Recovery Plan for the Northern Spotted Owl - DRAFT

Outbreaks of Douglas-fir tussock moth and spruce budworm occurred naturallybut it is thought that management has increased outbreak severity. Suchoutbreaks can cover hundreds of square miles.Swetnam and Lynch (1989) reconstructed the history of spruce budwormoutbreaks in the southern Rocky Mountains from 1700 to 1983 using tree ringanalysis and identified at least nine outbreaks. Severity and timing werehighly variable. The average period of reduced growth was 12.9 years andranged from 5 to 26 years. The average interval between initial years of successiveoutbreaks was 34.9 years and ranged from 14 to 58 years. There was arelatively long period of reduced budworm activity in the first decades of the20th Century but since then outbreaks have been more severe. Currentoutbreaks may be more severe than outbreaks occurring under natural conditions.However, current outbreaks were not clearly less or more frequent thanthose during the previous 2 centuries. This change in severity was related tochanges in age structure and species composition following harvesting and firesuppression in the late 19th and 20th Centuries.Douglas-fir tussock moths also seem to have increased in severity. Althoughnative to North America, tussock moths were not reported defoliating standsuntil 1908. Since that time infestations have occurred synchronously every 8to 10 years over wide geographic areas (Brubaker 1978).Spraying epidemic defoliator populations with chemicals and Bacillusthuringiensis has had little impact.Douglas-fir and pine bark beetle populations all have increased resulting inwidespread mortality across the landscape. Pine tip moth problems also haveincreased, especially in young plantations.Fire suppression, high grading and changes in species succession also havechanged the disease situation; root rot diseases are now extremely damaging,especially Phellinus weird and Annillaria ostoyae (Baker 1988). ArTnllarTa hasbecome extremely damaging in the more stressful environment created by firesuppression. It kills all conifer species and all ages of trees in this subregion.It has increased dramatically as stumps have been created in managed forestswith the subsequent increase in inoculum potential. Mixed conifer forests areoften more severely damaged by root diseases after logging than before logging(Filip 1990, Filip and Goheen 1984). Heterobasidion annosum also has increased.It now causes considerable mortality in pine stands as well as rootand butt rot in true firs. It may even occur in Douglas-fir. Some foliagediseases seem to have increased with management and larch needle blight iscurrently active over a wide area in eastern Washington.Dwarf mistletoes also have increased in managed stands. Fire typicallycleanses forest stands of dwarf mistletoe (Baker 1988). Douglas-fir, true firs,ponderosa pine, and lodgepole pine have become easily infected and now manyof these trees have reached canopy dominance capable of infecting new trees inthe understory. Interestingly, half of the owl nesting sites in the Wenatcheearea of the East Cascades subregion are in dwarf mistletoe-infected Douglas-firtrees. Few of these trees would have existed in natural forests. Forsman et al.(1990) noted that owls utilize north-slope, closed-canopy forest more than thesouth-slope ponderosa pine forests. These mixed coniferous stands retaincharacteristics of mature and old-growth stands, such as snags and downtrees, a moderate to strongly multilayered canopy and heavy infestation ofDouglas-fir dwarf mistletoe. In the Wenatchee National Forest spotted owlswere noted to nest in more or less even-aged Douglas-fir stands 90 to 130years old with a high proportion of Douglas-fir (Buchanan pers. comm.). Thesestands were infected with dwarf mistletoe and more than half the owl nestswere in mistletoe brooms.469