Work

Can Oxygen Isotopes in Tree Rings Be Used to Detect Stomatal Responses to Global Change?

Year: 2025

Type: article

Abstract: ABSTRACT Stomatal conductance (g s ) regulates CO 2 and water fluxes of plants. Although experiments have shown that g s decreases with elevated CO 2 , it is unclear how g s is responding in situ to long‐term exposures to rising CO 2 and a changing climate. Tree ring isotope analysis provides a unique method to assess tree ecophysiological responses to long‐term exposures of slowly changing environmental conditions. In particular, it has been suggested that changes in g s can potentially be inferred from tree ring stable oxygen isotope ratios (δ 18 O trc ). Several studies have indeed used δ 18 O trc trends to conclude that g s has not significantly changed from pre‐industrial values. However, it remains unclear whether δ 18 O trc is sufficiently sensitive to detect the magnitude of change in g s expected due to CO 2 increases and climatic changes. Here, we evaluate the sensitivity of δ 18 O trc trends to CO 2 and climate induced changes in g s , and to VPD and temperature increases since the beginning of the 20th century, using current theoretical models. We find that temporal changes in g s only significantly affect δ 18 O trc trends when the Péclet effect is present, and then only in dry climates. In contrast to the weak effects of g s on δ 18 O trc trends, we find that temporal increases in VPD and temperature, independent of changes in g s , have far greater contributions to δ 18 O trc trends. Thus, this increasingly popular method should be used with caution, because it is highly challenging to unambiguously attribute trends in δ 18 O trc to changes in g s . Despite current limitations, we recommend how future studies can address these challenges in efforts to detect long‐term g s trends from tree ring records.

Source: Global Change Biology

DOI: 10.1111/gcb.70604

Authors: Imogen Carter, Roel Brienen, Manuel Gloor

Institution: University of Leeds

Language: English

Topic: Tree-ring climate responses

Subfield: Atmospheric Science

Field: Earth and Planetary Sciences

Domain: Physical Sciences

SDG: Climate action

Open Access status: hybrid

Estimated APC paid: $4,550