scholarly journals Global trends in air-water CO2 exchange over seagrass meadows revealed by atmospheric Eddy Covariance

2020 ◽  
Author(s):  
Bryce R Van Dam ◽  
Pierre Polsenaere ◽  
Aylin Barreras-Apodaca ◽  
Christian Lopes ◽  
Zulia Mayari Sanchez-Mejia ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Co2 Exchange ◽  
Global Trends ◽  
Seagrass Meadows

scholarly journals Global Trends in Air‐Water CO 2 Exchange Over Seagrass Meadows Revealed by Atmospheric Eddy Covariance

2021 ◽  
Vol 35 (4) ◽  
Author(s):  
Bryce Van Dam ◽  
Pierre Polsenaere ◽  
Aylin Barreras‐Apodaca ◽  
Christian Lopes ◽  
Zulia Sanchez‐Mejia ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Global Trends ◽  
Seagrass Meadows

scholarly journals Global trends in air-water CO2 exchange over seagrass meadows revealed by atmospheric Eddy Covariance

2021 ◽  
Author(s):  
Bryce Van Dam ◽  
Pierre Polsenaere ◽  
Aylin Barreras-Apodaca ◽  
Christian Lopes ◽  
Zulia Sanchez-Mejia ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Global Scale ◽  
Co2 Exchange ◽  
Wavelet Coherence ◽  
Gas Transfer ◽  
Physical Factors ◽  
Surface Drag ◽  
Seagrass Meadows ◽  
Greenhouse Gas Inventories ◽  
Wavelet Coherence Analysis

<p><span>Coastal vegetated habitats like seagrass meadows can mitigate anthropogenic carbon emissions by sequestering CO<sub>2</sub> as “blue carbon” (BC). Already, some coastal ecosystems are actively managed to enhance BC storage, with associated BC stocks included in national greenhouse gas inventories. However, the extent to which BC burial fluxes are enhanced or counteracted by other carbon fluxes, especially air-water CO<sub>2</sub> flux (FCO<sub>2</sub>) remains poorly understood. To this end, we synthesized all available direct FCO<sub>2</sub> measurements over seagrass meadows made using a common method (atmospheric Eddy Covariance), across a globally-representative range of ecotypes. Of the four sites with seasonal data coverage, two were net CO<sub>2</sub> sources, with average FCO<sub>2</sub> equivalent to 44 - 115% of the global average BC burial rate. At the remaining sites, net CO<sub>2</sub> uptake was 101 - 888% of average BC burial. A wavelet coherence analysis demonstrates that FCO<sub>2</sub> was most strongly related to physical factors like temperature, wind, and tides. In particular, tidal forcing appears to shape global-scale patterns in FCO<sub>2</sub>, likely due to a complex suite of drivers including: lateral carbon exchange, bottom-driven turbulence, and pore-water pumping. Lastly, sea-surface drag coefficients were always greater than prediction for the open ocean, supporting a universal enhancement of gas-transfer in shallow coastal waters. Our study points to the need for a more comprehensive approach to BC assessments, considering not only organic carbon storage, but also air-water CO<sub>2 </sub>exchange, and its complex biogeochemical and physical drivers.</span></p>

scholarly journals Responses of Forest Carbon Cycle to Drought and Elevated CO2

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 212
Author(s):  
Jun-Lan Xiao ◽  
Feng Zeng ◽  
Qiu-Lan He ◽  
Yu-Xia Yao ◽  
Xiao Han ◽  
...  
Keyword(s):  
Water Stress ◽  
Elevated Co2 ◽  
Carbon Sink ◽  
Ecosystem Respiration ◽  
Co2 Exchange ◽  
Positive Influence ◽  
Research Field ◽  
Co2 Fertilization ◽  
Global Trends ◽  
Elevated Atmospheric Co2

Forests play a pivotal role in mitigating global warming as an important carbon sink. Recent global greening trends reflect a positive influence of elevated atmospheric CO2 on terrestrial carbon uptake. However, increasingly frequent and intense drought events endanger the carbon sequestration function of forests. This review integrates previous studies across scales to identify potential global trends in forest responses to drought and elevated CO2 as well as to identify data needs in this important research field. The inconsistent responses of ecosystem respiration to drought contributes to the change of forest net CO2 exchange, which depends on the balance of opposite effects of warming and water stress on respiration. Whether CO2 fertilization can offset the effects of drought remains controversial, however, we found a potential overestimation of global CO2 fertilization effects because of increasing water stress and other limitations such as light and nutrients (N, P) as well as the possibility of photosynthetic acclimation.

scholarly journals An airborne regional carbon balance for Central Amazonia

2007 ◽  
Vol 4 (1) ◽  
pp. 99-123 ◽  
Author(s):  
J. Lloyd ◽  
O. Kolle ◽  
H. Fritsch ◽  
S. R. de Freitas ◽  
M. A. F. Silva Dias ◽  
...  
Keyword(s):  
Exchange Rates ◽  
Eddy Covariance ◽  
Carbon Balance ◽  
Carbon Budget ◽  
Carbon Sink ◽  
Co2 Exchange ◽  
Night Time ◽  
Central Amazonia ◽  
Regional Estimates ◽  
Good Agreement

Abstract. We obtained regional estimates of surface CO2 exchange rates using atmospheric boundary layer budgeting techniques above tropical forest near Manaus, Brazil. Comparisons were made with simultaneous measurements from two eddy covariance towers below. Although there was good agreement for daytime measurements, large differences emerged for integrating periods dominated by the night-time fluxes. These results suggest that a systematic underestimation of night time respiratory effluxes may be responsible for the high Amazonian carbon sink suggested by several previous eddy covariance studies. Large CO2 fluxes from riverine sources or high respiratory losses from recently disturbed forests do not need to be invoked in order to balance the carbon budget of the Amazon. Our results do not, however, discount some contribution of these processes to the overall Amazon carbon budget.

scholarly journals Radiocarbon isotopic evidence for assimilation of atmospheric CO<sub>2</sub> by the seagrass <i>Zostera marina</i>

2015 ◽  
Vol 12 (20) ◽  
pp. 6251-6258 ◽  
Author(s):  
K. Watanabe ◽  
T. Kuwae
Keyword(s):  
Carbon Source ◽  
Zostera Marina ◽  
Inorganic Carbon ◽  
Aquatic Vegetation ◽  
Dissolved Inorganic Carbon ◽  
Isotope Analysis ◽  
Co2 Exchange ◽  
Atmospheric Co2 ◽  
Isotopic Signatures ◽  
Seagrass Meadows

Abstract. Submerged aquatic vegetation takes up water-column dissolved inorganic carbon (DIC) as a carbon source across its thin cuticle layer. It is expected that marine macrophytes also use atmospheric CO2 when exposed to air during low tide, although assimilation of atmospheric CO2 has never been quantitatively evaluated. Using the radiocarbon isotopic signatures (Δ14C) of the seagrass Zostera marina, DIC and particulate organic carbon (POC), we show quantitatively that Z. marina takes up and assimilates atmospheric modern CO2 in a shallow coastal ecosystem. The Δ14C values of the seagrass (−40 to −10 ‰) were significantly higher than those of aquatic DIC (−46 to −18 ‰), indicating that the seagrass uses a 14C-rich carbon source (atmospheric CO2, +17 ‰). A carbon-source mixing model indicated that the seagrass assimilated 0–40 % (mean, 17 %) of its inorganic carbon as atmospheric CO2. CO2 exchange between the air and the seagrass might be enhanced by the presence of a very thin film of water over the air-exposed leaves during low tide. Our radiocarbon isotope analysis, showing assimilation of atmospheric modern CO2 as an inorganic carbon source, improves our understanding of the role of seagrass meadows in coastal carbon dynamics.

Cross validation of open-top chamber and eddy covariance measurements of ecosystem CO2 exchange in a Florida scrub-oak ecosystem

2002 ◽  
Vol 9 (1) ◽  
pp. 84-95 ◽  
Author(s):  
Sabina Dore ◽  
Graham J. Hymus ◽  
David P. Johnson ◽  
C. R. Hinkle ◽  
Riccardo Valentini ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Cross Validation ◽  
Co2 Exchange ◽  
Open Top Chamber ◽  
Florida Scrub ◽  
Scrub Oak ◽  
Eddy Covariance Measurements ◽  
Oak Ecosystem

scholarly journals Spatial variability of CO<sub>2</sub> uptake in polygonal tundra: assessing low-frequency disturbances in eddy covariance flux estimates

2017 ◽  
Vol 14 (12) ◽  
pp. 3157-3169 ◽  
Author(s):  
Norbert Pirk ◽  
Jakob Sievers ◽  
Jordan Mertes ◽  
Frans-Jan W. Parmentier ◽  
Mikhail Mastepanov ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Eddy Covariance ◽  
Low Frequency ◽  
Optimization Method ◽  
Co2 Exchange ◽  
Aerial Photographs ◽  
Strong Increase ◽  
Vulnerability To Climate Change ◽  
Flux Measurements ◽  
Ice Wedge

Abstract. The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV) that mapped ice-wedge morphology to complement eddy covariance (EC) flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency) flux contributions were especially pronounced during snowmelt and introduced a large bias of −46 gC m−2 to the annual CO2 budget in conventional methods (the minus sign indicates a higher uptake by the ecosystem). Our improved flux calculations with the ogive optimization method indicated that the site was a strong sink for CO2 in 2015 (−82 gC m−2). Due to differences in light-use efficiency, wetter areas with low-centered polygons sequestered 47 % more CO2 than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2 K in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last 7 decades. Apparently, warming has thus far not been sufficient to initiate strong ice-wedge degradation, possibly due to the absence of extreme heat episodes in the maritime climate on Svalbard. However, in Arctic regions where ice-wedge degradation has already initiated the associated drying of landscapes, our results suggest a weakening of the CO2 sink in polygonal tundra.

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