Two Decades of Carbon Flux from Forests of the Pacific Northwest

arth's climate is greatly influenced by carbon dioxide conE centrations in the atmosphere, which have increased by approximately 25% since the dawning of the Industrial Revolution, when fossi l fuel combustion accelerated greatly (IPCC 1990). Another important anthropogenic source of atmospheric carbon is associated with deforestation, especially in primary forests, which can store large amounts of carbon in the form of organic biomass (Detwiler and Hall 1988, Harmonetal. 1990). Attempts to balance the global carbon budget have indicated that 20%-50% (1-3 Pg/yr) of the carbon released to the atmosphere from anthropogenic sources cannot be accounted for or fully explained (Dale et al. 1991, Dixon et al. 1994, Post et al. 1990, Sarmiento 1993). Recent efforts to decrease uncertainty in global carbon cycling processes have focused on improving estimates of land-use change in the tropics (Dale et al.