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| Titel |
Monitoring seasonal and diurnal changes in photosynthetic pigments with automated PRI and NDVI sensors |
| VerfasserIn |
J. A. Gamon, O. Kovalchuck, C. Y. S. Wong, A. Harris, S. R. Garrity |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 13 ; Nr. 12, no. 13 (2015-07-14), S.4149-4159 |
| Datensatznummer |
250118019
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| Publikation (Nr.) |
 copernicus.org/bg-12-4149-2015.pdf |
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| Zusammenfassung |
| The vegetation indices normalized difference vegetation index (NDVI) and
photochemical reflectance index (PRI) provide indicators of pigmentation and
photosynthetic activity that can be used to model photosynthesis from remote
sensing with the light-use-efficiency model. To help develop and validate
this approach, reliable proximal NDVI and PRI sensors have been needed. We
tested new NDVI and PRI sensors, "spectral reflectance sensors" (SRS sensors; recently developed by
Decagon Devices, during spring activation of photosynthetic activity in
evergreen and deciduous stands. We also evaluated two methods of sensor
cross-calibration – one that considered sky conditions (cloud cover) at
midday only, and another that also considered diurnal sun angle effects.
Cross-calibration clearly affected sensor agreement with independent
measurements, with the best method dependent upon the study aim and time
frame (seasonal vs. diurnal). The seasonal patterns of NDVI and PRI differed
for evergreen and deciduous species, demonstrating the complementary nature
of these two indices. Over the spring season, PRI was most strongly
influenced by changing chlorophyll : carotenoid pool sizes, while over the
diurnal timescale, PRI was most affected by the xanthophyll cycle
epoxidation state. This finding demonstrates that the SRS PRI sensors can
resolve different processes affecting PRI over different timescales. The
advent of small, inexpensive, automated PRI and NDVI sensors offers new ways
to explore environmental and physiological constraints on photosynthesis,
and may be particularly well suited for use at flux tower sites. Wider
application of automated sensors could lead to improved integration of flux
and remote sensing approaches for studying photosynthetic carbon uptake, and
could help define the concept of contrasting vegetation optical types. |
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