RELATIVE CARBON FLUXES FROM SOIL, DEEP VADOSE ZONE AND GROUNDWATER TO ATMOSPHERE AND RIVER OF A SEMI-ARID FLOODPLAIN IN COLORADO

Abstract. The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated. Carbon dioxide partial pressure in the soil gas (pCO2), alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley) mesocosms. The dissolved inorganic carbon (DIC) percolation flux was calculated from the pCO2, alkalinity and the water flux at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn) emanation rates and soil air Rn concentration profiles, and was used in conjunction with measured pCO2 gradients to calculate the soil CO2 production. Carbon dioxide fluxes were modelled using the HP1 module of the Hydrus 1-D software. The average CO2 effluxes to the atmosphere from unplanted and planted mesocosm ecosystems during 78 days of experiment were 0.1 ± 0.07 and 4.9 ± 0.07 μmol carbon (C) m−2 s−1, respectively, and largely exceeded the corresponding DIC percolation fluxes of 0.01 ± 0.004 and 0.06 ± 0.03 μmol C m−2 s−1. Post-harvest soil respiration (Rs) was only 10% of the Rs during plant growth, while the post-harvest DIC percolation flux was more than one third of the flux during growth. The Rs was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO2 and the drainage flux due to low solution pH. Plant biomass and soil pCO2 were high in the mesocosms as compared to a standard field situation. Our results indicate no change of the cropland C balance under elevated atmospheric CO2 in a warmer future climate, in which plant biomass and soil pCO2 are expected to increase.

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SOIL MOISTURE CONTROLS ON WATER VAPOR AND CARBON FLUXES IN SEMI-ARID REGIONS

Dryland Ecohydrology ◽

10.1007/1-4020-4260-4_5 ◽

2006 ◽

pp. 67-83 ◽

Cited By ~ 1

Author(s):

John D. ALBERTSON ◽

Christopher A. WILLIAMS ◽

Todd M. SCANLON ◽

Nicola MONTALDO

Keyword(s):

Soil Moisture ◽

Water Vapor ◽

Arid Regions ◽

Carbon Fluxes ◽

Semi Arid

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Unsaturated CBR design approach of flexible pavement

10.5592/co/cetra.2020.1005 ◽

2021 ◽

Author(s):

Frank Ikechukwu Aneke ◽

Mohamed Mostafa Hassan

Keyword(s):

Volume Change ◽

Vadose Zone ◽

Arid Regions ◽

Design Method ◽

Flexible Pavement ◽

Design Approach ◽

Test Results ◽

Subgrade Soils ◽

Design Values ◽

Semi Arid

Subgrades in arid and semi-arid regions are often subjected to seasonal moisture variations that trigger volume change. To account for moisture changes in a vadose zone during pavement design, matric suction (ψ_m) is unavoidably required. In that context, ψ_m inclusion in CBR design becomes imperative. This study presents two CBR design approaches of flexible pavement, i.e. the conventional CBR design, and unsaturated CBR design methods. To compare these design approaches, subgrade soils were selected and a series of suction tests, CBR, and unsaturated CBR tests were performed to obtain the CBR design values of the subgrade materials. The results illustrate a linear relationship between suction and CBR values of the subgrades. The test results, further revealed that the unsaturated CBR design values are 2 to 2.5 times greater than the conventional CBR values. Based on the experimental results, the design analysis confirmed that the unsaturated CBR design approach is more conservative and rational compare to the conventional CBR design method.

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Comments for "Seasonal effects of irrigation on land-atmosphere latent heat, sensible heat and carbon fluxes in semi-arid basin" by Zeng et al.

10.5194/esd-2016-45-rc2 ◽

2016 ◽

Author(s):

Anonymous

Keyword(s):

Latent Heat ◽

Carbon Fluxes ◽

Seasonal Effects ◽

Sensible Heat ◽

Semi Arid

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Variations in seasonal and inter-annual carbon fluxes in a semi-arid sandy maize cropland ecosystem in China’s Horqin Sandy Land

Environmental Science and Pollution Research ◽

10.1007/s11356-021-15751-z ◽

2021 ◽

Author(s):

Yayi Niu ◽

Yuqiang Li ◽

Mingming Wang ◽

Xuyang Wang ◽

Yun Chen ◽

...

Keyword(s):

Carbon Fluxes ◽

Horqin Sandy Land ◽

Sandy Land ◽

Annual Carbon ◽

Semi Arid ◽

Cropland Ecosystem

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A wildfire event influences ecosystem carbon fluxes but not soil respiration in a semi-arid woodland

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2016.05.019 ◽

2016 ◽

Vol 226-227 ◽

pp. 57-66 ◽

Cited By ~ 7

Author(s):

Qiaoqi Sun ◽

Wayne S. Meyer ◽

Georgia R. Koerber ◽

Petra Marschner

Keyword(s):

Soil Respiration ◽

Carbon Fluxes ◽

Ecosystem Carbon ◽

Ecosystem Carbon Fluxes ◽

Semi Arid

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Drought and heatwave impacts on semi-arid ecosystems' carbon fluxes along a precipitation gradient

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2019.0519 ◽

2020 ◽

Vol 375 (1810) ◽

pp. 20190519 ◽

Cited By ~ 1

Author(s):

Tarek S. El-Madany ◽

Arnaud Carrara ◽

M. Pilar Martín ◽

Gerardo Moreno ◽

Olaf Kolle ◽

...

Keyword(s):

Carbon Cycle ◽

Ecosystem Respiration ◽

Carbon Fluxes ◽

Arid Ecosystems ◽

Severe Drought ◽

Precipitation Gradient ◽

Continental Scale ◽

Compound Event ◽

The Impact ◽

Semi Arid

The inter-annual variability (IAV) of the terrestrial carbon cycle is tightly linked to the variability of semi-arid ecosystems. Thus, it is of utmost importance to understand what the main meteorological drivers for the IAV of such ecosystems are, and how they respond to extreme events such as droughts and heatwaves. To shed light onto these questions, we analyse the IAV of carbon fluxes, its relation with meteorological variables, and the impact of compound drought and heatwave on the carbon cycle of two similar ecosystems, along a precipitation gradient. A four-year long dataset from 2016 to 2019 was used for the FLUXNET sites ES-LMa and ES-Abr, located in central (39°56'25″ N 5°46'28″ W) and southeastern (38°42'6″ N 6°47'9″ W) Spain. We analyse the physiological impact of compound drought and heatwave on the dominant tree species, Quercus ilex. Our results show that the gross primary productivity of the wetter ecosystem was less sensitive to changes in soil water content, compared to the dryer site. Still, the wetter ecosystem was a source of CO 2 each year, owing to large ecosystem respiration during summer; while the dry site turned into a CO 2 sink during wet years. Overall, the impact of the summertime compound event on annual CO 2 fluxes was marginal at both sites, compared to drought events during spring or autumn. This highlights that drought timing is crucial to determine the annual carbon fluxes in these semi-arid ecosystems. This article is part of the theme issue ‘Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale’.

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