Post-CO2 Enrichment Effects on Canopy Leaf Area Index

The IPCC has forecasted that carbon dioxide emissions will continue to rise over the next 50 years. The effect of increasing carbon dioxide levels on forest productivity is still minimally understood. Leaf Area Index (LAI) is a primary indicator of photosynthetic potentials. Photosynthesis is the primary driver of tree growth providing sugars and carbohydrates needed for producing biomass. Biomass production rate is relevant to a variety of forestry activities such as silviculture, wildlife management, forest management, and timber management. McCarthy et al. (2007) demonstrated that increased carbon dioxide concentrations at the Duke Free-Air CO2 Enrichment (FACE) experiment in a loblolly pine plantation (with 40 naturally regenerating woody species) increased LAI during canopy closure, but enriched plots were more sensitive to severe weather events. The research presented here, continues the study for two years after enrichment was terminated, found that the effect of enrichment on LAI, on both native-fertility and fertilized soils, was short, disappearing immediately following termination. This demonstrates that higher LAI under elevated CO2 was dependent on higher photosynthesis, rather than changes in long-term ecosystem processes.