Dieback classification modelling using high-resolution digital multispectral imagery and in situ assessments of crown condition

Abstract

<p>Quantifying dieback in forests is useful for land managers and decision makersseeking to explain spatial disturbances and understand the cyclic nature of for-est health. Crown condition is assessed as reference to dieback in terms of thedensity, transparency, extent and in-crown distribution of foliage. At 20 sites inthe Yalgorup National Park, Western Australia, a total of 80 <i>Eucalyptus gompho-cephala</i> crowns were assessed both <i>in situ</i> (2008) and using two acquisitions (2008and 2010) of airborne imagery. Each tree was assessed using four crown-condition indices: Crown Density, Foliage Transparency, the Crown Dieback Ratio and Epicormic Index combined into a single index called the Total Crown Health Index(TCHI). The airborne imagery is like value calibrated then classified and modelledusing in situ canopy condition assessments resulting in a quantification of crown-condition change over time. Comparison of Normalized Difference VegetationIndex (NDVI), Soil-Adjusted Vegetation Index (SAVI) and a novel Red-EdgeExtrema Index (REEI) suggests that the latter is more suited to classificationapplications of this type.</p>