Decoupling of greenness and photosynthesis regulates phenological shifts across Australian ecosystems

Xue, J; Renzullo, LJ; Huete, A

Decoupling of greenness and photosynthesis regulates phenological shifts across Australian ecosystems

Xue, J

Renzullo, LJ Huete, A

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Publisher:: Elsevier
Publication Type:: Journal Article
Citation:: Agricultural and Forest Meteorology, 2026, 386, pp. 111253
Issue Date:: 2026-07

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Field	Value	Language
dc.contributor.author	Xue, J https://orcid.org/0000-0003-2136-771X
dc.contributor.author	Renzullo, LJ
dc.contributor.author	Huete, A https://orcid.org/0000-0003-2809-2376
dc.date.accessioned	2026-06-01T01:49:17Z
dc.date.available	2026-06-01T01:49:17Z
dc.date.issued	2026-07
dc.identifier.citation	Agricultural and Forest Meteorology, 2026, 386, pp. 111253
dc.identifier.issn	0168-1923
dc.identifier.uri	http://hdl.handle.net/10453/195197
dc.description.abstract	The complex coupling between structural greenness and functional photosynthesis represents a critical interaction underlying uncertainties in the terrestrial carbon cycle. Greenness-based indicators, such as the leaf area index (LAI) and reflectance-derived indices, represent structural signals of canopy state but often fail to capture the spatiotemporal variations of photosynthetic function. In recent years, solar-induced chlorophyll fluorescence (SIF), as a direct remote-sensing proxy of photosynthesis, has provided a new avenue for exploring vegetation structure–function relationships. In this study, we treated SIF as a functional signal and greenness proxies as structural signals and examined when and where these signals were coupled (i.e., varied synchronously) or decoupled (i.e., differed in timing or magnitude) across Australia using multi-source remote sensing data. We then quantified the spatial variability of SIF–greenness coupling, assessed its associations with environmental and biological factors, and evaluated how variations in coupling accounted for discrepancies between structure- and function-based phenology. Our results indicated that the coupling between vegetation structure and function was primarily associated with vegetation composition and environmental aridity. In herbaceous ecosystems, low soil moisture (SMC) and high vapor pressure deficit (VPD) were linked to stronger coupling between greenness and photosynthesis. With increasing woody fraction (f_woody), the importance of SMC over VPD in influencing greenness–photosynthesis coupling became more pronounced. The relative roles of hydroclimatic and biological factors in greenness–photosynthesis coupling varied with the physical nature of each greenness indicator. Increasing decoupling between vegetation structure and function led to later peaks and shorter growing seasons in greenness-based phenology compared with SIF-based phenology, and these differences intensified with stronger decoupling. These findings advance the understanding of how environmental and biological factors are associated with vegetation structure–function coupling and its implications for phenology and carbon cycle modeling.
dc.language	en
dc.publisher	Elsevier
dc.relation	http://purl.org/au-research/grants/arc/DP210100347
dc.relation	Bureau of Meteorology3888-2023-24
dc.relation.ispartof	Agricultural and Forest Meteorology
dc.relation.isbasedon	10.1016/j.agrformet.2026.111253
dc.rights	info:eu-repo/semantics/openAccess
dc.subject	04 Earth Sciences, 06 Biological Sciences, 07 Agricultural and Veterinary Sciences
dc.subject.classification	Meteorology & Atmospheric Sciences
dc.subject.classification	30 Agricultural, veterinary and food sciences
dc.subject.classification	31 Biological sciences
dc.subject.classification	37 Earth sciences
dc.title	Decoupling of greenness and photosynthesis regulates phenological shifts across Australian ecosystems
dc.type	Journal Article
utslib.citation.volume	386
utslib.for	04 Earth Sciences
utslib.for	06 Biological Sciences
utslib.for	07 Agricultural and Veterinary Sciences
pubs.organisational-group	University of Technology Sydney
pubs.organisational-group	University of Technology Sydney/Faculty of Engineering and Information Technology
pubs.organisational-group	University of Technology Sydney/Faculty of Science
pubs.organisational-group	University of Technology Sydney/Faculty of Science/School of Life Sciences
pubs.organisational-group	University of Technology Sydney/UTS Groups
pubs.organisational-group	University of Technology Sydney/UTS Groups/Centre for Advanced Modelling and Geospatial lnformation Systems (CAMGIS)
pubs.organisational-group	University of Technology Sydney/UTS Groups/AgHort Deep Sector Engagement Area
utslib.copyright.status	open_access	*
dc.rights.license	This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0). To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/
dc.date.updated	2026-06-01T01:49:15Z
pubs.publication-status	Accepted
pubs.volume	386

Abstract:

The complex coupling between structural greenness and functional photosynthesis represents a critical interaction underlying uncertainties in the terrestrial carbon cycle. Greenness-based indicators, such as the leaf area index (LAI) and reflectance-derived indices, represent structural signals of canopy state but often fail to capture the spatiotemporal variations of photosynthetic function. In recent years, solar-induced chlorophyll fluorescence (SIF), as a direct remote-sensing proxy of photosynthesis, has provided a new avenue for exploring vegetation structure–function relationships. In this study, we treated SIF as a functional signal and greenness proxies as structural signals and examined when and where these signals were coupled (i.e., varied synchronously) or decoupled (i.e., differed in timing or magnitude) across Australia using multi-source remote sensing data. We then quantified the spatial variability of SIF–greenness coupling, assessed its associations with environmental and biological factors, and evaluated how variations in coupling accounted for discrepancies between structure- and function-based phenology. Our results indicated that the coupling between vegetation structure and function was primarily associated with vegetation composition and environmental aridity. In herbaceous ecosystems, low soil moisture (SMC) and high vapor pressure deficit (VPD) were linked to stronger coupling between greenness and photosynthesis. With increasing woody fraction (f_woody), the importance of SMC over VPD in influencing greenness–photosynthesis coupling became more pronounced. The relative roles of hydroclimatic and biological factors in greenness–photosynthesis coupling varied with the physical nature of each greenness indicator. Increasing decoupling between vegetation structure and function led to later peaks and shorter growing seasons in greenness-based phenology compared with SIF-based phenology, and these differences intensified with stronger decoupling. These findings advance the understanding of how environmental and biological factors are associated with vegetation structure–function coupling and its implications for phenology and carbon cycle modeling.

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http://hdl.handle.net/10453/195197