Exploring patterns of fine root morphological, chemical, and anatomical traits of 12 tree species from visible–near-infrared spectral reflectance

Abstract

Visible and near-infrared spectral reflectance can be used to determine the chemical composition of soil and plant organs. However, previous research has not used this for fresh fine root systems of tree species. We aimed to explore the predictive ability of spectral reflectance relationships among fine-root morphological, anatomical, and chemical traits for 12 tree species in a temperate forest in Japan. Intact fresh systems of fine root were imaged at 478–978 nm wavelengths (153 bands, 3.6 nm interval). Relationships between spectral reflectance and specific root length, root tissue density, branching intensity, stele/cortex ratio, and Ca concentration were analyzed at each spectral band. Reflectance peaked at around 920 nm across all species; however, reflectance magnitude at spectral regions of blue (478 nm), green (546 nm), red (648 nm), and near-infrared (847 nm) significantly differed among species. All variables measuring traits were significantly correlated with spectral reflectance only at specific wavelengths, but the strength of the correlation differed among wavelengths. Spectral reflectance in visible–near-infrared regions for fresh intact root systems can evaluate the species-differences in fine root traits, and can predict fine root traits across species. Our findings facilitate a general assessment of root traits across tree species and will allow more accurate estimation of fine root functions.