Generality of relationships between leaf pigment contents and spectral vegetation indices in Mallorca (Spain)

Lea Hallik,Magdalena Tomás,Andres Kuusk,Taras Kazantsev,Ülo Niinemets,Jeroni Galmés

doi:10.1007/s10113-017-1202-9

Abstract

Vegetation indices are calculated from reflectance data of discrete spectral bands. The reflectance signal in the visible spectral range is dominated by the optical properties of photosynthetic pigments in plant leaves. Numerous spectral indices have been proposed for the estimation of leaf pigment contents, but the efficacy of different indices for prediction of pigment content and composition for species-rich communities is unknown. Assessing the ability of different vegetation indices to predict leaf pigment content we identify the most suitable spectral indices from an experimental dataset consisting of field-grown high light exposed leaves of 33 angiosperm species collected in two sites in Mallorca (Spain) with contrasting leaf anatomy and pigment composition. Leaf-level reflectance spectra were recorded over the wavelength range of 400 – 900 nm and contents of chlorophyll a, chlorophyll b, total carotenoids, and anthocyanins were measured in 33 species from different plant functional types, covering a wide range of leaf structures and pigment content, five-fold to more than 10-fold for different traits. The best spectral region for estimation of leaf total chlorophyll content with least interference from carotenoids and anthocyanins was the beginning of near-infrared plateau well beyond 700 nm. Leaves of parallel-veined monocots and pinnate-veined dicots had different relationships between vegetation indices and pigments. We suggest that the nature and role of “far-red” chlorophylls which absorb light at longer wavelengths than 700 nm constitute a promising target for future remote sensing studies.

Highlights

The life on Earth primarily relies on sunlight energy captured by plant pigments to drive the process of photosynthesis
Pigment stoichiometry can quickly acclimate to environmental conditions
Our dataset contained only high-light-grown leaves and the variability in pigment composition originates from species-specific differences not from the acclimation to Different leaf structures as sclereids, leaf bundle sheath extensions, cell walls, and mesophyll cells have been described as traits affecting the spectral properties of leaves (Poulson and Vogelmann 1990; Smith et al 1997; Nikolopoulos et al 2002)

Summary

Introduction

The life on Earth primarily relies on sunlight energy captured by plant pigments to drive the process of photosynthesis. Proteins coordinate the orientation and distance of pigments relative to each other and, play a crucial role determining the absorption and emission spectra of chlorophylls and carotenoids (Fowler et al 1992; Bassi and Caffarri 2000). Even as small changes as single amino acid substitutions in a pigment-binding protein can have notable effects on spectral properties of pigmentprotein complexes (Morosinotto et al 2003). Presence of multiple absorption forms of pigments due to differences in protein structures of pigment-binding complexes allows leaves to capture light effectively over a wide spectral region and determines the spectral properties of the whole leaf (Wientjes et al 2012). Despite of the difficulties in purification of pigment-protein complexes, significant advancements have been made in biochemical and spectroscopic characterization of components of PSI and PSII (Caffarri et al 2009; Wientjes and Croce 2011) and their acclimation to growth-light spectrum (Hogewoning et al 2012)

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