Chamber Technology

Challenges of Making Flux Measurements

Soil CO₂ production is heavily influenced by environmental factors (soil temperature, soil moisture, organic content, etc.) and biological factors (above ground canopy size, growth activity, etc.). Soil CO₂ efflux is a physical process driven primarily by the CO₂ concentration diffusion gradient between the upper soil layers and the atmosphere near the soil surface. The fundamental challenge for making accurate soil CO₂ flux measurements is that the deployment of chambers must cause minimal disturbance to environmental conditions that have an impact on CO₂ production and transport inside the soil profile.

Chambers Designed to Minimize Environmental Perturbations

LI-8100A chambers are designed to minimize perturbations to the surrounding environmental conditions and measurement artifacts that can affect the natural soil CO₂ production and diffusion processes.

• Both survey and long-term chambers close automatically, eliminating variations caused by manual chamber placement.
• New patented pressure vent design minimizes pressure pulses at chamber closing, and allows chamber pressure to track the ambient pressure under calm and windy conditions.
• CO₂ flux rate is calculated at the CO₂ concentration of the surrounding ambient air. This minimizes effects resulting from the necessary increase in chamber CO₂ concentration during a measurement.

• A bowl-shaped chamber provides good mixing without using fans, thus eliminating potential for chamber pressure perturbation.
• Temperature artifacts are minimized by careful consideration of materials and coatings.
• The perforated baseplates of the Long-Term Chambers minimize perturbations to the soil environment around the chamber, including the prevention of a concentration gradient-induced impedance of soil CO₂ flux.