What question did this study set out to answer?

This research aims to evaluate how ozone exposure affects biomass in different tree species over a decade.

February 2, 2026Global Change Biology2 citationsOpen Access

Tree Biomass Sensitivity to Ozone Exposure: Insights From a Decade of Free‐Air Experiments

AGAnnesha GhoshCentral University of Jharkhand AVAndrea VivianoInstitute of Ecosystem Study EPElena PaolettiInstitute of Ecosystem Study

Key Points

This research aims to evaluate how ozone exposure affects biomass in different tree species over a decade.
Conducted free-air controlled exposure (FACE) experiments on 17 woody taxa.
Integrated ten years of data to analyze biomass responses to ozone.
Utilized flux-based metrics for evaluation and statistical analyses.
Ozone exposure led to significant reductions in total, aboveground, and belowground biomass.
Deciduous species showed a lower phytotoxic ozone dose threshold for biomass reduction compared to evergreens.
Leaf habit influenced carbon allocation strategies under ozone stress.

Abstract

ABSTRACT Tropospheric ozone (O 3 ) is a pervasive stressor that impairs forest biomass and alters carbon allocation strategies. This study assessed biomass responses across 17 woody taxa under free‐air controlled exposure (FACE), integrating a decade of experiments conducted with an analogous exposure regime applied to deciduous and evergreen species. The analysis provided a comparative evaluation of existing flux‐based metrics. Statistical analyses revealed consistent reductions in relative total (RTB), aboveground (RTAB), and belowground (RTBB) biomass with increasing O 3 uptake in terms of phytotoxic ozone dose (POD 1 mmol m −2 ). Deciduous species reached the 4% biomass reduction threshold (CL 4 ) at lower POD 1 levels for RTBB (10.21), RTAB (13.16), and RTB (10.77) and displayed relatively small values for RTBB (2.75), RTAB (5.70), and RTB (3.31), where represents the increment in O 3 uptake required to reach the CL 4 threshold. In contrast, evergreen species showed higher CL 4 for RTBB (11.48), RTAB (15.40), and RTB (13.86) and larger values for RTBB (8.40), RTAB (12.32), and RTB (10.78), reflecting a slower biomass decline. Contrasting relationships suggest that leaf habit‐specific patterns are associated with divergent carbon allocation strategies under O 3 stress. In deciduous species, POD 1 and Leaf Index Flux (LIF) were negatively correlated with shoot‐to‐root ratio (S/R), whereas in evergreen species, both indices were positively correlated with leaf area ratio (LAR) and S/R. In conclusion, flux‐based metrics provided a biologically robust framework for quantifying O 3 ‐induced biomass losses, revealing higher sensitivity in deciduous species than in evergreens and highlighting the root as the most vulnerable compartment under O 3 exposure. The findings should be interpreted considering the spatial and temporal constraints of a single‐site FACE experiment and the focus on O 3 as a stand‐alone stressor without interaction effects. Future research should combine O 3 uptake with multi‐stressor frameworks to better predict biomass and carbon responses in complex field conditions.

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