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Abstract Detail



Physiological Section

Junker, Laura [1], Ensminger, Ingo [1].

Assessing autumn physiology of Acer saccharum using spectral reflectance and digital image vegetation indices.

Remote-sensing techniques are increasingly used to monitor ecosystem phenology. Phenological observations are used to track long term climatic changes and improve ecosystem productivity models. Sugar maple trees display colorful autumn leaves which indicate leaf senescence and decreased photosynthetic efficiency. We are interested in autumn physiology and how changes of photosynthetic pigments can be assessed by vegetation indices derived from spectral reflectance measurements and digital repeat images. We hypothesized that decreasing photosynthetic efficiency is reflected by senescence-associated changes in leaf pigments content which influence leaf spectral properties and allow the monitoring of fall phenology using image analysis and spectral reflectance measurements. We studied chlorophyll fluorescence, pigment content and leaf spectral properties of green, yellow, orange and red leaves which were simultaneously sampled in autumn representing stages of advancing senescence in comparison to non-senescent summer leaves. Photosynthetic efficiency decayed with advancing senescence, as is represented by decreasing chlorophyll content. Carotenoid degradation is slower, with delayed degradation of photoprotective antheraxanthing and zeaxanthin compared to other carotenoids. Antioxidant anthocyanins and tocopherols accumulated during senescence. These changes in leaf pigment content caused a gradual change of leaf color from green over yellow to red, and went along with a decline in photosynthetic efficiency. Vegetation indices varied in their suitability to represent physiological changes. Digital image analysis proved useful to represent gradual changes during autumn, but threshold values representing the phenological onset of senescence can easily be derived from both methods.


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1 - University of Toronto, Cell and Systems Biology, 3359 Mississauga Road, Mississauga, ON, L5L1C6, Canada

Keywords:
Sugar maple
Photosynthesis
Photoprotective mechanisms
Chlorophyll fluorescence
Photosynthetic gas exchange
Photosynthetic pigments
Digital repeat photography
Spectral reflectance
Remote sensing
Phenolgy
Leaf senescence.

Presentation Type: Oral Paper:Papers for Sections
Session: 53
Location: Salon 16/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 3:45 PM
Number: 53007
Abstract ID:131
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize,CSPB President's Award for Best Student Presentation


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