Abstract
This study explores ICESat/GLAS waveform data in Thuringian Forest, a low mountain range located in central Germany. Lidar remote sensing has been proven to directly derive tree height as a key variable of forest structure. The GLAS signal is, however, very sensitive to surface topography because of the large footprint size. This study therefore focuses on forests in a mountainous area to assess the potential of GLAS data to derive terrain elevation and tree height. The work enhances the empirical knowledge about the interaction between GLAS waveform and landscape structure regarding a special temperate forest site with a complex terrain. An algorithm to retrieve tree height directly from GLA01 waveform data is proposed and compared to an approach using GLA14 Gaussian parameters. The results revealed that GLAS height estimates were accurate for areas with a slope up to 10° whereas waveforms of areas above 15° were problematic. Slopes between 10–15° have been found to be a critical crossover. Further, different waveform shape types and landscape structure classes were developed as a new possibility to explore the waveform in its whole structure. Based on the detailed analysis of some waveform examples, it could be demonstrated that the waveform shape can be regarded as a product of the complex interaction between surface and canopy structure. Consequently, there is a great variety of waveform shapes which in turn considerably hampers GLAS tree height extraction in areas with steep slopes and complex forest conditions.
Highlights
Forests are an important natural resource and play a major role in the global carbon cycle
The two GLA01 and GLA14 terrain elevations were compared to the mean airborne laser scanning (ALS) Digital Terrain Model (DTM) elevation of each footprint
This paper demonstrated the potential of estimating terrain elevation and tree height using
Summary
Forests are an important natural resource and play a major role in the global carbon cycle. Accurate and repeated forest mapping at local, regional and global scales is required for a better understanding of the global climate change and for the development of sustainable forest management strategies. Tree biomass is a key to a forest ecosystem’s function and its role for the carbon fluxes between biosphere, atmosphere and oceans. Plants store the greenhouse gas carbon dioxide in their above and belowground biomass. Be considered as one of the most significant terrestrial carbon sinks [1,2]. Biomass estimations refer to the horizontal and vertical forest structure
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