ABSTRACT
This chapter reviews historical levels of productivity in natural forest stands, increases in yield that have resulted from plantation management, and potential productivity from future technologies, in particular genetic manipulation. Protection efforts have played a vital role in increasing forest yields. Forests consist of mixed pine stands with dense, shrubby undergrowth and may occupy only 30 percent of the area. Maximum productivity for a temperate coniferous forest has been estimated to be at least 45 Mg/ha per year on the basis of a survey of world literature. Although forest soils in the Douglas fir region often contain large amounts of total nitrogen, low mineralization rates due to low average soil temperatures limit its availability to trees. With forestry technology, plantations can achieve 40 percent or 50 percent of the target mean annual yields. In closed-canopy coniferous forests light absorption is more efficient than in agricultural crops.
