Fundamental drivers of plant spectral diversity

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Plant spectral diversity how leaves of plant species differentially interact with solar radiation is a highly promising but still largely unknown facet of biodiversity. Plant spectral diversity is of high interest because it can be directly remotely sensed, and because it is a powerful integrator of plant phylogenetic and functional diversity. As a result, a new field called “spectranomics” is revolutionizing how we acquire high-resolution biodiversity data over large regions. However, we still know little about the basic drivers of leaf spectral variation across species and environments. The overall objective of my research program is to determine the fundamental drivers of leaf spectral variation within and among plant species, communities, and across soil fertility gradients. The proposed research program builds from my previous Discovery Grant in trait-based plant ecology along natural soil fertility gradients, and develops exciting new research directions about spectral diversity and its linkages with phylogenetic and functional diversity. The central hypothesis is that leaf spectral variation is primarily determined by phylogeny, and secondarily by the environment. The research program is organised around three shorter-term objectives. In the first objective, I will identify fundamental axes of leaf spectral variation among species. Here, I will test the hypothesis that spectral variation is organised along three major axes expressing: (1) the leaf economics spectrum, (2) a trade-off between chemical and structural defences, and (3) a leaf hydraulics spectrum. To do so, I will conduct a large-scale field survey of spectra and traits for a large number of canopy plant species spread across broad edaphic and climatic gradients, using our network of soil chronosequences in Australia. My second objective is to quantify the degree of spectral plasticity within plant species. Specifically, I will test the hypothesis that species with broader edaphic niches show higher spectral plasticity. To do so, I will use a combination of field observations along long-term soil chronosequences and common garden experiments spanning large soil fertility gradients to provide the most comprehensive and rigorous quantification of leaf spectral plasticity to date. Finally, my third objective is to determine the drivers of leaf spectral diversity within and among communities across fertility gradients. In particular, I will test the hypothesis that community-level shifts in spectral diversity across soil fertility gradients express changes in plant taxonomic and functional diversity. This research will be conducted along the Jurien Bay soil chronosequence in Australia, which is one of the strongest natural soil fertility gradients ever described. By unravelling the fundamental drivers of leaf spectral variation across plant species and environments, my research will pave the way for a future global biodiversity observatory informed by spectranomics.