Table 3. Examples of agents of change and their effects in frequent-fire, old-growth conifer forests of the western United States


Agent Examples of
potential effects
Reference
Fire-regime disruption
Fire exclusion Increase tree density Stephenson 1999
Increase fire severity Eradicate old trees Savage and Mast 2005
Ranching
Livestock grazing Reduce palatable plants Clary 1975
Fragmentation Restrict wildlife movements Milchunas 2006
Watershed disruption Damage/eradicate springs Belsky and Blumenthal 1997
Wood harvesting
Large-tree removal Reduce some wildlife habitat Tecle and Covington 1991
Road building Spread exotic plants Fornwalt et al. 2003
Fuelwood harvest Affect oak structure Fulé et al. 1997
Other
Predator control Regional species extinctions Dahms and Geils 1997
Exotic plants Reduce some native plants Keeley 2006
Urban development Fragmentation Dale 2006
Climate change Increase tree mortality Breshears et al. 2005