Spectral identification of ozone‐damaged pine needles

Abstract

Needles were collected from ponderosa and Jeffrey pine trees at three sites in the Sierra Nevada, and were assembled into 504 samples and grouped according to five dominant live needle conditions – green, winter fleck, sucking insect damage, scale insect damage, and ozone damage – and a random mixture. Reflectance and transmittance measurements of abaxial and adaxial surfaces were obtained at ca 0.3 nm spectral resolution from 400–800 nm, and binned to simulate Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) data. There were no significant differences in optical properties between the two surfaces. Ozone‐damaged needles were collected from Jeffrey pine trees at one site, and exhibited significantly different (family‐wise α = 0.01) reflectance and transmittance signatures – and significantly different signature slopes – at both spectral resolutions, from green and winter fleck needles from the same site. Ozone‐damaged needles had significantly different (family‐wise α = 0.01) abaxial surface reflectance and reflectance slope signatures from all other groups of needles, at both spectral resolutions. In comparison with three chlorophyll reflectance indices, a new red fall index (RFI) provides high classification accuracies for ozone‐damaged and non‐ozone‐damaged pine needles (overall acc. = 94%; κ = 59%). Thus, ozone‐damaged Jeffrey pine needles have a unique spectral signature in relation to dominant needle conditions of ponderosa and Jeffrey pine trees.

Acknowledgements

The authors greatly appreciate the support of everyone who made this project possible, especially Dr Dennis Baldocchi and his lab team at the University of California, Berkeley, who provided the equipment and guidance to measure the optical properties of pine needles. The authors are also grateful to Dr Tasios Melis and his talented plant biology lab team at the University of California, Berkeley, who provided the facility and guidance to carry out the biochemical analysis of pine needles. The authors also thank Sarah and Vincent Di Vittorio, Gary Bickel and Fernando Sedano for their assistance in collecting pine needles, and Annie Esperanza, the air quality specialist for Seqouia‐Kings Canyon National Park, for helping locate ozone‐damaged pine trees. The authors are grateful to Dr Dennis Baldocchi for reading the manuscript and providing insightful methodological and editorial feedback. Statistical tests were performed with the CLEAVE program developed by Timothy Herron.