Open AccessMultistep Outflow Experiments to Determine Soil Physical and Carbon Dioxide Production Parameters
Author(s) -
Weihermüller L.,
Huisman J. A.,
Graf A.,
Herbst M.,
Sequaris J.-M.
Publication year - 2009
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2008.0041
Subject(s) - soil water , outflow , carbon dioxide , environmental science , soil science , water potential , chemistry , characterisation of pore space in soil , porosity , physics , organic chemistry , meteorology
Soil water content (SWC) plays a crucial role in the production and transport of CO 2 in soils. Classical approaches estimating the effects of SWC on soil respiration are incubation experiments, where soil structure is disturbed and transport processes are neglected. Nevertheless, such data govern the water reduction function of C turnover models. In our approach, the water reduction control parameters (WRCP) of a water reduction function were estimated from column experiments using inverse modeling. Therefore, we used the SOILCO2–RothC model in combination with multistep outflow (MSO) experiments. First, the effective hydraulic properties were estimated and then used in a second experiment to estimate the WRCP and rate constants of the resistant plant material (RPM) C pool. The results showed that the estimated hydraulic parameters can be used for the prediction of CO 2 production and transport of a second MSO experiment only if the WRCP and the C turnover rate of the RPM pool of RothC will also be optimized. Optimizing only the WRCP matched the CO 2 efflux fairly well but the WRCP at the highest matric potential, which determines the start of reduction, was too low at −1.61 cm and (water‐filled pore space [WFPS] = 99.9%). Calibrating both WRCP and the RPM rate constant matched the efflux again fairly well and the results indicate a reduction of optimal CO 2 production at water contents of 0.224 m 3 m −3 or 53.3% WFPS. Also, the estimated RPM rate constant seems to be in a reasonable range at k RPM = 2.5791 × 10 −7 cm −1 .