Towards an operational root disease mapping methodology through lidar integrated imaging spectroscopy

Date

2011-10-17

Authors

Quinn, Geoffrey

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Abstract

Root disease is a serious concern for the softwood timber industry. This thesis reports on the development of a root disease detection procedure that applies lidar data integrated with imaging spectrometer data. Photosynthetic pigments are frequently cited as one of the most responsive indicators of vegetation stress. This study estimated pigment content from needle and canopy reflectance and characterized the sensitivity of these pigments to a fungal-mediated stress. Samples were collected from the Greater Victoria Watershed District on Vancouver Island, BC, Canada. Lab reflectance measurements were made and pigments were extracted. Reflectance spectra were transformed into derivative spectra and a continuum removal band depth analysis was conducted. Reflectance metrics were generated and used in modeling pigment content. Chlorophyll-a was found to be significantly affected by the disease in the needle level portion of this study. The predictive power of reflectance attributes were assessed and yielded strong coefficients of determination (R2>0.80). Samples exhibiting stress responses affected by root disease were discriminated. It was determined that younger trees were more severely affected by the root pathogen than mature colonized trees. In the canopy level component of the study, chlorophyll-a was estimated through the application of partial least squares regression and achieved an R2 value of 0.82. Continuum removal metrics, which proved to be good estimators at the needle level, were found to be insufficient at the canopy level. Through the use of hyperspectral forest chemistry products, potential root disease sites can be identified.

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Keywords

roots (botany), diseases, Vancouver Island, B.C.

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