Towards mapping the diversity of canopy structure from space with GEDI

Plant biodiversity supports life on Earth and provides a range of important ecosystem services, but is 11 under severe pressure by global change. Structural diversity plays a crucial role for carbon, water and energy 12 cycles and animal habitats. However, it is very difficult to map and monitor over large areas, limiting our ability 13 to assess the status of biodiversity and predict change. NASA’s Global Ecosystem Dynamics Investigation (GEDI) 14 provides a new opportunity to measure 3D plant canopy structure of the world’s temperate, Mediterranean and 15 tropical ecosystems, but its potential to map structural diversity is not yet tested. Here, we use wall-to-wall airborne 16 laser scanning (ALS) to simulate GEDI data (GEDIsim) over 7380 km2 in the southern Sierra Nevada mountains in 17 California, and evaluate how well GEDI’s sampling scheme captures patterns of structural diversity. We evaluate 18 functional richness and functional beta diversity in a biodiversity hot spot. GEDIsim performed well for trait 19 retrievals (r2 = 0.68) and functional richness mapping (r2 = 0.75) compared to ALS retrievals, despite lower 20 correlations in complex terrain with steep slopes. Functional richness patterns were strongly associated with soil 21 organic carbon stocks and density as well as variables related to water availability, and could be appropriately 22 mapped by GEDIsim with and without cloud cover. Functional beta diversity was more strongly related to local 23 changes in topography and more challenging to map, especially with decreasing sampling density. The reduced 24 number of GEDIsim shots when simulating cloud cover lead to a strong overestimation of beta diversity and a 25 reduction of r2 from 0.64 to 0.40 compared to ALS. The ability to map functional richness has been demonstrated 26 with potential application at continental scales that could be transformative for our understanding of large-scale 27 patterns of plant canopy structure, diversity and potential links to animal diversity, movement and habitats.