CO₂ -responsiveness of leaf isoprene emission: Why do species differ?

Area of Science:

• Plant physiology and global change biology.
• Biogeochemical cycles and ecosystem responses.

Background:

• Leaf isoprene emission (I) declines with elevated atmospheric CO2, impacting global climate.
• Significant, yet poorly understood, interspecific variation exists in this CO2-responsiveness.

Purpose of the Study:

• To investigate the reasons behind interspecific variability in isoprene emission response to elevated CO2.
• To test the hypothesis that emission reduction magnitude correlates with precursor pool size and variability.

Main Methods:

• Studied changes in isoprene emission (I) and intermediate pool sizes (DMADP, MEcDP) in nine woody species.
• Increased atmospheric CO2 concentration from 400 to 1500 μmol/mol.

Main Results:

• Isoprene emission (I) decreased by an average of 65% at higher CO2, with species-specific responses varying by an order of magnitude.
• Elevated CO2 reduced both substrate pools (DMADP and MEcDP).
• Interspecific variation in CO2-responsiveness correlated with substrate pool reduction, total pool size, and DMADP's share of the total pool.

Conclusions:

• Highlights substantial interspecific variation in the response of isoprene emission to elevated CO2.
• Links this variation to species-specific changes in substrate availability and intermediate pool dynamics.