Phylogenetic Structure of Foliar Spectral Traits in Tropical Forest Canopies

Kelly Mcmanus,Kyle Dexter,Christopher Field,W Kress,Gregory Asner,Roberta Martin

doi:10.3390/rs8030196

Abstract

The Spectranomics approach to tropical forest remote sensing has established a link between foliar reflectance spectra and the phylogenetic composition of tropical canopy tree communities vis-à-vis the taxonomic organization of biochemical trait variation. However, a direct relationship between phylogenetic affiliation and foliar reflectance spectra of species has not been established. We sought to develop this relationship by quantifying the extent to which underlying patterns of phylogenetic structure drive interspecific variation among foliar reflectance spectra within three Neotropical canopy tree communities with varying levels of soil fertility. We interpreted the resulting spectral patterns of phylogenetic signal in the context of foliar biochemical traits that may contribute to the spectral-phylogenetic link. We utilized a multi-model ensemble to elucidate trait-spectral relationships, and quantified phylogenetic signal for spectral wavelengths and traits using Pagel’s lambda statistic. Foliar reflectance spectra showed evidence of phylogenetic influence primarily within the visible and shortwave infrared spectral regions. These regions were also selected by the multi-model ensemble as those most important to the quantitative prediction of several foliar biochemical traits. Patterns of phylogenetic organization of spectra and traits varied across sites and with soil fertility, indicative of the complex interactions between the environmental and phylogenetic controls underlying patterns of biodiversity.

Highlights

Advances in ecological remote sensing over recent decades have contributed substantial new insights into patterns and processes of biophysical and biochemical variation in species-rich tropical forests
We investigate the relationship between foliar reflectance spectra and phylogenetic structure by (1) examining the relationships between spectra and a suite of nine biochemical traits that relate to a wide range of leaf functions and which are known to be expressed in leaf reflectance spectra; and (2) directly quantifying the phylogenetic signal of these biochemical traits
Spectral regions exhibiting significant phylogenetic signal broadly overlapped with the spectral regions selected by the multi-model ensemble as those most important to the quantitative prediction of the nine foliar traits measured in this study (Figure 2)

Summary

Introduction

Advances in ecological remote sensing over recent decades have contributed substantial new insights into patterns and processes of biophysical and biochemical variation in species-rich tropical forests. An exception is the work of Asner and Martin (2009) [12], which quantified the taxonomic and environmental components of trait variation across a gradient of soil fertility in a lowland Amazonian forest, using a hierarchical ANOVA procedure to partition taxonomic variance of biochemical traits into family, genus-within-family, and species-within-genus components. While this approach quantifies the entire pattern in phylogenetic relatedness in a community, it does not allow for variance in the distance between taxa at the same taxonomic rank. Explicit phylogenetic analyses using phylogenies derived from DNA sequence data may resolve the role of relatedness in determining patterns of trait variation, among species and genera [22]

Methods

Results

Discussion

Conclusion