A Protocol for Standardizing Measurements and Enabling Global Harmonization of Herbarium Leaf Reflectance Spectra

Dawson M White , Flávia Machado Durgante, Matthew Austin, J. Antonio Guzmán Q., Jonathan A Kennedy, Cornelius Onyedikachi Nichodemus, Natalie Iwanycki Ahlstrand, Chris Baraloto, Billur Bektaş, Khalil Boughalmi, Warren Cardinal-McTeague, Thomas L.P. Couvreur, Riley P Fortier, Ryan S Fuller, Olwen M. Grace, Rykkar Jackson, Kevin Karbstein, Shan Kothari, Aaron Lee, Jéssica Lira Viana, Elizabeth Martinez-Victoria, Jose Eduardo Meireles, Thomas H Murphy, Carlos Rodriguez Vaz, Daniel Spalink, Hanna Tuomisto, Caroline da Cruz Vasconcelos , Jeannine Cavender-Bares 

Reflectance spectroscopy offers a powerful approach to integrate high-

throughput phenotypic data from herbarium specimens into the digital landscapes of ecology,

evolution, and systematics. Spectral digitization complements specimen metadata capture and

photographic imaging by generating high-dimensional optical data from herbarium tissues that

encode information about plant chemistry and structure. Because inconsistencies in

instrumentation and measurement practices can increase noise and limit dataset compatibility,

the International Herbarium Spectral Digitization Working Group (IHerbSpec) has published the

Protocol for Spectral Digitization of Herbarium Specimens, currently in version 1.3, as an open

resource that will continue to evolve through community use and collaboration

(https://iherbspec.github.io/protocol). The protocol defines a stepwise measurement workflow,

standardized filename conventions, structured metadata tables with controlled vocabularies, and

guidance on tissue selection, materials, and instrumentation quality control to support spectral

datasets that are interoperable across projects and reusable through well-documented metadata.

By embedding standardized practices at the point of data collection, it provides a scalable

foundation for data synthesis and new quantitative insights into plant diversity across taxonomic,

geographic, and temporal scales.