Preliminary assessment of Phellinus weirii - Infected (laminated root rot)trees with high resolution CASI imagery

Root diseases caused by several endemic fungi are economically and ecologic ally important disturbance agents in the forests of western North America. Laminated root rot (Phellinus weirii) has particularly important impact in coastal Douglas-fir stands. Forest managers would like an economical survey procedure for detecting pockets of Phellinus weirii infected trees for the purpose of salvage, remedial activities and inventory. Aerial survey with multispectral imagers such as casi, coupled with automated detection of dam aged trees may provide a cost-effective survey method. Casi imagery in eight spectral bands has been corrected to an orthoimage an d radiometric corrections for the effects of illumination and view angle ap plied. Trees of varying levels of root rot symptoms were assessed in the fi eld and related to delineated trees on the imagery. Visual symptoms on the ground ranged from subtle crown shape and growth rate changes, through grad ual needle loss, to mortality. Chlorosis occurred on some trees. Preliminar y analysis, including classification and regression analyses of symptom cla sses or levels, indicates that light crown symptoms will be difficult to co nsistently detect. However, moderate and severe damage including needle los s (e.g., > 25%) does appear to be detectable. Isolated trees of similar cha racteristics as root rot infected trees do appear on the imagery in scatter ed locations unrelated to root rot activity. It is anticipated that these f alse alarms can be largely mitigated by identifying the characteristic patt ern of root rot damaged trees (i.e., stressed trees around a centre, the ce ntre often being a hole or gap in the canopy).