Remote sensing of solar induced fluorescence and the Photochemical Reflectance Index (PRI) for carbon uptake in two contrasting forest ecosystem types

The increase in concentration of carbon dioxide (CO2) in the atmosphere and its contribution to global warming is one of the most urgent of environmental issues. The rise in atmospheric CO2 has been principally ascribed to the burning of fossil fuels and tropical deforestation. Around 45% of the estimated emissions of CO2 are accounted for by the increase in atmospheric CO2, but the remainder is largely unaccounted for and it is believed that the terrestrial biosphere and the oceans are taking up the remainder. A number of scientific studies suggest that it is the vegetation that is primarily responsible for taking up this excess CO2, yet these estimates are uncertain, as well as an understanding of the processes that drive them. The aim of this work is to specifically improve estimates of the processes of photosynthesis, and stress (such as lack of water, and heat, for example) using remote sensing. The direct measurement of the photosynthetic CO2 exchange between the atmosphere and biosphere can be carried out by using advanced systems that include fast responding gas (CO2) analysers. Such systems are already installed globally in a network of over 200 sites and actively collect CO2 flux data over contrasting vegetation types. Whilst these measurements are powerful in that they provide continuous data on photosynthesis of large areas of vegetation, they only represent one point in space and we wish to utilise other methods, namely remote sensing, that can also provide this information yet measure over a much larger geographical area. In a nutshell, global issues with global impact, requires global measurement and this can only be achieved using remote sensing. Within our group we have successfully developed methods to detect changes in the photosynthetic reactions from remote sensing (from aircraft) but have only tested this is a select few ecosystem types. This therefore presents a unique and exciting opportunity to investigate the use of remote sensing for measuring photosynthesis such that we can move towards the reality of 'measuring biology from space', which would be a key breakthrough in photosynthesis research and advance our understanding of the role of vegetation in the terrestrial carbon cycle. This field is particularly exciting because it addresses fundamental scientific and political issues. The Intergovernmental Panel on Climte Change released its final synthesis report which highlighed not only the unequivocal evidence in support of climate warming, but also the impact this will have on terrestrial ecosystems. The proposal is therefore of high importance since it addresses the issue of carbon uptake by vegetation and how it will be affected by the stresses imposed by a changing climate.