Characterizing eucalypt leaf phenology and stress with spectral analysis
Barry, KM and Corkrey, R and Stone, C and Mohammed, CL, Characterizing eucalypt leaf phenology and stress with spectral analysis, Innovations in Remote Sensing and Photogrammetry , Springer, Jones S, Reinke K (ed), Berlin Heidelberg, pp. 193-210. ISBN 978-3-540-88265-7 (2009) [Research Book Chapter]
Detection of stress with remote sensing in any vegetation type relies on
development of methods that highlight properties associated with stress which are
discernable from background variation, such as phenological changes. Therefore
the nature (and timing) of phenological foliar change needs to be systematically
compared to foliar stress symptoms with physical, biochemical and optical analyses.
Two such case studies with eucalypt species are presented here, including
Eucalyptus globulus and Eucalyptus pilularis. Studies with both eucalypt species
have shown that different leaf ages can be associated with alterations in pigments
and properties that are as pronounced as those occurring for well-developed stress
responses (potassium deficiency for E. globulus and low nutrient and cold exposure
in E. pilularis). Chlorophyll, carotenoid and anthocyanin content were analysed,
as well as specific leaf area and water content. Significant differences between leaf
ages were detected for many of these leaf pigments and properties, but the significant
differences between healthy and stressed leaves were usually of greater magnitude.
Only carotenoid content was not significantly different with leaf age for E. globulus,
but was significantly different with potassium-deficiency. This is a basis to further
investigate the potential of carotenoids to discern stressed leaves from phenological
changes. Preliminary data shown here provides a background for ongoing spectral
research on this theme for eucalyptus.