Lessons learned in historical mapping of conifer and oak in the north coast

摘要: Conifer encroachment into oak woodlands is becoming a pressing concern for oak conservation, particularly in California's north coast. We use Object-Based Image Analysis (OBIA) with historical aerial imagery from 1948 and recent high-spatial-resolution images from 2009 to explore the potential for mapping encroachment using remote sensing. We find that pre-processing historical aerial imagery is time-consuming and that OBIA requires training and experience but has promise for mapping the phenomenon of interest. We also find that identifying conifer and oak in the imagery without ground-based information is not consistently possible. We recommend iterative mapping and field work, both for obtaining field samples to map encroachment and for mapping woody versus herbaceous cover as a way to screen for locations with potential oak recruitment.