Paper Reviewed
Li, Y., Liu, J., Chen, G., Zhou, G., Huang, W., Yin, G., Zhang, D. and Li, Y. 2015. Water-use efficiency of four native trees under CO2 enrichment and N addition in subtropical model forest ecosystems. Journal of Plant Ecology 8: 411-419.

Working with four native tree species of China (Schima superba, Ormosia pinnatta, Castanopsis hystrix and Acmena acuminatissima) over the period of time from January 2006 to January 2010, Li et al. (2015) studied the effects of an approximate 300 ppm increase in the air's CO2 concentration on the trees' water use efficiency (WUE), which they did within open-top chambers exposed to full light and rain out-of-doors at the South China Botanical Garden of the Chinese Academy of Sciences at Guangzhou, China, either with (CN) or without (CC) added nitrogen (N) fertilization (NH4NO3 applied at a rate of 100 kg N per hectare per year). And what did they thereby learn?

In the words of the eight researchers, "compared to the control, the average increased extents of intrinsic WUE were 98 and 167% in CC and CN treatments for S. superba, 88 and 74% for O. pinnata, 234 and 194% for C. hystrix, and finally, 153 and 81% for A. acuminatissima, which are some pretty incredible increases that likely could not have been achieved by any other means.

And that's one of the reasons we often refer to atmospheric CO2 as "the elixir of life."