Effects of elevated CO2 on forest community composition and succession
My work included investigating effects of elevated atmospheric CO2 on juvenile trees and other woody vegetation growing in the Duke University Free-Air Carbon Dioxide Enrichment (FACE) experiment. I focused on early life-history stages of forest trees because they play an essential role in explaining diverse assemblages of tree species. These plants, growing at ambient (~370 μl/l) and elevated (~570 μl/l) CO2 concentrations, represent twenty-eight species comprising tree, vine, and shrub functional groups as well as several shade-tolerance classes. A portion of this work is a Mohan et all. 2007 “Long-term CO2 enrichment of a forest ecosystem: implications for forest regeneration and succession”.
Although shade-intolerant trees, particularly nitrogen-fixing Robinia pseudoacacia, often grew faster under high CO2 they also had very low survivorship rates. I found that elevated CO2 greatly enhanced the population biomass of tree species with high survivorship under low light conditions. These species were shade-tolerant, slow-growing taxa at maturity, suggesting that future temperate forests may exhibit a regeneration bias towards less-productive tree species. However, the effect of elevated CO2 on individual tree growth was small relative to the random variability within populations.