80 



"The wholesale killing of American chestnut by blight on thin soils on upper 

 slopes in places in Pennsylvania has in some instances resulted in soil 

 deterioration . . . and centuries may be required to restore the original value of 

 the watershed." (Boyce) The dogwood's leaves contain a large amount of calcium and 

 are important in building rich soils (Hepting 1971). In Oregon and California, Port- 

 Orford-cedar's leaf litter is less acidic and higher in calcium than that of associated 

 conifers, thus probably contributing to desirable soil properties, particularly on 

 ultramafic (serpentine) sites (Zobel et al. 1985). 



Some of the most threatened trees form the foundation for unique micro- 

 ecoystems. The Fra^er fir occupying the highest peaks in the southern Appalachians 



Erovides essential habitat for the very rare spruce fir moss spider and several rare 

 ryophvtes. These species, and probably many more endemic invertebrates, are in 

 jeopardy of becoming extinct with the fir (Langdon). Port-Orford-cedar forests in 

 southern Oregon and northern California form ecologically and floristically unique 

 communities (Zobel et al. 1985). 



POTENTIAL FUTURE INTRODUCTIONS 



New attention is being directed toward introduced forest pests because of the like- 

 lihood that American firms will greatly increase imports of logs or rough-cut lumber 

 in large quantities fi-om other temperate regions to substitute for logs no longer 

 being cut m our National forests. Such imports pose a real threat of introducing ad- 

 ditional damaging forest pests. A risk assessment team that examined proposed im- 

 ports from Siberia estimated losses associated with the possible introduction of just 

 36 "representative" pests of larch (out of 175 pest species identified), at between 

 $24.9 million and $58 billion. These figures represented only the potential impacts 

 to commercial timber species in the western United States; they did not consider 

 ecosystem damage or impacts to nonconsumptive industries associated with forested 

 land. 



The Siberian team stated further: 



Loss of a significant proportion of living trees within stands would trigger 

 complex changes in food supply and habitat . . . Detrital food chains — 

 fueled by dead organic matter — would be favored, while food chains that de- 

 pend on living trees would collapse unless the system recovered very quick- 

 ly. . . ." USDA Forest Service 1991b). 



The risk assessment authors predicted that mycorrhizal fungi, several species of 

 voles, flying squirrels, and spotted owls would be seriously harmed Deer and elk 

 would be further limited by the increased scarcity of closed-canopy forests, which 

 provide winter forage and shelter. Western yew, accipiter hawks, and salmonid fish 

 would also decline (USDA Forest Service 1991b). 



Potentially damaging pests — either not now present in North America or present 

 but possibly of different genetic makeup — were also identified in New Zealand and 

 Chile. These two countries are currently the principal sources of large-scale wood 

 imports — other than Canada. 



RECOMMENDATIONS 



For many years, it has been recognized that the most efficient method to elimi- 

 nate exotic pest infestations is to prevent the organism ft-om entering the country. 

 That task belongs to the Animal and Plant Health Inspection Service (APHIS) of 

 the U.S. Department of Agriculture. 



Quarantines are never completely effective; they often delay rather than com- 

 ple'ely prevent introductions. Nevertheless, such delay is worthwhile because it "de- 

 ters damage or costly readjustment to the intruder [and] also because the new dis- 

 ease can likely be met in the future with a more organized and efficient effort than 

 is possible now." Quarantines are especially important to forestry because of the 

 long period before trees reach maturity, thus slowing development of disease-resist- 

 ant strains (Boyce 1961). 



Unfortunately, the evidence is that APHIS' current efforts are not as effective as 

 thev should be. Sometime before the 1990s, an alien leaf rust which attacks poplars 

 and conifers {Melampsora larici-populina) was introduced on our West coast 

 (Chastagner and Newcombe 1993). Black cottonwood Populus trichocarpa and aspen 

 {Populus tremuloides) and hybrid poplars are commercially important as a potential 

 source of biomass for conversion to alcohol for fuel and for blending with conifers 

 in the production of high-grade paper (Abelson; Chastagner and Newcombe 1993). 



The common (or larger) pine snoot beetle {Tomicus (= Blastophagus) piniperdia) 

 was discovered in 1992 near Cleveland, Ohio (Kucera 1992). This pest has attacked 

 a vfunety of Eurasian and North American pine species. Infestations have been 

 found ft-om western New York through Pennsylvania, Ohio, Indiana, to Illinois, as 



