Nitrogen balances in forest ecosystems of the Pacific Northwest

In order to understand the role of nitrogen in the forests of the Pacific Northwest, especially Douglas-fir, a great number of studies have been initiated to evaluate both static and dynamic aspects of the nitrogen balance. This paper presents a summary of many of these past results covering 20 yr research with the specific intent of defining the nitrogen economy of these systems and the long- and short-term changes that are occurring. Variations of nitrogen in both soils and vegetation are discussed with some sampling techniques applicable to coniferous forests given. It appears that the soil total nitrogen, in different soils, varies several fold more than the nitrogen in the forest crops of these soils. The dynamics of nitrogen transfer within the ecosystem, together with gains and losses from the system, are presented.