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Pore‐space CO 2 dynamics in a deep, well‐aerated soil
Author(s) -
Maier M.,
SchackKirchner H.,
Hildebrand E. E.,
Holst J.
Publication year - 2010
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.2010.01287.x
Subject(s) - carbon dioxide , saturation (graph theory) , soil science , soil horizon , vadose zone , characterisation of pore space in soil , soil water , environmental science , soil gas , chemistry , soil respiration , water table , atmosphere (unit) , infiltration (hvac) , atmospheric sciences , environmental chemistry , groundwater , porosity , geology , materials science , physics , mathematics , geotechnical engineering , organic chemistry , combinatorics , thermodynamics , composite material
Most studies implicitly consider soil carbon dioxide (CO 2 ) efflux as the instantaneous soil respiration and thereby neglect possible changes in the amount of CO 2 stored in the soil pore‐space. We measured the CO 2 concentration profile of a well‐aerated soil continuously to evaluate the dynamics of the stored CO 2 and to analyse the influence of environmental factors. For 25% of the observation period, changes in the amount of stored CO 2 accounted for more than 15% of the soil‐CO 2 efflux. The following factors were identified to interfere with steady‐state CO 2 storage: (i) the fluctuating groundwater table altered the volume of the vadose zone, causing viscous airflow in air‐filled soil pores, (ii) atmospheric turbulence caused pressure‐pumping at the soil–atmosphere interface and (iii) intense rain greatly reduced the diffusivity of the uppermost soil layer. The friction velocity above the canopy was strongly correlated with fluctuations in the differential pressure between soil air and atmosphere, but no static pressure gradient could be detected because of the permeable nature of the soil. Unexpected short‐term declines in the soil CO 2 concentration were observed during intense rainfall events. These declines were explained by the intensified CO 2 saturation deficit of the infiltrating rainwater caused by the carbonate chemistry of the soil solution.