USDA Forest Service:
1935. Drawing shows Keen's ponderosa pine tree classification - for comparison of bark beetle susceptibility classes based on age and vigor.
USDA Forest Service:
1934. Class 1A. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 1A. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 1A and 1D. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 1B and Class 2B. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 1B. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 1C. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 2A and Class 1C. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 2B. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 2C. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 2D and Class 3D. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 3A in Keen's ponderosa pine tree classification, used for comparison of bark beetle susceptibility classes based on age and vigor.
USDA Forest Service:
1934. Class 3A. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 3A. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 3A. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 3A or Class 4A. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 3B. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. In the Portland Station Collection's documentation, this image is classified as Class 4B or Class 3B. It's also documented this way in the Bureau of Entomology Collection's documentation, but then those are crossed out and replaced with a Class 3C.
USDA Forest Service:
1934. Class 3C or Class 4C. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 3C and 2C. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 3C and Class 2C. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 3C. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 3C. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 4A. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 4B. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 4B. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 4B. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 4B. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 4C. Tree Selection. Keen Ponderosa Pine Tree Classification.
USDA Forest Service:
1934. Class 4C or 3C. Tree Selection. Keen Ponderosa Pine Tree Classification.
