Plant responses to decadal scale increments in atmospheric CO₂ concentration: comparing two stomatal conductance...

Area of Science:

• Plant Physiology
• Environmental Science
• Climate Change Biology

Background:

• Elevated atmospheric CO2 concentrations are a key feature of climate change.
• Typical studies assess CO2 effects at single time points, potentially missing dynamic responses.
• Stomatal conductance (g_s) is crucial for plant water and carbon exchange.

Purpose of the Study:

• To investigate non-linear stomatal conductance (g_s) responses in C3 plants to simulated decadal increases in CO2.
• To compare g_s measurement accuracy between infrared gas analyzer (IRGA) and leaf porometer methods.
• To understand how diurnal stomatal behavior changes under projected future CO2 levels.

Main Methods:

• Exposed *Populus tremula*, *Populus tremuloides*, and *Sambucus racemosa* to 350, 420, 490, and 560 ppm CO2 for 126 days.
• Simulated decadal CO2 increments based on the RCP4.5 scenario.
• Measured stomatal conductance (g_s) using both IRGA and leaf porometer.

Main Results:

• Species exhibited non-linear responses in g_s to increasing CO2 concentrations.
• Elevated CO2, even with small increments (70 ppm), shifted the timing of daily maximum g_s to later in the day for some species.
• Diurnal stomatal patterns were altered, deviating from typical mid-day depression under elevated CO2.

Conclusions:

• Plant responses to decadal CO2 increases are complex and non-linear.
• Altered diurnal stomatal behavior under future CO2 levels can significantly impact plant water use and carbon assimilation.
• These changes may have profound implications for soil-plant-atmosphere interactions and ecosystem processes.