Subterranean CO2 ventilation and its role in the net ecosystem carbon balance of a karstic shrubland

Sánchez‐Cañete, Enrique P.; Serrano-Ortiz, Penélope; Kowalski, Andrew S.; Oyonarte, Cecilio; Domingo, Francisco

doi:10.1029/2011gl047077

Cited by 42 publications

(45 citation statements)

References 37 publications

(28 reference statements)

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“…Deep-soil χ c (0.5 and 1.5 m) shows two cycles per day, in rhythm with p, whereas shallow χ c has just one. Shallow χ c is more affected by friction velocity (Table 3) because it is in the upper part of the soil, and thus more easily ventilated decreasing χ c (Hirsch et al, 2004;Sanchez-Canete et al, 2011). Similarly, Rey et al (2012a) concluded that the wind was the main driver of the net ecosystem carbon balance at this experimental site.…”

Section: Growing Period Dry Period Depthmentioning

confidence: 98%

Deep CO2 soil inhalation / exhalation induced by synoptic pressure changes and atmospheric tides in a carbonated semiarid steppe

et al. 2013

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Abstract. Knowledge of all the mechanisms and processes involved in soil CO 2 emissions is essential to close the global carbon cycle. Apart from molecular diffusion, the main physical component of such CO 2 exchange is soil ventilation. Advective CO 2 transport, through soil or snow, has been correlated with the wind speed, friction velocity or pressure (p). Here we examine variations in subterranean CO 2 molar fractions (χ c ) over two years within a vertical profile (1.5 m) in a semiarid ecosystem, as influenced by short-timescale p changes.Analyses to determine the factors involved in the variations in subterranean χ c were differentiated between the growing period and the dry period. In both periods it was found that variations in deep χ c (0.5-1.5 m) were due predominantly to static p variations and not to wind or biological influences. Within a few hours, the deep χ c can vary by fourfold, showing a pattern with two cycles per day, due to p oscillations caused by atmospheric tides. By contrast, shallow χ c (0.15 m) generally has one cycle per day as influenced by biological factors like soil water content and temperature in both periods, while the wind was an important factor in shallow χ c variations only during the dry period. Evidence of emissions was registered in the atmospheric boundary layer by eddy covariance during synoptic pressure changes when subterranean CO 2 was released; days with rising barometric pressure -when air accumulated belowground, including soil-respired CO 2 -showed greater ecosystem uptake than days with falling pressure. Future assessments of the net ecosystem carbon balance should not rely exclusively on Fick's law to calculate soil CO 2 effluxes from profile data.

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Section: Growing Period Dry Period Depthmentioning

confidence: 98%

Deep CO2 soil inhalation / exhalation induced by synoptic pressure changes and atmospheric tides in a carbonated semiarid steppe

et al. 2013

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“…The open-system model of carbonate dissolution assumes continuous equilibration of soil water DIC with soil CO 2 , causing the incorporation of a 14 C-free carbon derived from dissolution of the carbonate bedrock into to soil DIC pool, including the soil CO 2 . Very large fluxes of non-biogenic CO 2 have been observed karst terrains (Sanchez-Cañete et al, 2011), suggesting that it is possible for carbonate dissolution and precipitation processes to have an appreciable affect on the carbon isotope ratios of soil CO 2 in karst terrains.…”

Section: Heshang Cave Soil Carbonmentioning

confidence: 99%

Radiocarbon evidence for decomposition of aged organic matter in the vadose zone as the main source of speleothem carbon

Noronha

Johnson

Southon

et al. 2015

Quaternary Science Reviews

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a b s t r a c tSeveral recent studies have used records of the radiocarbon ( 14 C) bomb peak in speleothems to inversely model the soil a 14 CO 2 and the age distribution of soil organic material (SOM) above caves, in part to investigate the potential of speleothems as sensitive records of past SOM dynamics. The results of these modeling studies have suggested that soil CO 2 at karst sites is derived primarily from the decomposition of SOM with turnover times on the order of decades to centuries. This result is in stark contrast with observations of soil a 14 CO 2 at non-karst sites, which indicate that soil CO 2 is derived primarily from root respiration and decomposition of SOM with much shorter turnover times. This discrepancy suggests that SOM in karst settings may have a very different age distribution than sites that have been studied previously and/or that soil CO 2 is not the main source of speleothem carbon. To help resolve this discrepancy, we present an improved inverse model which we use to estimate the age of CO 2 above several caves. We also present results from a detailed case study of soil carbon dynamics at Heshang Cave, China. This work demonstrates that SOM in karst sites may be much older than SOM in non-karst soils that have been studied previously, but that CO 2 produced in the shallow soil zone is unlikely to be the main source of speleothem carbon. A review of the literature suggests that the most likely explanation for the aforementioned discrepancy is that decomposition of down-washed SOM in the vadose zone is the dominant source of speleothem carbon.

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“…As several authors showed a strong correlation between the amount of atmospheric turbulence and ventilation measured at this site, we set up an equation using the friction velocity u * (see Fig. 1 inset, and also Kowalski et al, 2008;Sanchez-Cañete et al, 2011;Serrano-Ortiz et al, 2010). u * (m s −1 ) is related to surface shear stress, responsible for generating turbulence, and therefore a proxy for atmospheric turbulence.…”

Section: Model Descriptionmentioning

confidence: 99%

Atmospheric turbulence triggers pronounced diel pattern in karst carbonate geochemistry

et al. 2013

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Abstract. CO2 exchange between terrestrial ecosystems and the atmosphere is key to understanding the feedbacks between climate change and the land surface. In regions with carbonaceous parent material, CO2 exchange patterns occur that cannot be explained by biological processes, such as disproportionate outgassing during the daytime or nighttime CO2 uptake during periods when all vegetation is senescent. Neither of these phenomena can be attributed to carbonate weathering reactions, since their CO2 exchange rates are too small. Soil ventilation induced by high atmospheric turbulence is found to explain atypical CO2 exchange between carbonaceous systems and the atmosphere. However, by strongly altering subsurface CO2 concentrations, ventilation can be expected to influence carbonate weathering rates. By imposing ventilation-driven CO2 outgassing in a carbonate weathering model, we show here that carbonate geochemistry is accelerated and does play a surprisingly large role in the observed CO2 exchange pattern of a semi-arid ecosystem. We found that by rapidly depleting soil CO2 during the daytime, ventilation disturbs soil carbonate equilibria and therefore strongly magnifies daytime carbonate precipitation and associated CO2 production. At night, ventilation ceases and the depleted CO2 concentrations increase steadily. Dissolution of carbonate is now enhanced, which consumes CO2 and largely compensates for the enhanced daytime carbonate precipitation. This is why only a relatively small effect on global carbonate weathering rates is to be expected. On the short term, however, ventilation has a drastic effect on synoptic carbonate weathering rates, resulting in a pronounced diel pattern that exacerbates the non-biological behavior of soil–atmosphere CO2 exchanges in dry regions \\mbox{with carbonate soils}.

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Subterranean CO₂ ventilation and its role in the net ecosystem carbon balance of a karstic shrubland

Cited by 42 publications

References 37 publications

Deep CO<sub>2</sub> soil inhalation / exhalation induced by synoptic pressure changes and atmospheric tides in a carbonated semiarid steppe

Deep CO<sub>2</sub> soil inhalation / exhalation induced by synoptic pressure changes and atmospheric tides in a carbonated semiarid steppe

Radiocarbon evidence for decomposition of aged organic matter in the vadose zone as the main source of speleothem carbon

Atmospheric turbulence triggers pronounced diel pattern in karst carbonate geochemistry

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Subterranean CO2 ventilation and its role in the net ecosystem carbon balance of a karstic shrubland

Cited by 42 publications

References 37 publications

Deep CO&lt;sub&gt;2&lt;/sub&gt; soil inhalation / exhalation induced by synoptic pressure changes and atmospheric tides in a carbonated semiarid steppe

Deep CO&lt;sub&gt;2&lt;/sub&gt; soil inhalation / exhalation induced by synoptic pressure changes and atmospheric tides in a carbonated semiarid steppe

Radiocarbon evidence for decomposition of aged organic matter in the vadose zone as the main source of speleothem carbon

Atmospheric turbulence triggers pronounced diel pattern in karst carbonate geochemistry

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Subterranean CO₂ ventilation and its role in the net ecosystem carbon balance of a karstic shrubland

Deep CO<sub>2</sub> soil inhalation / exhalation induced by synoptic pressure changes and atmospheric tides in a carbonated semiarid steppe

Deep CO<sub>2</sub> soil inhalation / exhalation induced by synoptic pressure changes and atmospheric tides in a carbonated semiarid steppe