Canopy phylogenetic chemical and spectral assembly in a lowland Amazonian forest
Asner GP; Martin RE
Canopy chemistry and spectroscopy offer insight into community assembly and ecosystem processes in high-diversity tropical forests but phylogenetic and envi- ronmental factors controlling chemical traits underpinning spectral signatures remain poorly understood.\nâ€¢ We measured 21 leaf chemical traits and spectroscopic signatures of 594 canopy individuals on high-fertility Inceptisols and low-fertility Ultisols in a lowland Amazonian forest. The spectranomics approach which explicitly connects phylo- genetic chemical and spectral patterns in tropical canopies provided the basis for analysis.\nâ€¢ Intracrown and intraspecific variation in chemical traits varied from 1.4 to 36.7% (median 9.3%) depending upon the chemical constituent. Principal com- ponents analysis showed that 14 orthogonal combinations were required to explain 95% of the variation among 21 traits indicating the high dimensionality of canopy chemical signatures among taxa. Inceptisols and lianas were associated with high leaf nutrient concentrations and low concentrations of defense com- pounds. Independent of soils or plant habit an average 70% (maximum 89%) of chemical trait variation was explained by taxonomy. At least 10 traits were quanti- tatively linked to remotely sensed signatures which provided highly accurate species classification.\nâ€¢ The results suggest that taxa found on fertile soils carry chemical portfolios with a deep evolutionary history whereas taxa found on low-fertility soils have under- gone trait evolution at the species level. Spectranomics provides a new connection between remote sensing and community assembly theory in high-diversity tropical canopies.