Responses of forests in the eastern US to air pollution and climate change

Abstract

The interactions of elevated atmospheric carbon dioxide (CO2) with physical (i.e., precipitation, light, and temperature) and chemical (i.e., ozone (O3), nitrogen and sulfur deposition, and nutrients) environmental factors that affect plant growth have been demonstrated in experiments that simulate managed and natural forest ecosystems in the eastern United States. Elevated atmospheric CO2 has been shown to substantially enhance photosynthesis and carbon gain. The response of a southern tree species, loblolly pine (Pinus taeda L.), to a doubling of ambient CO2 was a 50% increase (to 130%) in the rate of net photosynthesis and a 20% reduction in dark respiration, depending on the study and treatment conditions. Volume change showed similar trends with increases in stem wood volume growth of 52% to 152%. Carbon gain for northern tree species with similar experimental treatments showed a 37% increase in dry weight biomass for trembling aspen (Populus tremuloides Michx.) and a 73% increase in dry weight biomass for yellow poplar (Lirodendron tulipifera L.). The impact of a doubling of atmospheric CO2 on forest net primary productivity at the regional scale indicates a potential increase of 49% in the southeastern United States and an increase of 30-37% in the northeastern United States. © 2003 Elsevier Science Ltd. All rights reserved.