Sources of Canopy Chemical and Spectral Diversity in Lowland Bornean Forest

Sources of variation among the chemical and spectral properties of tropical forest canopies are poorly understood, yet chemical traits reveal potential ecosystem and phylogenetic controls, and spectral linkages to chemical traits are needed for remote sensing of functional and biological diversity. We analyzed 21 leaf traits in 395 fully sunlit canopies, representing 232 species and multiple growth forms, in a lowland mixed dipterocarp forest of Sarawak, Malaysia. Leaf traits related to light capture and growth (for example, photosynthetic pigments, nutrients) were up to 55% lower, and defense traits (for example, phenols, lignin) were 15-40% higher, in the dominant family Dipterocarpaceae and in its genus Shorea, as compared to all other canopy species. The chemical variation within Dipterocarpaceae and Shorea was equivalent to that of all other canopy species combined, highlighting the role that a single phylogenetic branch can play in creating canopy chemical diversity. Seventeen of 21 traits had more than 50% of their variation explained by taxonomic grouping, and at least 16 traits show a connection to remotely sensed spectroscopic signatures (RMSE < 15%). It is through these chemical-to-spectral linkages that studies of functional and biological diversity interactions become possible at larger spatial scales, thereby improving our understanding of the role of species in tropical forest ecosystem dynamics.