Effects of a warmer climate on stress complexes in forest of western North America.


McKenzie, D., Peterson, D.L., Littell, J.S. 2005. Effects of a warmer climate on stress complexes in forest of western North America. EOS Trans. AGU 86(52); Fall Meet. Suppl., Abstract GC32A.


A warmer climate in western North America will first affect those forests that are most susceptible to soil moisture stress. Increased water deficit will accelerate the normal stress complex experienced in forests, which typically involves some combination of multi-year drought, insects, and fire. Symptoms of prolonged drought and insects are currently manifested in extensive dieback of pine species in the pinyon-juniper forest of the American Southwest, an area where only a few tree species can survive. Less severe dieback has occurred in mixed conifer forests of the Sierra Nevada, an area also subjected to air pollution stress. Bark beetles are proliferating and killing millions of hectares of dry forest in the northern interior of western North America, setting up the prospect of large and intense fires. Recent analyses of area burned by fire in the 11 large Western states of the conterminous United States indicate that fire area will be at least twice as high in the warmer climate predicted by general circulation models. Such a large increase in disturbance superimposed on forests with increased stress from drought and insects may have significant effects on growth, regeneration, and long-term distribution and abundance of forest species.