We’ve brought a range of instruments with us to the Arctic, to simultaneously measure plant photosynthesis and remote sensing data of individual plants and leaves. This is because in order to understand how plants are behaving, and changing, over large areas we must first link these remote sensing techniques to measured plant processes at the leaf scale. Here’s an overview of some of our instruments, and what we use them for…
Chlorophyll fluorescence – QE Pro spectrometer
The QE Pro-FL, made by Ocean Optics Ltd, is a spectrometer with a very high spectral resolution that is also designed for low light levels, making it ideal for measuring chlorophyll fluorescence. Solar-induced fluorescence is a passive technique that measures the light emitted by the leaf in narrow oxygen absorption bands O2-B (687 nm) and O2-A (761 nm). Fluorescence competes for the same absorbed light as photosynthesis and has been reported to be the most direct proxy for photosynthesis measurable using remote sensing techniques.
Photo credits: Cheryl Rogers
Hyperspectral reflectance – Spectral Evolution PSR+ 3500 spectrometer
Photo credits: Holly Croft and www.fsf.nerc.ac.uk
The PSR+ 3500 is a hyperspectral spectrometer, capable of measuring reflectance in visible to shortwave infrared wavelengths from 350-2500 nm, and with the added bonus of being lightweight and thoughtfully designed for fieldwork. Reflectance measurements enable us to distinguish between different vegetation types, and other ground materials, according to their distinct spectral signatures. Crucially, we can also calculate the quantity of some biochemical and physical constituents of leaves according to the position and depth of known absorption features.
Source: (Left) Huete (2004) Remote Sensing for Environmental Monitoring. https://doi.org/10.1016/B978-0-12-064477-3.X5000-0 and (Right) Croft and Chen (2018) Leaf pigment content. In: Liang (Ed) Comprehensive Remote Sensing.
Leaf photosynthesis – LI-6400 portable gas-exchange system
The LI-6400 measures the fluxes of carbon dioxide and water between a leaf and the air within a sealed chamber that are used to calculate leaf photosynthesis. The light, humidity, temperature and CO2 concentrations are carefully controlled, making it possible to conduct measurements under ambient conditions or under varying light or CO2 to reveal information about the underlying leaf biochemical or physiological characteristics.
Photo credits: Cheryl Rogers
Aerial videos/photos – DJI Mavic 2 Pro drone
We brought along a DJI Mavic 2 Pro equipped with a Hasselblad camera (20-megapixel photographs and 4K videos) to take aerial videos and images of our different arctic field sites. The Mavic 2 is very light and portable, making it great for fieldwork.
Reflectance images – Micasense RedEdge imaging sensor (and Kite)
The Micasense RedEdge is a small, lightweight sensor (180 g, 9.4 cm x 6.3 cm x 4.6 cm), which is small enough to mount on a drone or other airborne platform. In this case we are using a kite because it avoids battery-power issues, it’s low-cost and can provide a large dataset over a small area. The sensor measures reflectance in 5 wavebands (blue, green, red, red-edge, and near infra-red), which are particularly suitable for vegetation studies.
Thanks to the the NERC Field Spectroscopy Facility (FSF) for supporting the field campaign and for loaning us the Micasense RedEdge sensor and kite, Spectral Evolution PSR+ 3500 spectrometer and QE Pro spectrometer. The FSF operates an instrument pool that loans out state-of-the-art instruments based on a successful, peer-reviewed application. It is a unique and wonderful resource, run by knowledgeable and helpful people, and makes a huge contribution remote sensing science in the UK.