Water use and carbon accumulation in a pine forest under elevated atmospheric [CO2]

The Duke Forest Free-Air CO 2 Enrichment (FACE) experiment enriched the air (eCO 2 ) in 30 m diameter plots to a constant +200 ppm CO 2 , from 1994 to 2010. The experiment was aimed at testing hypotheses generated from studies on small individuals and evaluating whether scaling was a simple matter of accounting for size differences, and providing data to inform and test models used for prediction of forest behavior in the future. testing hypotheses generated from studies on small individuals and evaluating whether scaling was a simple matter of accounting for size differences, and providing data to inform and test models used for prediction of forest behavior in the future. The site was planted into Pinus taeda in 1984 but included volunteers of ~40 woody species comprising up to 50% of the leaf area index ( L ) in the poorer, more elevated plots of the relatively flat site. At the end of the study, dominant trees had reached a diameter of ~35 cm and a height of ~25 m. I will present several dominating convictions about forest response to eCO 2 and contrast these with the ultimate results from this and other FACE studies. In a nutshell, L reflects the intra-site variation in soil resources, and therefore the ability of the different patches of the stand to respond to eCO 2 ; in turn, the more a patch was able to respond, the more L increased. Under eCO 2 , net primary production (NPP) of canopy trees increased at a given L , but overtime L increased (~18%) and NPP was mostly explained by the variation of L across the treatments. Despite the increase of L , little eCO 2 effect was observed on any component of the water cycle. As context, I will contrast the direct effect of eCO 2 on carbon accumulation at the site with the indirect effect of climate change on storm-related carbon transfer to the detrital pool.