Declining tree growth rates despite increasing water-use efficiency under elevated CO2 reveals a possible global overestimation of CO2 fertilization effect

A long-term study at Jiuzhaigou Valley, a UNESCO World Heritage Site in Southwest China, reveals that elevated CO2 (eCO2) may not enhance tree growth as previously thought. Despite increasing intrinsic water-use efficiency (iWUE), trees exposed to higher localized eCO2 due to intensive tourism showed declining growth rates, likely due to stomatal closures. This challenges the global overestimation of CO2 fertilization effects on forests, particularly under dry temperate conditions. The research used a novel dendrochronological approach comparing two valleys with contrasting anthropogenic activities, providing new insights into the complex interactions between CO2, climate change, and forest resilience.

Laffitte, B., Seyler, B. C., Wang, W., Li, P., Du, J., & Tang, Y. (2022). Declining tree growth rates despite increasing water-use efficiency under elevated CO2 reveals a possible global overestimation of CO2 fertilization effect. Heliyon, 8(10), e11219. https://doi.org/10.1016/j.heliyon.2022.e11219