ing most trees, such as in the Tillamook burn 

 in the 1930s. These large fires are usually as- 

 sociated with drought years and warm dry 

 winds. Douglas-fir establishes well after in- 

 tense fires, and many present-day Douglas-fir 

 forests owe their beginnings to fire. The earli- 

 est Douglas-fir plantations were established 

 after a fire in the Coast Range around 1915. 



Wind and root disease cause wind- 

 throw — ^Periodic severe windstorms, typically 

 between October and March, can cause exten- 

 sive windthrow. Root disease and stem decay 

 are the most common biological factors pre- 

 disposing trees to windthrow. If blown down 

 trees are Douglas-fir, the Douglas-fir beetle is 

 likely to attack and kill standing trees for 2 

 years after a windstorm. During an outbreak, 

 the beetle typically kills about one live tree for 

 every three or four that were windthrown. Mor- 

 tality can be prevented if windthrown trees are 

 salvaged or beetle repellents used. This inter- 

 action of wind, root disease, and bark beetles 



creates canopy gaps, mixes soils during tree 

 uprooting, and increases structural and bio- 

 logical diversity in stands. 



The November 1995 windstorm in Oregon 

 blew down trees on thousands of acres in the 

 Coast and Cascade ranges. Mortality caused 

 by Douglas-fir beetle is expected in areas where 

 trees are not salvaged or protected. 



Douglas-Fir 

 Douglas-Jir is plagued by root diseases — 



Laminated root rot, a native disease that af- 

 fects many conifer species, is the most wide- 

 spread and destructive disease of Douglas-fir 

 in the Coast Range and western Cascades. 

 Various surveys estimate that, on average, 

 patches of lam^inated root rot occupy 3 to 5% 

 of the Douglas-fir forest, but the disease is dis- 

 tributed unevenly. Many stands in the north- 

 ern Coast Range have more than 1 5% of their 

 area occupied by root disease patches. 



Stem decay — too much or too little? As stands 

 mature, decay organisms cause tree death or 

 breakage, creating gaps in the canopy and providing 

 rotten wood and hollow logs that are used by 

 wildlife. Although there are benefits to wildlife, 

 decay and stain can severely reduce timber value. 

 In managed western Oregon stands, the harvest of 

 old trees has decreased the average tree age and 

 amount of decay, especially on private lands. A 

 concern in areas with extensive young stands may 

 now be the lack of decay and defect and its prob- 

 able effect on wildlife and ecosystem processes. 



The amount of decay in trees depends on tree 

 species (some species are more susceptible than 

 others), and generally increases with the frequency 

 of wounding, and the size and age of the wound. 

 The amount of decay in a stand can be reduced by 

 keeping rotations short and avoiding tree injury 

 during management activities such as thinning. 

 Decay can be increased by intentionally damaging trees, retaining defective trees, and 

 inoculating trees with wood decay fungi The tradeoff between wood production and 

 rotten wood for wildlife needs must be balanced through thoughtful long-range planning. 



Decay provides habitat for wildlife. 



■:,n. >'-<A-^-\i: 



Oregon — 26 



