Analysis of peatland carbon dynamics using combined optical and microwave satellite data

This project aims to develop remote sensing schemes for examining the resilience of restored peatlands to drought conditions, particularly of different peatland microforms, through the plant photosynthetic response to drought and rewetting.

Peatlands are a key component of the terrestrial carbon cycle. They sequester large amounts of carbon from the atmosphere. Peat-forming plants, and especially bryophytes such as Sphagnum mosses, are well adapted to this wet environment but suffer disproportionally in dry conditions. Many peatlands in the British Isles have been subject to deleterious management schemes, including drainage, overgrazing, planting for commercial forestry, and burning. Although large-scale restoration efforts have now been implemented, it is often challenging to completely restore the hydrological characteristics of such sites. This leaves them vulnerable to drought periods, during which markedly negative effects on photosynthesis of peatland vegetation, and ultimately carbon emissions, can be observed.

The number of Earth Observation satellites available to study peatlands has risen in the past few years with the advent of the Sentinel-1 and Sentinel-2 missions. The Sentinel-1 satellites carry synthetic aperture radar (SAR) instruments which are sensitive to soil and plant moisture and, critically, are not affected by cloud cover which can often otherwise restrict optical/IR measurements of peatland areas. The Sentinel-2 satellites carry optical instruments that are sensitive to the visible and near infra-red parts of the electromagnetic spectrum. This makes them ideal for monitoring plant health. In future, we will also have direct observations of photosynthesis from the European Space Agency's FLEX Earth Explorer mission (planned launch 2022), which measures Solar Induced Fluorescence (SIF) from plants.

The student will investigate the synergistic exploitation of current and future satellite microwave radar, visible, infrared, and SIF platforms for the remote sensing of drought responses of peatlands and test the feasibility of remotely monitoring peatland resilience on a landscape scale. The work falls into three components:
1) Laboratory-based study of the drying and rewetting response of different peatland microforms. We will house these experiments on a lysimeter and take regular measurements with UoR's ground-based radar system configured to match Sentinel-1 measurements. Optical measurements to simulate Sentinel-2 will be taken alongside the SAR observations. Together these will be used to calibrate a joint SAR-optical model of drying and rewetting responses
2) Field-based studies of optical and SIF measurements. The student will conduct a field campaign during year 1-2 to monitor restored and non-restored sites with hand-held optical instruments. These data, alongside in-situ soil moisture and gross primary production data (JHI long term eddy covariance monitoring datasets) will allow us to test models devolved in (1). The SIF data will be used to explore the additional benefit of missions such as FLEX.
3) Examine the 2018 drought, which provides an exceptional opportunity to understand the remote sensing signals of peatland water stress. The Sentinel-1 and 2 data for 2018 will be extracted for the Forsinard flows and the impact of the drought of that year on the peatlands will be explored based on the relationships built in (1) and (2).