DOI: 10.5061/dryad.mw6m9063x
title: Data from: Reflections of stress: Ozone damage in broadleaf saplings can be identified from hyperspectral leaf reflectance

description: Tropospheric ozone causes widespread damage to vegetation, however,
 monitoring of ozone-induced damage is usually reliant on manual leaf
 inspection. Reflectance spectroscopy of vegetation can identify and detect
 unique spectral signatures of different abiotic and biotic stressors. In
 this study, we tested the use of hyperspectral leaf reflectance to detect
 ozone stress in alder, beech, birch, crab apple, and oak saplings exposed
 to five different ozone regimes (ranging from daily target maxima of 30ppb
 ozone to 110ppb). Hyperspectral reflectance varied significantly between
 ozone treatments, both in whole spectra analysis and when simplified to
 representative components. Ozone damage had a multivariate impact on leaf
 reflectance, underpinned by changes in pigment balance, water content, and
 structural composition. Vegetation indices derived from reflectance which
 characterised the visible green peak were able to differentiate between
 ozone treatments. Iterative normalised difference spectral indices across
 the hyperspectral wavelength range were correlated to visual damage scores
 to identify significant wavelengths for ozone damage detection. We propose
 a new Chronic Ozone Damage Index (COzDI), which characterises the
 reflectance peak in the shortwave infrared region and is highly correlated
 to ozone damage. These results pioneer hyperspectral reflectance as a
 high-throughput method of ozone damage detection in a range of common
 broadleaf species.
description: This experiment took place at the UK Centre for Ecology &
 Hydrology's air pollution facility at Abergwyngregyn, North Wales
 (53.2◦N, 4.0◦W). Ozone treatment was delivered in solardomes, dome-shaped
 glasshouses of 3 m diameter and 2.1 m height. From June to October 2022,
 alder, beech, birch, oak, and crab apple saplings were grown within the
 ozone treatment solardomes. Each month hyperspectral leaf reflectance
 measurements were taken.  Reflectance spectra of the adaxial leaf surface
 from 350-2500nm were collected using an HR-1024i with leaf clip, Spectra
 Vista Corp, USA including an active light source.  The
 spectrometer was referenced using the incorporated leaf clip reflective
 standard every 5 minutes during measurements. Dark signal baseline
 correction was applied by the HR-1024i automatically, a dark spectrum was
 taken before each reflectance measurement. Once per month during ozone
 treatment, reflectance spectra were taken of three leaves from three
 replicates of each species per ozone treatment. The three leaves were
 chosen as one from each third of the vertical span of the sapling's
 leaf cover, including young, mature, sun, and shaded leaves.
 Reflectance spectra were imported and processed as a spectral
 library in Python 3 using the SpecDAL package. The overlapping regions of
 the three component spectrometers in the HR-1024i were stitched.
 Reflectance measurements were interpolated to correspond to 1nm interval
 wavelengths. Absolute reflectance was derived from the relative
 reflectance by multiplying by the known reflectance of the reference
 panel. Noisy regions caused by water vapour absorption at 1350-1460nm and
 1790-1970nm were smoothed using a Savitsky-Golay Filter. Spectra were
 grouped by attributes including species, ozone treatment, and date of
 measurement.
description: # Hyperspectral Leaf Reflectance Library of Ozone Exposed Saplings
 Hyperspectral leaf
 reflectance spectral library recorded from broadleaf saplings grown under
 varying ozone concentrations from June-October 2022. ## Description of the
 data and file structure The hyperspectral library is stored in CSV file
 format. Each column is an individual reflectance spectra, labelled in row
 1 according to the species, month of measurement, ozone treatment and
 sapling number. Each row corresponds the intensity values for a particular
 wavelength, labelled in column 1, ranging from 350-2500nm. The spectra are
 labelled according to the following protocol:
 [[MONTH]_[SPECIES]_[TREATMENT]_[SAPLING NUMBER].[REPEAT NUMBER] Where: A =
 Alder B = Birch C = Crab apple F = Beech Q = Oak OZ_1 = Ozone treatment
 with daily target maximum 30ppb OZ_2 = Ozone treatment with daily target
 maximum 50ppb OZ_3 = Ozone treatment with daily target maximum 65ppb OZ_4
 = Ozone treatment with daily target maximum 80ppb OZ_5 = Ozone treatment
 with daily target maximum 110ppb HT_M = Heated ozone treatment with daily
 target maximum 30ppb HT_H = Heated ozone treatment with daily target
 maximum 110ppb e.g. OCT_B_OZ_4_10.0002 is the label for the second repeat
 reflectance spectra taken in October from Birch sapling number 10 in ozone
 treatment 4 (daily target maximum 80ppb)