Measuring soil CO₂ flux

Increasing CO₂ concentrations in the atmosphere and the resulting consequences for the earth’s climate make understanding the sources and sinks of carbon and their exchange with the atmosphere a high research priority around the world. Soil CO₂ flux makes a significant contribution to the total carbon balance and is driven by complex environmental and biological processes that are variable in space and time.

The Li-Cor LI-8100 Automated Soil CO₂ Flux System allows users to make both short-term survey and long-term, unattended measurements of soil CO₂ flux. The measurement range is 0-3000 ppm (CO₂) and 0-80 mmol/mol (H₂O).

There are two optional short-term survey chambers: the 8100-102 (10 cm) and 8100-103 (20 cm). The 8100-102 chamber allows researchers to finetune chamber placements more easily. For example, in crop rows as more measurements can be performed with the 10 cm chamber over the available space within and between the rows, which is helpful when studying CO₂ flux across the root zones of various crops.

The 8100-103 chamber is exposed to a larger soil area, enabling better spatial averaging of CO₂ flux over heterogeneous soils; also, the 20 cm chamber uses the same soil collar as the long-term chambers. There are two, long-term chambers: the 8100-101 and 8100-104, for making unattended diurnal measurements and seasonal soil CO₂ flux patterns at a single location for weeks or months at a time. The 8100-101 is designed for use with the LI-8100 in a single-chamber, long-term system and can also be used for multiplexing with the LI-8150 multiplexer.

The 8100-104 is an economical, lightweight solution for multiplexer systems. It expands the capabilities of the LI-8100 system and provides an additional chamber option to measure both spatial and temporal variations of soil CO₂ flux.

Measuring CO₂ flux requires extensive sampling because of spatial heterogeneity of soils and temporal variations in the environmental processes that drive CO₂ flux. The LI-8100 Windows or Interface Software for Palm OS provides intuitive settings for configuring either single-chamber or multiplexed systems to make repeated, automated flux measurements.