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 thre e desert perennials, the C-3 shrub Larrea tridentata, C-3 tussock grass Ach natherum hymenoides and C-4 tussock grass Pleuraphis rigida, at the Nevada Desert FACE facility. Measurements were made on ambient and c. 550 mu mol m ol(-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 through out the da y only for Pleuraphis. Both C-3 species had smaller CO2 effects during dry periods than wet. Leaf temperature did not differ significantly between ele vated and ambient CO2 for any species. Comparisons of blower-control and no nring 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. Nonethe less, leaf energy balance was only minimally changed for these microphyllou s desert perennials.