ONGOING:
4) The project “Cost-effective methods for tracking large scale vegetation physiology: Participatory phase and pilot experiments”, is a two year project (Oct 2016 – Sep 2018) funded by the Academy of Finland under the key Funding Call. The goal of the project is to to evaluate the feasibility and potential of SIF and PRI for tracking large scale vegetation physiology, and to identify novel and cost-effective methods to optimize vegetation management in real-case scenarios.
Society faces the combined challenge of a rising population increasingly concentrated in urban areas. Food production needs to increase sustainably in response to this challenge by the optimal use of water, fertilizers and pesticides. In addition urban forests are now valued as key ecosystem service providers, with potential to reduce city air pollution levels, temperatures and human stress levels. These developments require the adoption of modern vegetation management practices to rapidly and accurately monitor the dynamic health status of vegetation.
With the advent of unmanned aerial vehicles (UAVs) and hyperspectral imaging systems it is now possible to acquire optical information from vegetation anywhere and anytime. Optical indices such as greenness are being applied in the context of precision agriculture to estimate plant biomass or nitrogen content. However, variations in greenness (e.g. the yellowing of diseased leaves) reflect only the slow response of plants to stress making them less suitable for vegetation monitoring. Vegetation generates additional optical signals that cannot be seen with the naked eye and require the use of hyperspectral systems, e.g. the emission of solar-induced chlorophyll fluorescence (SIF) or the photochemical reflectance index (PRI). In contrast to greenness, SIF and PRI respond instantaneously to the plant’s physiological status making these indices particularly suitable for pre-visual stress detection and optimization of fertilizer, irrigation or pesticide application. Despite the intrinsic potential of SIF and PRI their use remains stuck at the basic research level or focused on scientific activities, largely due to the difficulties of interpreting the data.
In this project we will apply our models and know-how to evaluate the feasibility and cost-effectiveness of SIF and the PRI for tracking large scale vegetation physiology in a number of real-case scenarios. Together with end-users and key stakeholders, we have identified real case-studies (both in city parks and farms) that will be used to conduct pilot activities during the project. Stakeholders and end-users from applied research institutes, industry, service and agricultural sectors, as well as city parks departments will be involved in the project.
Budget: c. 300 k€
3) FLUO-SYNTHESIS (Sept 2015 – Aug 2020). FLUO-SYNTHESIS (From Chlorophyll Fluorescence to Photosynthesis: Upscaling the Link) is a 5-year project funded by the Academy of Finland as part of an Academy Research Fellowship granted to Dr. Porcar-Castell. The goal of the project is to generate new mechanistic understanding and develop new methodology to quantitatively interpret solar-induced fluorescence in terms of photosynthesis.
The relationship between fluorescence and photosynthesis is well known at the leaf level, over short periods of time, and using active fluorescence methods (e.g. PAM fluorometers). Yet, interpretation of solar-induced fluorescence involves passive methods, seasonal changes, and canopy-scale measurements where leaves with multiple optical traits add to the integrated canopy signal. For example, the photosynthetic energy partitioning snapshot presented in the figure below is expected to differ across space, time, species, and stress factors affecting the relationship between fluorescence and carbon assimilation. In FLUO-SYNTHESIS we will characterize and model this variability.
Figure. Photosynthetic energy partitioning in a leaf. Incident photosynthetically active radiation (PAR) is partitioned between (a) reflected, transmitted and absorbed PAR (APAR). Pigment molecules responsible for the absorbed PAR (APAR) can be associated either with photosystem II (PSII) or photosystem I (PSI) (b) each with a relative absorption cross section: α (PSII), and β (PSI). Energy absorbed by PSII (c) can be used to run the Linear Electron Transport chain (LET), can be thermally dissipated as heat (NPQ), or re-emitted as chlorophyll fluorescence; similarly, energy absorbed by PSI (d) can be used to operate the LET chain, the Cyclic Electron Transport (CET), be thermally dissipated as heat (NPQ?), or re-emitted as chlorophyll fluorescence. Partitioning between LET and CET (e) can be used, among others, to adjust the ratio of ATP to NADPH depending on metabolic demands. Resulting ATP and NADPH is used (f): to assimilate atmospheric CO2 (carboxylation), to run photorespiration; or used by alternative energy sinks.
Budget: c. 1 M€.
PAST PROJECTS
2) The project “A generic radiative transfer model for the estimation of canopy photosynthetic light use efficiency via the photochemical reflectance index: integrating physical and physiological factors” (Jan 2013 – Apr 2016) is a three year project funded by the University of Helsinki (PI. Dr. Porcar-Castell). The aim of the project was to adapt a radiative transfer model for the estimation of canopy photosynthetic light use efficiency via the photochemical reflectance index that integrates both physical and physiological factors. To do this we started by coupling a Leaf radiative transfer and process based model (Atherton et al. 2016) and also characterized the background spatial variation in leaf level optical traits in boreal species (Atherton et al. In review). Upscaling work is ongoing.
Budget: 145 k€.
1) The project “Towards a mechanistic approach to remote sensing of gross primary production (GPP)” was a 3 year postdoctoral project funded by the Academy of Finland (Jan 2011- Dec 2013) (PI. Porcar-Castell). We evaluated the potential of integrating different sources of optical data to interpret seasonal variations in photosynthetic light use efficiency and gas exchange. Although a part of the data is still being analyzed, one of the main outcomes was that the integration of PRI and fluorescence data at the seasonal scale is complicated by the decoupling between PRI and non-photochemical quenching (NPQ) under severe cold stress (Porcar-Castell et al. 2012, Oecologia).
Budget: c. 308 k€.