Spring Leaf Flush in Aspen Trees
McGrath, J.M., Karnosky, D.F. and Ainsworth, E.A. 2010. Spring leaf flush in aspen (Populus tremuloides) clones is altered by long-term growth at elevated carbon dioxide and elevated ozone concentration. Environmental Pollution 158: 1023-1028.
McGrath et al. report that the trees in the elevated CO2 plots showed a 36% stimulation of leaf area index, while the trees in the elevated O3 plots actually showed a 20% reduction in LAI. In addition, they say that the photosynthetic operating efficiency of the CO2-enriched aspen leaves was significantly enhanced by a whopping 51%. Given these findings, atmospheric CO2 enrichment appears to provide youthful aspen trees with a great head start to the growing season.
Augspurger, C.K. 2008. Early spring leaf out enhances growth and survival of saplings in a temperate deciduous forest. Oecologia 156: 281-286.