Measuring Gas Exchange in Arid Environments

Arid environments cover 33% of the Earth's surface and the environmental parameters of these biomes has caused the plants that inhabit them to have unique mechanisms and lifecycle patterns. The most obvious of these adaptations for temperate arid lands is CAM photosynthesis, a biochemical adaptation to high heat, high quantum flux, and low water availability. CAM is an extension of C₃ photosynthesis that temporally fixes CO₂ allowing the plant's stomatal cycles to be reversed. Stomates open during the night to allow CO₂ fixation without excessive H₂O loss, storing the CO₂ as crassulacean acid until light is available. During the day, the acid is converted back to CO₂ and combined with the energetic matabolites from the light reactions to complete the photosynthetic carbon reaction chain.

Another consideration is the lifestyle adaptation of these plants. They tend to grow either very slowly or very quickly, which must be considered when choosing a photosynthesis measurement regime or field campaign. Plant phenology must also be considered, as arid environment plants tend to have adaptations to conserve what little water they can acquire including small leaves or waxy cuticles.

Soil flux can also be measured to explore the microbial activity and root respiration, especially the activity of biological soil crusts.

LI-COR Instruments for Arid Photosynthesis

The LI-6400XT Portable Photosynthesis System

• Compact, rugged, field portable instrument
• Accurate and precise
• Measures fluorescence and gas exhange simultaneously

LI-8100A Automated
Soil CO₂ Flux System

• Measures CO₂ exchange from soils
• Multiplexed configuration available for larger sampling area
• Useful for survey or long-term measurements

6400-09 Soil CO₂
flux chamber

For owners of the LI-6400XT Portable Photosynthesis System, the 6400-09 Soil CO₂ flux chamber enables the LI-6400XT to measure soil CO₂ flux.