Marra, Elena
- Department of Forest Bioeconomy and Technology, Swedish University of Agricultural Sciences
Abstract
Tropospheric ozone (O3) is a pervasive stressor that impairs forest biomass and alters carbon allocation strategies. This studyassessed biomass responses across 17 woody taxa under free-air controlled exposure (FACE), integrating a decade of experimentsconducted with an analogous exposure regime applied to deciduous and evergreen species. The analysis provided a comparativeevaluation of existing flux-based metrics. Statistical analyses revealed consistent reductions in relative total (RTB), aboveground(RTAB), and belowground (RTBB) biomass with increasing O3 uptake in terms of phytotoxic ozone dose (POD1 mmol m−2).Deciduous species reached the 4% biomass reduction threshold (CL4) at lower POD1 levels for RTBB (10.21), RTAB (13.16), andRTB (10.77) and displayed relatively small △POD1 values for RTBB (2.75), RTAB (5.70), and RTB (3.31), where △POD1 representsthe increment in O3 uptake required to reach the CL4 threshold. In contrast, evergreen species showed higher CL4 for RTBB(11.48), RTAB (15.40), and RTB (13.86) and larger △POD1 values for RTBB (8.40), RTAB (12.32), and RTB (10.78), reflecting aslower biomass decline. Contrasting relationships suggest that leaf habit-specific patterns are associated with divergent carbonallocation strategies under O3 stress. In deciduous species, POD1 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. Inconclusion, flux-based metrics provided a biologically robust framework for quantifying O3-induced biomass losses, revealinghigher sensitivity in deciduous species than in evergreens and highlighting the root as the most vulnerable compartment underO3 exposure. The findings should be interpreted considering the spatial and temporal constraints of a single-site FACE experi-ment and the focus on O3 as a stand-alone stressor without interaction effects. Future research should combine O3 uptake withmulti-stressor frameworks to better predict biomass and carbon responses in complex field conditions.
Keywords
biomass allocation indices; carbon allocation; environmental pollution; LIF; O3; POD1; relative biomass; roots
Published in
Global Change Biology
2026, volume: 32, number: 2, article number: e70728
SLU Authors
UKÄ Subject classification
Environmental Sciences
Publication identifier
- DOI: https://doi.org/10.1111/gcb.70728
Permanent link to this page (URI)
https://res.slu.se/id/publ/145968