Forests cover 4.1 billion hectares of the Earth’s land surface, 42% of which is found tropical latitudes. The height of forest canopies plays an important role in shaping primary productivity, intra- and inter-specific competition for light, as well as ground and surface water inputs. Canopy height can vary with topography, tree species richness, rainfall and temperature, but the relative importance of these factors in shaping this key property of forests is unclear. This study explores the drivers of canopy height across the Americas using several continental-scale datasets: the Geoscience Laser Altimeter System, a space-borne LiDAR system, plant species richness from the Botanical Information and Ecology Network (BIEN) and global climatic and elevation data. While previous studies often focus on assessing how canopy height relates to single predictor variables, we also included multivariate models in our analyses.
Species richness was positively but weakly related to canopy height in a bivariate regression but surprisingly, it was not selected in the multivariate model. Instead, the multivariate model was comprised of annual temperature, precipitation seasonality, precipitation in the wettest month, elevation and mean diurnal range in temperature, which were all significant predictors. Precipitation seasonality had the strongest influence, while precipitation in the wettest month and the mean diurnal range in temperature were also important. These results clarify our understanding of the drivers of canopy height, which influences carbon sequestration, primary productivity and community structure across the Americas.