Monitoring Sudden Oak Death in California Using High-resolution Imagery

The Sudden Oak Death (SOD) epidemic in California is alarming for those living with, and adjacent to, the complex of oak and tanoak woodland that exist in patches along the coast. Monitoring SOD occurrence and spread is an on-going necessity. Remote sensing methods have proved to be successful in mapping and monitoring forest health and distribution when a sufficiently small ground resolution is used. In this project, digital high-resolution (1-m) ADAR imagery was analyzed for an area including and surrounding China Camp State Park in Marin County, California in the spring of 2000 and 2001. This paper reports on two analyses: First, the individual frame data from 2000 was mosaiced and classified to reveal 5,340 dead and dying trees in the area including and surrounding China Camp State Park. Second, a smaller subset of the study area was used to perform a Normalized Difference Vegetation Index (NDVI) image differencing and thresholding routine between 2001 and 2000. This change detection showed trees that were misclassified in the 2000 image, as well as newly dead trees. For the smaller study area (303 ha) there were 1,091 dead or dying trees in March 2000, and 317 trees that died in the 13 months that followed. Trees that died between March 2000 and May 2001 were located between 5 and 52 m away from existing dead trees.