Diurnal Changes in Leaf Photochemical Reflectance Index in Two Evergreen Forest Canopies

Matti Mõttus (Corresponding Author), Luiz Aragão, Jaana Bäck, Rocio Hernández-Clemente, Eduardo Eiji Maeda, Vincent Markiet

    Research output: Contribution to journalArticleScientificpeer-review

    4 Citations (Scopus)


    The spectral properties of plant leaves relate to the state of their photosynthetic apparatus and the surrounding environment. An example is the well known photosynthetic downregulation, active on the time scale from minutes to hours, caused by reversible changes in the xanthophyll cycle pigments. These changes affect leaf spectral absorption and are frequently quantified using the photochemical reflectance index (PRI). This index can be used to remotely monitor the photosynthetic status of vegetation, and allows for a global satellite-based measurement of photosynthesis. Such earth observation satellites in near-polar orbits usually cover the same geographical location at the same local solar time at regular intervals. To facilitate the interpretation of these instantaneous remote PRI measurements and upscale them temporally, we measured the daily course of leaf PRI in two evergreen biomes—a European boreal forest and an Amazon rainforest. The daily course of PRI was different for the two locations: At the Amazonian forest, the PRI of Manilkara elata leaves was correlated with the average photosynthetic photon flux density (PPFD) (R2 = 0.59, p < 0.01) of the 40 minutes preceding the leaf measurement. In the boreal location, the variations in Pinus sylvestris needle PRI were only weakly (R2 = 0.27, p < 0.05) correlated with mean PPFD of the preceding two hours; for Betula pendula, the correlation was insignificant (p > 0.5) regardless of the averaging period. The measured daily PRI curves were specific to species and/or environmental conditions. Hence, for a proper interpretation of satellite-measured instantaneous photosynthesis, the scaling of PRI measurements should be supported with information on its correlation with PPFD.
    Original languageEnglish
    Pages (from-to)2236-2243
    JournalIEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
    Issue number7
    Publication statusPublished - Jul 2019
    MoE publication typeA1 Journal article-refereed


    This work was supported in part by the Academy of Finland under Grants 266152, 272989, 202633, 317387, and 318252, in part by the Finnish Centre of Excellence in Atmospheric Sciences under the Academy of Finland Grant 272041, and in part by the ICOS ERIC: Horizon2020 under Project ACTRIS, eLTER.


    • Amazon rainforest
    • Betula pendula
    • boreal forest
    • light use efficiency
    • Manilkara elata
    • photochemical reflectance index (PRI)
    • pinus sylvestris


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