. Hazard-rating systems in forest insect pest management : symposium proceedings, Athens, Georgia, July 31-August 1, 1980. Forest insects Biological control United States Congresses; Forest insects United States Analysis; Forest insects United States Management. for the si "I vicultural objective of reducing mortality and increasing net growth. of the California System resolved this problem. 2 3. B CD Figure Keen ponderosa pine tree classification. Age increases from 1 to 4 and vigor decreases from A to D. (From Keen 1936. ) From 1928 to 1931 an impressive study was conducted in s
. Hazard-rating systems in forest insect pest management : symposium proceedings, Athens, Georgia, July 31-August 1, 1980. Forest insects Biological control United States Congresses; Forest insects United States Analysis; Forest insects United States Management. for the si "I vicultural objective of reducing mortality and increasing net growth. of the California System resolved this problem. 2 3. B CD Figure Keen ponderosa pine tree classification. Age increases from 1 to 4 and vigor decreases from A to D. (From Keen 1936. ) From 1928 to 1931 an impressive study was conducted in southern Oregon, near Ashland, in which 27,465 attacked trees were classified according to the Keen Tree Classes; and 22,428 unattacked trees were classified for comparison. The results showed a distinct improvement over the use of Dunning's vigor classes. Mortality ratios found ranged from for trees with a high vigor classification to for trees with a low vigor classification. The mortality ratio is the percentage of the loss in a given class divided by the percentage of that class in the original stand. Mortality ratios >1 denote suscep- tible classes. Therefore, the Keen Tree Classes provided, for the first time, a sharp and easily recognized difference among types of crown classes. However, there were too many trees in the suscep- tible classes, requiring the removal of too much of the stand. The development It is interesting to note that Dun- ning' s classes were developed for ponderosa pine on the west slope of the Sierra Nev- ada, where the California System has been found unsuitable. Ecologically, east and west slope Sierra Nevada-Cascade have proved to be two quite different areas for ponderosa pine, and the insect com- plexes appear to be different and to oper- ate differently in the two regions. This variation in site emphasizes the need to establish a sound ecological basis for risk studies. An Insect Selection Cutting Person shifted his base of operatio
Size: 1261px × 1983px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorunitedstatesforestservice, bookcentury1900, bookcollec
