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r� EUGENE Public Works Maintenance Division City of Eugene 1820 Roosevelt Boulevard M EMORANDUM Eugene, Oregon 97402 (541) 682 -5220 (541) 682 -6883 FAX Date: September 3, 1997 To: Johnny Medlin, Maintenance Support Manager From: Scott Plamondon, Urban Forester Subject: Hendrick's Park Hazard Trees We have spent additional time examining the 18 trees in Hendrick's Park with the citizen group and outside experts; Alan Kanaskie, Oregon State Department of Forestry Forest Pathologist and Mike Cloughesy, Oregon State University Forestry Extension Agent. Following is a synopsis of the meeting and information I received from these two experts. In general, the hazard trees show signs of Phellinus pini - a stem rot. Some of the trees show a minor degree of infection while others show an advanced degree of infection. Both experts stated that Fir tree failure as a result of trunk failure related to this stem fungi is not common. In addition, this stem fungi grows slowly in Fir trees, and a tree can stand for a number of years with this condition. It was their opinion that the fungus is most likely present in all of the trees even though there is no visible evidence on some of the trees in the park. They agreed that the removal of the most decayed of these trees would not promote more tree failures by the opening up of the forest canopy. On the contrary, it was felt that removal would in some instances promote better growth on the remaining healthier trees. This is especially true when the infected tree is a suppressed tree competing with others for light and nutrients. Even though we used a resistograph on the trees, they recommended coring the trees to determine the degree of decay and conducting root crown examination on some of the trees to determine the degree of root rot. Although the resistograph measures electrical resistance in the trees, there is not a 100% relationship with the resistograph and the decay in the trees. We have found the resistograph to be about 80% accurate in the comparisons of the resistograph chart and the core samples we have taken in the past few days at Hendricks. The resistograph indicates the presence of decay but doesn't show exactly the degree of the decay. As we use it more, we will be able to set levels of resistance based on good and decayed wood of various species and with this data have a better handle on the decay within a tree. Coring is allowing us a more accurate and visible examination of the cross section of the trees. We didn't fmd any other cause for the change in resistance; like pitch pockets. Experts can and often do disagree. One of the experts leaned in the direction of retention of some the decayed trees while the other expert leaned in the direction of removal. There was at least one tree that the experts could not agree on; one expert thought the tree should come out while the other expert thought it should remain. They both felt more investigation was warranted with coring of the trunks and root crown examination to determine the degree of decay and rot.