Leaf conductance decreased under free-air CO2 enrichment (FACE) for three perennials in the Nevada desert

A common response of plants to elevated atmospheric CO₂ concentration (CO₂) is decreased leaf conductance. Consequently, leaf temperature is predicted to increase under elevated CO₂.

Diurnal patterns of leaf conductance and temperature were measured for three desert perennials, the C₃ shrub Larrea tridentata, C₃ tussock grass Achnatherum hymenoides and C₄ tussock grass Pleuraphis rigida, at the Nevada Desert FACE facility. Measurements were made on ambient and c. 550 µmol mol⁻¹ CO₂ plots through both a wet and dry year.

Reductions in conductance were 35%, 20% and 13% for Pleuraphis, Achnatherum and Larrea, respectively. Decreased conductance occurred throughout the day only for Pleuraphis. Both C₃ species had smaller CO₂ effects during dry periods than wet. Leaf temperature did not differ significantly between elevated and ambient CO₂ for any species. Comparisons of blower-control and nonring plots indicated that the FACE apparatus did not confound our results.

All three species exhibited decreased leaf conductance under elevated CO₂, although reductions were not uniform during the day or among years. Nonetheless, leaf energy balance was only minimally changed for these microphyllous desert perennials.