◽  
Co2 Fluxes ◽  
Tundra Ecosystem

Analytical Electron Microscopy of Ion-Implanted Metals

1985 ◽  
Vol 43 ◽  
pp. 282-285
Author(s):  
D.I. Potter ◽  
M. Ahmed ◽  
K. Ruffing
Keyword(s):  
Electron Microscopy ◽  
Ion Implantation ◽  
Friction And Wear ◽  
Analytical Electron Microscopy ◽  
Chemical Compositions ◽  
Surface Chemical ◽  
Near Surface ◽  
The Past ◽  
Analytical Electron ◽  
Property Changes

Ion implantation, used extensively for the past decade in fabricating semiconductor devices, now provides a unique means for altering the near-surface chemical compositions and microstructures of metals. These alterations often significantly improve physical properties that depend on the surface of the material; for example, catalysis, corrosion, oxidation, hardness, friction and wear. Frequently the mechanisms causing these beneficial alterations and property changes remain obscure and much of the current research in the area of ion implantation metallurgy is aimed at identifying such mechanisms. Investigators thus confront two immediate questions: To what extent is the chemical composition changed by implantation? What is the resulting microstructure? These two questions can be investigated very fruitfully with analytical electron microscopy (AEM), as described below.

scholarly journals CO<sub>2</sub> flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

2007 ◽  
Vol 4 (6) ◽  
pp. 1005-1025 ◽  
Author(s):  
L. Kutzbach ◽  
J. Schneider ◽  
T. Sachs ◽  
M. Giebels ◽  
H. Nykänen ◽  
...  
Keyword(s):  
Linear Regression ◽  
Nonlinear Regression ◽  
Co2 Flux ◽  
Exponential Model ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Closed Chamber ◽  
Exponential Regression ◽  
Closure Time ◽  
Over Time

Abstract. Closed (non-steady state) chambers are widely used for quantifying carbon dioxide (CO2) fluxes between soils or low-stature canopies and the atmosphere. It is well recognised that covering a soil or vegetation by a closed chamber inherently disturbs the natural CO2 fluxes by altering the concentration gradients between the soil, the vegetation and the overlying air. Thus, the driving factors of CO2 fluxes are not constant during the closed chamber experiment, and no linear increase or decrease of CO2 concentration over time within the chamber headspace can be expected. Nevertheless, linear regression has been applied for calculating CO2 fluxes in many recent, partly influential, studies. This approach has been justified by keeping the closure time short and assuming the concentration change over time to be in the linear range. Here, we test if the application of linear regression is really appropriate for estimating CO2 fluxes using closed chambers over short closure times and if the application of nonlinear regression is necessary. We developed a nonlinear exponential regression model from diffusion and photosynthesis theory. This exponential model was tested with four different datasets of CO2 flux measurements (total number: 1764) conducted at three peatlands sites in Finland and a tundra site in Siberia. Thorough analyses of residuals demonstrated that linear regression was frequently not appropriate for the determination of CO2 fluxes by closed-chamber methods, even if closure times were kept short. The developed exponential model was well suited for nonlinear regression of the concentration over time c(t) evolution in the chamber headspace and estimation of the initial CO2 fluxes at closure time for the majority of experiments. However, a rather large percentage of the exponential regression functions showed curvatures not consistent with the theoretical model which is considered to be caused by violations of the underlying model assumptions. Especially the effects of turbulence and pressure disturbances by the chamber deployment are suspected to have caused unexplainable curvatures. CO2 flux estimates by linear regression can be as low as 40% of the flux estimates of exponential regression for closure times of only two minutes. The degree of underestimation increased with increasing CO2 flux strength and was dependent on soil and vegetation conditions which can disturb not only the quantitative but also the qualitative evaluation of CO2 flux dynamics. The underestimation effect by linear regression was observed to be different for CO2 uptake and release situations which can lead to stronger bias in the daily, seasonal and annual CO2 balances than in the individual fluxes. To avoid serious bias of CO2 flux estimates based on closed chamber experiments, we suggest further tests using published datasets and recommend the use of nonlinear regression models for future closed chamber studies.

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