Remote sensing of host species distribution in hardwood forests with Sudden Oak Death in Marin and Sonoma counties
Maggi Kelly1 and Ross Meentemeyer2
Marin and Sonoma counties have pockets of extensive oak mortality throughout forest stands, and several of these areas are recognized hot-spot for the disease Sudden Oak Death. The disease type common in these areas causes overstory crown color change and mortality which is visible from above. Airborne Digital Acquisition and Registration (ADAR) imagery was gathered in Marin county in spring 2000, 2001 and 2002, and in Sonoma county in summer 2001. The 4-band (red, green, blue and near infrared) imagery has a ground resolution of 1-meter, sufficient to map individual tree crowns. The imagery was analyzed for hardwood species discrimination, and for individual tree mortality in the study areas using a combination of supervised and unsupervised classification routines. Maps of hardwood species distribution were created. In addition, the spatial pattern of the resulting array of dead tree crowns by year was quantified to demonstrate clustering of the mortality across multiple scales. These data were used in further research that models the underlying environmental factors influencing mortality. This paper presents results from the remote sensing and spatial analyses, and discusses the advantages and challenges of remote approaches to mapping Sudden Oak Death.
1Cooperative Extension Specialist and Adjunct Assistant Professor, Ecosystem Science Division, Department of Environmental Sciences, Policy and Management, UC Berkeley, Berkeley, CA 94720-3110; (510) 642-7272; mkelly@nature.berkeley.edu
2Department of Geography, Sonoma State University, Rohnert Park, CA 94928-3609; (707) 644-2558; ross.meentemeyer@sonoma.edu
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