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Assessment of the relationship between the Photochemical Reflectance Index and Light Use Efficiency : a study of its seasonal and diurnal variation in a sub-arctic birch forest, Abisko, Sweden

Lindevall, Elsa LU (2016) In Student thesis series INES NGEK01 20161
Dept of Physical Geography and Ecosystem Science
Abstract
Photosynthesis, which describes the uptake of carbon from the atmosphere by vegetation, is key to the natural mitigation of anthropogenic climate change. Its accurate assessment is therefore of vital importance for correct estimates of the global carbon balance and the understanding of global carbon dynamics. This uptake of carbon is referred to as the gross primary productivity (GPP) and can be remotely sensed by utilising models that are based on the concept of light use efficiency (LUE). However, LUE is difficult to derive directly from remote sensing and therefore alternative approaches has been suggested for its derivation. One such approach is the photochemical reflectance index (PRI) which measures the reflectance signal of the... (More)
Photosynthesis, which describes the uptake of carbon from the atmosphere by vegetation, is key to the natural mitigation of anthropogenic climate change. Its accurate assessment is therefore of vital importance for correct estimates of the global carbon balance and the understanding of global carbon dynamics. This uptake of carbon is referred to as the gross primary productivity (GPP) and can be remotely sensed by utilising models that are based on the concept of light use efficiency (LUE). However, LUE is difficult to derive directly from remote sensing and therefore alternative approaches has been suggested for its derivation. One such approach is the photochemical reflectance index (PRI) which measures the reflectance signal of the photoprotective mechanism of the xanthophyll cycle. Even though the PRI and LUE has been shown to be correlated, no generalised relationship has yet been established and more research needs to be conducted for different species, climates and temporal scales in order for this to be achieved. This report shows that for a birch forest in a sub-arctic climate, PRI does not approximate LUE over diurnal and seasonal time scales. The correlation between PRI and LUE were generally higher over the seasonal time scale compared to the diurnal analysis, which exhibited varying correlations throughout the season. The majority of these correlations were not significant (p<0.05), suggesting that PRI cannot be considered as a proxy for LUE in these environments. This contradicts the few studies conducted for other deciduous forests in sub-arctic climates and the research field of PRI as a whole. Therefore, it is likely that it is the design of the study that gives rise to these results and not that the relationship between PRI and LUE does not hold true. The findings of this study therefore comply with and contribute to the body of evidence that suggest that PRI is a sensitive index, highly influenced by external factors. (Less)
Abstract (Swedish)
Fotosyntes, vilket beskriver upptaget av koldioxid från atmosfären av vegetationen, är nyckeln till den naturliga förmildringen av den antropogena klimatförändringen. Dess korrekta skattning är därför av avgörande betydelse för korrekta bedömningar av den globala kolbalansen och förståelsen av det globala kolets kretslopp. Detta upptag av kol kallas bruttoprimärproduktionen (Gross Primary Productivity; GPP) och kan fjärranalyseras genom att utnyttja modeller som är baserade på konceptet av fotosyntetisk effektivitet (Light Use Efficiency; LUE). Det är dock svårt att härleda LUE direkt från fjärranalys och därför har alternativa metoder föreslagits för dess härledning. Ett sådant tillvägagångssätt är det fotokemiska reflexions indexet... (More)
Fotosyntes, vilket beskriver upptaget av koldioxid från atmosfären av vegetationen, är nyckeln till den naturliga förmildringen av den antropogena klimatförändringen. Dess korrekta skattning är därför av avgörande betydelse för korrekta bedömningar av den globala kolbalansen och förståelsen av det globala kolets kretslopp. Detta upptag av kol kallas bruttoprimärproduktionen (Gross Primary Productivity; GPP) och kan fjärranalyseras genom att utnyttja modeller som är baserade på konceptet av fotosyntetisk effektivitet (Light Use Efficiency; LUE). Det är dock svårt att härleda LUE direkt från fjärranalys och därför har alternativa metoder föreslagits för dess härledning. Ett sådant tillvägagångssätt är det fotokemiska reflexions indexet (Photochemical Reflectance Index; PRI), som mäter reflexionen av den ljusskyddande mekanismen xantofyll cykeln. Trots att PRI och LUE har visat sig vara korrelerade, har inget allmänt samband ännu fastställts och mer forskning måste genomföras för olika arter, klimat och tidsskalor för att detta skall kunna uppnås. Denna rapport visar att för en björkskog i ett subarktiskt klimat, approximerar inte PRI LUE över de dagliga eller säsongsmässiga tidsskalorna. Korrelationen mellan PRI och LUE var i allmänhet högre för den säsongsmässiga tidsskalan jämfört med dygnsanalysen, som uppvisade varierande korrelationer under hela säsongen. Majoriteten av dessa korrelationer var inte signifikant (p<0,05), vilket tyder på att PRI inte kan betraktas som ett substitut för LUE i dessa miljöer. Detta motsäger de få studier som genomförts för andra lövskogar i subarktiska klimat och forskningsområdet om PRI som helhet. Därför är det troligt att det är utformningen av denna studie som ger upphov till dessa resultat och inte att förhållandet mellan PRI och LUE inte överensstämmer. Resultaten av denna studie bidrar därför till den mängd bevis som tyder på att PRI är ett känsligt index som i hög grad påverkas av yttre faktorer. (Less)
Please use this url to cite or link to this publication:
author
Lindevall, Elsa LU
supervisor
organization
course
NGEK01 20161
year
type
M2 - Bachelor Degree
subject
keywords
PRI, LUE, seasonal variability, diurnal variability
publication/series
Student thesis series INES
report number
374
language
English
id
8878914
date added to LUP
2016-06-08 16:50:20
date last changed
2016-06-08 16:50:20
@misc{8878914,
  abstract     = {Photosynthesis, which describes the uptake of carbon from the atmosphere by vegetation, is key to the natural mitigation of anthropogenic climate change. Its accurate assessment is therefore of vital importance for correct estimates of the global carbon balance and the understanding of global carbon dynamics. This uptake of carbon is referred to as the gross primary productivity (GPP) and can be remotely sensed by utilising models that are based on the concept of light use efficiency (LUE). However, LUE is difficult to derive directly from remote sensing and therefore alternative approaches has been suggested for its derivation. One such approach is the photochemical reflectance index (PRI) which measures the reflectance signal of the photoprotective mechanism of the xanthophyll cycle. Even though the PRI and LUE has been shown to be correlated, no generalised relationship has yet been established and more research needs to be conducted for different species, climates and temporal scales in order for this to be achieved. This report shows that for a birch forest in a sub-arctic climate, PRI does not approximate LUE over diurnal and seasonal time scales. The correlation between PRI and LUE were generally higher over the seasonal time scale compared to the diurnal analysis, which exhibited varying correlations throughout the season. The majority of these correlations were not significant (p<0.05), suggesting that PRI cannot be considered as a proxy for LUE in these environments. This contradicts the few studies conducted for other deciduous forests in sub-arctic climates and the research field of PRI as a whole. Therefore, it is likely that it is the design of the study that gives rise to these results and not that the relationship between PRI and LUE does not hold true. The findings of this study therefore comply with and contribute to the body of evidence that suggest that PRI is a sensitive index, highly influenced by external factors.},
  author       = {Lindevall, Elsa},
  keyword      = {PRI,LUE,seasonal variability,diurnal variability},
  language     = {eng},
  note         = {Student Paper},
  series       = {Student thesis series INES},
  title        = {Assessment of the relationship between the Photochemical Reflectance Index and Light Use Efficiency : a study of its seasonal and diurnal variation in a sub-arctic birch forest, Abisko, Sweden},
  year         = {2016},
}