Declining tree growth rates despite increasing water-use efficiency under elevated CO2 reveals a possible global overestimation of CO2 fertilization effect. Issue 10 (October 2022)

• Record Type: Journal Article
• Authors: Laffitte, Benjamin; Seyler, Barnabas C.; Wang, Wenzhi; Li, Pengbo; Du, Jie; Tang, Ya
• Is Part Of: Heliyon. Volume 8:Issue 10(2022)
• Publication Date: 2022-10
• Subjects: Basal area increment -- CO2 fertilization effect -- Dendrochronology -- Elevated CO2 -- Intrinsic water-use efficiency -- Jiuzhaigou national nature reserve; Research -- Periodicals; Medical sciences -- Periodicals; Natural history -- Periodicals; Social sciences -- Periodicals; Earth sciences -- Periodicals; Physical sciences -- Periodicals; 507.2
• DOI: 10.1016/j.heliyon.2022.e11219
• Languages: English
• ISSNs: 2405-8440

Abstract

Abstract: Though rising atmospheric CO2 concentrations (Ca ) harm the environment and society, they may also raise photosynthetic rates and enhance intrinsic water-use efficiency (iWUE). Numerous short-term studies have investigated tree growth under elevated CO2 (eCO2 ) conditions, but no long-duration study has investigated eCO2 impacts on tree growth and iWUE under natural conditions. Utilizing a new dendrochronological experimental design in a heavily-touristed nature preserve in Southwest China (Jiuzhaigou National Nature Reserve), we compared tree growth (e.g., basal area increment) and iWUE in two biophysically and environmentally similar valleys with contrasting anthropogenic activities. Trees in the control valley with ambient CO2 benefited from increasing Ca, possibly due to the CO2 fertilization effect and optimal environmental conditions. However, trees in the treatment valley with intensive tourism experienced comparatively higher localized eCO2 and growth rate declines. While iWUE increased (1959–2017) in the control (25.3%) and treatment sites (47.8%), declining tree growth rates in the treatment site was likely because comparatively extreme CO2 exposure levels encouraged stomatal closures. As the first long-term study investigating eCO2 impacts on tree growth and iWUE under natural conditions, we demonstrate that increased forest iWUE is unlikely to overcome negative drought stress and rising temperature impacts. Thus, forest potential for mitigating eCO2 and global climate change is likely overestimated, particularly under dry temperate conditions. Graphical abstract: Image 1 Abstract : Basal area increment; CO2 fertilization effect; Dendrochronology; Elevated CO2 ; Intrinsic water-use efficiency; Jiuzhaigou national nature reserve.