The concept for a new multi-spectral canopy LIDAR (MSCL) instrument was tested by simulating return waveforms using models providing tree structure (TREEGROW) and leaf
reflectance (PROSPECT). The proposed instrument will take measurements at four different wavelengths, which were chosen according to physiological processes altering leaf reflectance.
The modelling was used to assess both the structural and physiological information content such a device could provide, especially if the normally structure-dominated return waveform would pick up small changes in reflectance at the leaf level. Multi-spectral waveforms were simulated for models of single Scots pine trees of different ages and at different stages of the growing season. It was shown that the LIDAR waveforms would not only capture the tree height information, but as would also pick up the seasonal and vertical variation of NDVI computed from two of the four
MSCL wavelengths inside the tree canopy. It could be demonstrated that a new multi-wavelength LIDAR predictor variable could significantly improve the retrieval accuracy of photosynthetically active biomass opposed to using a single wavelength LIDAR alone. It remains unclear, however, if these findings would persist for forest stands; thus such experiments simulating more complex scenarios will be the next task in this modelling framework.