Michael Schlund; Margarita Huesca Martinez
Role of Forests in Climate Change Mitigation
There are several sites for which fieldwork is possible, both inside and outside the Netherlands.
The monitoring of forests is important due to their function in the global carbon cycle for carbon storage when growing or undisturbed, and as a source of carbon when disturbed. At the same time, forests should also maintain their other ecosystem services like biodiversity and material cycles. The forest canopy height can be estimated with different remote sensing techniques, where LiDAR and high-frequency SAR data seems particularly useful to estimate forest canopy height. The forest canopy height is assumed to be a proxy for other forest structure metrics (e.g. biomass) and is important for the assessment of heterogeneity and biodiversity of a forest. However, airborne LiDAR sensors have normally a small spatial coverage and the data are relatively expensive compared to spaceborne data resulting in limited potential for applications on large scales and change estimations. In contrast, the potential of TanDEM-X data to estimate forest canopy height with empirical and semi-empirical models was demonstrated in a few case studies in the past (Schlund et al. 2019). The established models can be also applied on data acquired at a different time to estimate the change of forest canopy height and its biomass (Knapp et al. 2018). This study will be part of a developing research field, where it will further assess the potential of TanDEM-X InSAR data to estimate forest canopy height in different forest types. The study could further analyse the change of forest canopy height estimated with TanDEM-X depending on data availability. The estimated forest canopy height can be further used as proxy for aboveground biomass and other structural metrics, which could be linked to biodiversity. Possible sites include forests in 1) Overijsel, the Netherlands, 2) national forest park(s) in Germany and/or 3) tropical forest of Jambi, Indonesia.
The objectives are flexible, and depend on the precise case study chosen. Below a few basic example objectives are listed.
- To estimate forest canopy height with TanDEM-X InSAR data with different techniques;
- To estimate the change of forest canopy height with at least bi-temporal TanDEM-X data;
- To evaluate the accuracy of such estimates in relation to field and LiDAR data;
- To link the forest canopy height with other forest structure metrics (e.g. biomass) and/or biodiversity.
The student will work with interferometric synthetic aperture radar (InSAR) data acquired from TanDEM-X. Interferometric height and other metrics (e.g. volume coherence) will be extracted. Simple models will be further used together with reference data from in situ and/or LiDAR data to estimate forest canopy height. The student could subsequently link such retrievals with aboveground biomass and/or biodiversity.
For most case studies, good programming experience is a prerequisite.
Schlund, M, P Magdon, B Eaton, C Aumann, and S Erasmi (2019). Canopy height estimation with TanDEM-X in temperate and boreal forests. Int J Appl Earth Obs Geoinformation 82.
Knapp, N, A Huth, F Kugler, K Papathanassiou, R Condit, SP Hubbell, and R Fischer (2018). Model-assisted estimation of tropical forest biomass change: a comparison of approaches. Rem. Sens. 10 (5).