At the ecosystem scale, gas emissions vary widely in both time and space—even at very fine spatial scales (on the order of square meters). This variability complicates the modeling of gas fluxes and results in large uncertainties in annual flux estimates. To reduce these uncertainties, fine-scale spatial analysis (on a 0.5 m grid) of gas concentrations and fluxes would help better characterize their spatial distribution, enabling :

• Adaptation of existing measurement protocols for better flux representativeness ;

• Estimation of homogeneous emission areas for more accurate flux budgets.

Flux measurements in ecosystems are typically obtained using three main techniques that are complementary in terms of spatial resolution :

• Eddy covariance flux measurements (large scale : several hectares), providing high-frequency data (>10 Hz) by linking gas concentration at a point with wind speed and direction ;

• Incubation chambers, usually closed, placed over a portion of the ecosystem (<1 m²) to monitor changes in gas concentrations over time ;

• Soil gradient methods, used at even finer spatial scales.

Understanding the fine-scale drivers of gas emissions requires spatial analysis of fluxes in relation to key environmental variables (e.g., temperature, vegetation, and soil moisture). Eddy covariance systems lack the spatial resolution for this type of analysis, and soil gradient methods are too labor-intensive to provide spatially representative data. Thus, chamber-based techniques appear to be the most suitable for studying spatial variability in fluxes and its underlying causes.

Measurements can be conducted manually, although automated chambers—commercially available but still expensive—can also be used. A key advantage of the chamber method is the potential for deploying many replicates (depending on available resources), thereby improving representativeness.

The soil evapotranspiration chamber developed under the TERRA FORMA project builds upon instrumentation research conducted at CESBIO, which led to three prototype chambers capable of measuring multiple gases (CO₂, CH₄, O₂, N₂O, etc.). The objective is now to make these chambers connected (for easier data retrieval), to integrate the external gas analyzer, to correct measurements for wind conditions (a feature lacking in off-the-shelf systems), and to reduce the overall cost by a factor of 10 compared to commercial models. This cost reduction would enable more replicates and better spatial representativeness.

These chambers offer improved airtightness compared to traditional models, better air homogenization, lower disturbance to the system, and easier installation and maintenance.

Theme : Soil

Updated on 23 juin 2025