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Kromdijk Group: What can we learn from solar induced fluorescence signals to better constrain gross primary productivity?

NERC / GFC / Other

Supervisor: Wanne Kromdijk (Plant Sciences
Co-Supervisor: Howard Griffiths (Plant Sciences)

Importance of the area of research concerned:

The expansion of the human population is having a severe impact on the biogeochemical carbon cycle, with dramatic feed-forward effects on global climate. To understand and interpret the magnitude of human impact on the carbon cycle, it is imperative to have precise constraints on carbon fluxes through the biosphere. CO2 fluxes transiting the atmosphere-biosphere interface via plant leaves, are representing 40% of global net primary productivity. Resolving carbon fluxes across leaf, canopy, ecosystem and global scales is therefore important to accurately quantify gross primary productivity and constrain effects of climate change on performance of the terrestrial biosphere. At leaf-level, measurements of CO2 and water vapour exchange can be readily used to quantify photosynthetic CO2 fixation. At canopy and ecosystem level, carbon exchange can be modelled based using these leaf-level data, or estimated using eddy-covariance techniques. However, these estimates have relatively large uncertainty bounds and additional proxies to constrain large scale carbon fluxes are desperately needed.

Project summary:

This project aims to improve the predictive value of passive chlorophyll fluorescence for gross primary productivity by characterizing its relationship with plant CO2 exchange at leaf and stand-level. Remotely sensed solar-induced chlorophyll fluorescence signals have been gaining traction as alternative proxies to constrain vegetation carbon fluxes (Meroni et al. 2009). These optical signals have a strong theoretical link with photosynthetic efficiency, and can be exploited for large scale sensing of plant status and functioning (Porcar-Castell et al. 2014). However, in contrast to aforementioned leaf- and canopy-level measurement techniques, the mechanistic framework to interpret the relationship between passive fluorescence and CO2 exchange is still underdeveloped. The results of this project will improve understanding and interpretation of solar induced fluorescence signals.

What will the student do?

The student will design and execute experiments aimed to characterize the relationship between passive fluorescence and CO2 exchange in selected plant species from contrasting functional groups under stressed and non-stressed conditions. The student will use spectrally resolved chlorophyll fluorescence signals and use several complementary fluorescence techniques in parallel (Pulse Amplitude Modulated fluorescence and Laser Induced Fluorescence Transients) to constrain the passive fluorescence proxies. The student will use simulation modelling to interpret the observed relationships.

References:

  • Meroni M, Rossini M, Guanter L, Alonso L, Rascher U, Colombo R, Moreno J 2009. Remote sensing of solar-induced chlorophyll fluorescence: Review of methods and applications. Remote Sensing of Environment 113 (10): 2037-51.
  • Porcar-Castell A, Tyystjärvi E, Atherton J, VanderTol C, Flexas J, Pfűndel EE, Moreno J, Frankenberg C, Berry JA 2014 Linking chlorophyll a fluorescence to photosynthesis for remote sensing applications: mechanisms and challenges. Journal of Experimental Botany 65 (15): 4065-95.

Applying: To the Cambridge NERC C-CLEAR DTP programme: https://nercdtp.esc.cam.ac.uk/

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