Soil respiration partitioning and its components in the total agro-ecosystem respiration

Poster (2013, April 09)

Modelling total soil respiration in agricultural soils.

Poster (2010, January 12)

Soil respiration is a process which results in CO2 release from the soil to the atmosphere. It comprises two main components. The first one is heterotrophic respiration: CO2 is produced by soil ... [more ▼]

Soil respiration is a process which results in CO2 release from the soil to the atmosphere. It comprises two main components. The first one is heterotrophic respiration: CO2 is produced by soil microorganisms while decomposing the substrate. The second one is autotrophic respiration in which CO2 originates from roots and rhizospheric organisms. All the CO2 is then transported to the surface by diffusion (see Goffin et al., this session). Many biotic and abiotic factors play a role in soil respiration, making this process complex to analyze and understand. Temperature often appears as the most important driving variable. Besides that, interest in the future CO2 emissions from agricultural soils has been growing. Indeed, these ecosystems are a major concern from environmental, economic and social points of view. In particular, the choice of cultural practices and residue management techniques has a strong influence on CO2 emissions from agricultural systems. This work aims at getting to a better understanding of soil respiration in agricultural soils. To reach this goal, many semi-mechanistic models have been previously developed at very different spatio-temporal scales. We intend to adapt such an existing model to crop soils, within a spatial scale of a cultivated field and an annual temporal scale. The model will be validated by using flux measurements carried out at three different crop sites situated in the Hesbaye region in Belgium (Lonzée) and in the South West of France (Lamasquère, Auradé). The study was focused first on soil heterotrophic respiration. Within this part, short term sensitivity of this component to temperature was studied by means of a laboratory incubation experiment. This one was performed with soil samples taken at the Lonzée site. Among the many interesting results we got, it showed a clear sensitivity of soil heterotrophic respiration to short term temperature changes. In parallel, the soil heterotrophic model was calibrated on soil chamber measurements taken at the Lonzée site (Belgium). Next steps in this part of the work will be to calibrate the model using the data from the French sites, and finally to validate the model on the three sites. Afterwards, an autotrophic respiration submodel will be implemented and the results compared to field measurements carried out at the three sites. A further development could consist in simulating agricultural practices to take their impacts on CO2 emissions from crops into account. [less ▲]

Modelling soil heterotrophic respiration in an agricultural soil: Model structure and first comparison with experimental data.

Poster (2008, November 17)

Ce travail visait à adapter un modèle de respiration hétérotrophe du sol à un site agricole situé en Hesbaye (Belgique) et cultivé avec une rotation betterave sucrière / blé d’hiver / pomme de terre / blé ... [more ▼]

Ce travail visait à adapter un modèle de respiration hétérotrophe du sol à un site agricole situé en Hesbaye (Belgique) et cultivé avec une rotation betterave sucrière / blé d’hiver / pomme de terre / blé d’hiver. A long terme, ce modèle fera partie intégrante d’un modèle plus important qui décrira la respiration totale du sol et l’évolution du contenu en carbone du sol dans les cultures. Le modèle utilisé dans ce travail est dérivé du modèle Century, possède un pas de temps journalier et couvre une échelle spatiale de l’ordre de l’écosystème. La paramétrisation du modèle a été réalisée sur base d’une recherche bibliographique et de données collectées sur le site Carbo-Europe de Lonzée. Les caractéristiques du sol sont issues d’analyses réalisées sur des sols limoneux, typiques de la région de Hesbaye. Les variables conductrices (variables météorologiques et apports de litière) furent obtenues suite à une campagne de mesures de 4 ans réalisée sur le site expérimental de Lonzée. Les paramètres biochimiques du blé, de la pomme de terre et de la betterave furent tirés de la littérature. Une analyse de sensibilité fut réalisée en vue de classer les différents paramètres par rapport à leur impact sur le taux de respiration et les contenus en carbone de chaque pool. Les paramètres les plus importants étaient ceux contrôlant la réponse à la température, l’apport de litière et les teneurs en lignine et en azote. Des différences d’impact à court et long terme ont aussi été mises en évidence, notamment à cause de la dynamique de stabilisation des pools et des types de résidus de culture. Finalement, cette analyse nous a permis de définir de futures expériences qui seraient nécessaires pour améliorer l’ajustement du modèle sur des données expérimentales. [less ▲]

Cross-calibration functions for soil CO2 efflux measurement systems

in Annals of Forest Science : a Multidisciplinary and International Journal (2006), 63(5), 477-484

Different soil CO2 efflux measurement systems and methodologies were used to estimate the annual soil respiration of different forest sites. To allow comparison between these annual values, this study ... [more ▼]

Different soil CO2 efflux measurement systems and methodologies were used to estimate the annual soil respiration of different forest sites. To allow comparison between these annual values, this study aimed to cross-calibrate five soil CO2 efflux (RS) closed dynamic chamber systems, and compare the in situ measurement methodologies. We first assessed the impact of the measurement methodology on RS by studying the effects of three parameters: record duration, time lag before starting to record and the mode of chamber-soil contact (use of collars or insertion of the chambers into the soil). Secondly, we directly compared systems with identical methodology during field measurements on three forest sites. We observed a significant influence of the chamber-soil contact mode (no impact of the record duration and duration before starting to record). Measurements obtained by insertion led to significantly higher estimates of RS than those obtained using collars (up to 28%). Our inter-comparison showed that deviations existing between in situ measurements performed with the different systems were partly systematic and could be corrected using simple linear equations. Measurements of pressure difference between the inside and the outside of soil chambers allowed explaining a part of the observed deviations between systems. Finally, we assessed the influence of the cross-calibration equations on annual respiration of two beech forest soils. [less ▲]