Abstract
Abstract. Biogenic volatile organic compound (BVOC) emission factors (Es) underpin air quality and climate models, yet current databases intermingle data from both seedlings and mature trees and from two enclosure techniques, leaf cuvettes and dynamic branch chambers, whose comparability has rarely been rigorously tested. Here we quantified BVOC emissions from Eucalyptus urophylla by pairing the two methods on a statistically representative number of 2-month-old seedlings in the laboratory and 2-year-old trees measured at a managed plantations in subtropical China. Leaf-cuvette and branch-chamber determination of isoprene Es matched within 5 % for both age classes, demonstrating method equivalence. In contrast, tree age exerted a significant impact on both the magnitude and speciation of emissions. Seedlings emitted ~50 % more isoprene and were enriched in cyclic monoterpenes like α-pinene and 1,8-cineole, whereas field-grown trees shifted toward highly reactive acyclic monoterpenes, with β-ocimenes accounted for over 85 % of the terpene flux. These ontogenetic shifts imply that one-third of the entries in global Es compilations, which are derived from seedling studies, likely overestimate local isoprene fluxes while under-representing the atmospheric reactivity of mature canopies. Our results validate the use of either chamber type for measuring isoprene Es, highlight the need for improved analytical sensitivity before extending this equivalence to terpenes, and call for systematic, large-sample, branch-level measurements of adult trees to produce representative Es values. Incorporating age-resolved emission factors into models will refine estimates of ozone and secondary organic aerosol formation in fast-growing subtropical plantations and other managed forests worldwide.
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Claims 7
Claim · model-written summary
Leaf cuvette and branch chamber estimates of isoprene emissions matched within 5% at both ages.
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Verbatim
e0“Leaf-cuvette and branch-chamber determination of isoprene Es matched within 5 % for both age classes”
Claim · model-written summary
Tree age significantly affected emission magnitude and speciation.
Not reportedTaxonDirection
Verbatim
e0“tree age exerted a significant impact on both the magnitude and speciation of emissions.”
Claim · model-written summary
Seedlings emitted about 50% more isoprene than trees.
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Verbatim
e0“Seedlings emitted ~50 % more isoprene”
Claim · model-written summary
Seedlings were enriched in α-pinene and 1,8-cineole.
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Verbatim
e0“were enriched in cyclic monoterpenes like α-pinene and 1,8-cineole”
Claim · model-written summary
Field grown trees shifted toward acyclic monoterpenes.
- Organ / stage
- field-grown treese0
- Outcome
- highly reactive acyclic monoterpenese0
- Direction
- shifted towarde0
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Verbatim
e0“field-grown trees shifted toward highly reactive acyclic monoterpenes”
Claim · model-written summary
β-ocimenes accounted for over 85% of terpene flux in field trees.
Not reportedTaxon
Verbatim
e0“β-ocimenes accounted for over 85 % of the terpene flux.”
Claim · model-written summary
The authors recommend large sample branch measurements of adult trees.
- Outcome
- systematic, large-sample, branch-level measurements of adult treese0
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Verbatim
e0“call for systematic, large-sample, branch-level measurements of adult trees to produce representative Es values.”