Comparative assessment of single-tree and plot-based aboveground biomass estimations from airborne laser scanning point clouds
The topic is open and also suitable for GEM students in track 3 – GEM for Ecosystems & Natural Resources.
Suggested elective courses:
- Forest monitoring and carbon stock estimation with multi-source remote sensing in the context of climate change
The estimation of AGB and its changes is typically carried out using active remote sensing data such as laser scanning data due to their capability of penetrating the tree canopies, thus measuring the main biomass components (i.e., the tree trunks and branches). Established relationships between the tree components (diameter or height) are further used to estimate AGB. These can be measured in the field, but also with point clouds from laser scanning data. However, the detection of individual trees and the retrieval of their components can be a challenge. In contrast, comprehensive metrics summarizing the individual trees within an unit area (i.e., plot) can also be used to estimate the AGB. It could be that important information is neglected in such summarizing metrics. This suggests that the single-tree and plot-based AGB estimation have their strengths and weaknesses potentially propagating to different results and accuracies.
Accurate and spatially explicit quantification of carbon stocks are important to assess the impacts of the changes in the carbon cycle. Further, it supports the development of mechanisms to reduce carbon emissions, as e.g. in REDD+ (Reducing Emissions from Deforestation and Degradation). Aboveground biomass (AGB) is considered as a relevant proxy for the carbon stocks. The potential of laser scanning data to estimate AGB has long been recognized. The estimation can be based on the retrieval of metrics of individual trees from the laser scanning point cloud, which are used to estimate the AGB of individual trees. Finally, the individual trees have to be summed up to estimate the total AGB of a forest area. In contrast, the AGB can be also estimated on plot basis, where comprehensive metrics for a unit area (i.e., a plot) are calculated from the point cloud and used to estimate the AGB. The aim of this research is to use both techniques to estimate AGB and provide comparative information about their accuracies as well as strengths and weaknesses.
Campbell, M.J., Eastburn, J.F., Mistick, K.A., Smith, A.M. & Stovall, A.E.L. (2023) Mapping individual tree and plot-level biomass using airborne and mobile lidar in piñon-juniper woodlands. International Journal of Applied Earth Observation and Geoinformation 118
Coomes, D.A., Dalponte, M., Jucker, T., Asner, G.P., Banin, L.F., Burslem, D.F.R.P., Lewis, S.L., Nilus, R., Phillips, O.L., Phua, M.-H. & Qie, L. (2017). Area-based vs tree-centric approaches to mapping forest carbon in Southeast Asian forests from airborne laser scanning data. Remote Sensing of Environment 194, 77-88.
Jucker, T., Caspersen, J., Chave, J., et al. (2017). Allometric equations for integrating remote sensing imagery into forest monitoring programs. Global Change Biology, Volume 23, Issue 1, 177–190.