Variation in the phenology of photosynthesis among eastern white pine provenances in response to warming

In higher‐latitude trees, temperature and photoperiod control the beginning and end of the photosynthetically active season. Elevated temperature (ET) has advanced spring warming and delayed autumn cooling while photoperiod remains unchanged. We assessed the effects of warming on the length of the p...

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Bibliographic Details
Published in:Global change biology 2020-09, Vol.26 (9), p.5217-5234
Main Authors: Fréchette, Emmanuelle, Chang, Christine Yao‐Yun, Ensminger, Ingo
Format: Article
Language:English
Subjects:
Air temperature
Autumn
Carotenoids
Chlorophyll
chlorophyll fluorescence
chlorophyll/carotenoid index
Chlorophylls
Climate change
Conifers
Cooling effects
eastern white pine (Pinus strobus L.)
elevated temperature
Fluorescence
Gas exchange
High temperature
intraspecific variation
Length
Phenology
photochemical reflectance index
Photochemicals
Photochemistry
Photoperiod
Photoperiods
Photosynthesis
photosynthetic gas exchange
Pigments
Pine needles
Pine trees
Pinus
Pinus strobus
Provenance
provenances
Quenching
Reflectance
Remote monitoring
Seasonal variation
Seasonal variations
Seasons
Seedlings
Spectral reflectance
Spring
Spring (season)
Temperature
temperature‐free‐air‐controlled enhancement (T‐FACE)
Tracking
Zeaxanthin
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Summary:In higher‐latitude trees, temperature and photoperiod control the beginning and end of the photosynthetically active season. Elevated temperature (ET) has advanced spring warming and delayed autumn cooling while photoperiod remains unchanged. We assessed the effects of warming on the length of the photosynthetically active season of three provenances of Pinus strobus L. seedlings from different latitudes, and evaluated the accuracy of the photochemical reflectance index (PRI) and the chlorophyll/carotenoid index (CCI) for tracking the predicted variation in spring and autumn phenology of photosynthesis among provenances. Seedlings from northern, local and southern P. strobus provenances were planted in a temperature‐free‐air‐controlled enhancement (T‐FACE) experiment and exposed to ET (+1.5/3°C; day/night). Over 18 months, we assessed photosynthetic phenology by measuring chlorophyll fluorescence, gas exchange, leaf spectral reflectance and pigment content. During autumn, all seedlings regardless of provenance followed the same sequence of phenological events with the initial downregulation of photosynthesis, followed by the modulation of non‐photochemical quenching and associated adjustments of zeaxanthin pool sizes. However, the timing of autumn downregulation differed between provenances, with delayed onset in the southern provenance (SP) and earlier onset in the northern relative to the local provenance, indicating that photoperiod at the provenance origin is a dominant factor controlling autumn phenology. Experimental warming further delayed the downregulation of photosynthesis during autumn in the SP. A provenance effect during spring was also observed but was generally not significant. The vegetation indices PRI and CCI were both effective at tracking the seasonal variations of energy partitioning in needles and the differences of carotenoid pigments indicative of the stress status of needles. These results demonstrate that PRI and CCI can be useful tools for monitoring conifer phenology and for the remote monitoring of the length of the photosynthetically active season of conifers in a changing climate. At higher latitudes, an extended growing season with earlier greening and delayed autumn senescence is evidence that vegetation responds to climate warming. However, in many tree species, both temperature and photoperiod control the beginning and end of the photosynthetically active season. While temperature increases, photoperiod remains unchanged,
ISSN:1354-1013
1365-2486
DOI:10.1111/gcb.15150