Improving Forest Carbon Uptake Estimates Using High-resolution Airborne Remote Sensing Data

The objective of this project was to collect detailed information on topography and structure of vegetation surrounding three well-established flux towers. Within the EU10-01 project, the NERC Airborne Research and Survey Facility (ARSF) flew surveys over three sites in the Netherlands (2010), in Germany (2010), and in Sweden (2010 / 2011), collecting LiDAR, hyperspectral, and digital aerial photography data at high spatial density. Ecological field data and carbon dioxide and water vapour exchange fluxes were collected at the same time at all three sites. Two Leica GPS Systems (provided by the NERC Geophysical Equipment Facility, GEF) were deployed to these sites in support of the airborne and ground based surveys, providing highly essential GPS base station and rover data during the time of the data collection. Further, the NERC Field Spectroscopy Facility (FSF) provided equipment for calibration of the airborne hyperspectral imagery. The above data has been processed to derive maps of digital elevation, tree height, canopy height, fractional cover of vegetation, and leaf area index. Background Flux-tower measurements are increasingly used to quantify the exchange of carbon dioxide (CO2) and water vapour (H2O) between the Earth’s surface and the atmosphere. Uncertainty in the source area (footprint) of these measurements leads to large errors in the calculation of the CO2 and H2O budgets; at present only 60-80% of the signal measured by flux towers can be accounted for. Detailed information on topography and structure of vegetation surrounding flux towers allows for reducing these errors. For this project, three well-established European flux towers have been selected. These longterm flux-tower sites represent three typical European forest biomes and are located in Germany (Tharandt), the Netherlands (Loobos), and in Sweden (Norunda); see Figures 1 and 2 and Table 1 for survey location and maps. The dataset collected within this project combines spaceborne and airborne LiDAR, hyperspectral imagery, aerial spectral photography, historic and coincident eddy-covariance measurements from the three flux towers, and ecological data from the tower areas. A method for reducing uncertainty in the upscaling of greenhouse gas fluxes to a regional or even global scale is improved and evaluated based on this dataset. The two GEF GPS systems were used to provide static real-time mode base station data for the airborne survey and to position the ground-based calibration measurements (flux tower, ecological measurements) with high accuracy relative to the airborne data. NERC Geophysical Equipment Facility View more reports on our website at http://gef.nerc.ac.uk/reports.php