Edmonds, Robert L.; Binkley, Dan; Feller, Michael C.; Sollins, Phillip; Abee, Albert; Myrold, David D. 1989. Nutrient cycling: effects on productivity of Northwest forests. In: Perry, D. A.; Meurisse, R.; Thomas, B.; Miller, R.; Boyle, J.; Means, J.; Perry, C. R.; Powers, R. F., eds. Maintaining the long-term productivity of Pacific Northwest forest ecosystems. Portland, OR: Timber Press: 17-35.
Nutrient availability—the quantity of nutrients available for uptake by trees—limits forest productivity. Inthe U.S. Pacific Northwest and British Columbia (the Northwest), nitrogen is the major growth-limiting nutrientelement, although sulfur potentially may be limiting in southern Oregon, potassium in gravelly outwash soils,phosphorus in coastal Washington, and boron and zinc in southwest British Columbia. This chapter examines,with particular reference to the Northwest: (1) characteristics of nutrient-limited stands, (2) the concept ofnutrient availability in relation to nutrient cycling, (3) specific challenges facing forest managers, such asrestoring nutrients after harvest, and (4) management options for maintaining long-term productivity. Thetheory of "optimum nutrition"—providing all necessary elements at a rate determined by tree growth—is dis-cussed. Nutrient-rich sites are generally more robust than nutrient-poor sites, but the nutrient capital even onproductive sites should be conserved by using fire carefully and minimizing soil disturbance during sitepreparation. Weed control generally increases nutrient availability. Maintaining woody debris could be impor-tant in managed plantations. Foresters are encouraged to install "low-intensity" nutrient experiments to testideas on maintaining productivity.