2. Setting the Stage: Vegetation Ecology and Dynamics

The moist coniferous forests of the Pacific Northwest are notable for the dominance of long-lived evergreen conifers, productivity, and the massiveness of the older forests (Franklin and Dyrness 1988; Franklin and Halpern 2000) (plate 2A). The environment of this region is extremely favorable to forest growth, with its moderate temperatures, high precipitation, and relatively fertile soils. The dominance of evergreen conifers is unusual, however, as most moist temperate forest regions of the world are dominated by hardwoods (angiosperms) (e.g., Kuchler 1946; Askins 2014). The climate allows photosynthesis to occur on essentially a year-round basis, which has been identified as one factor favoring evergreen conifers (Waring and Franklin 1979). Although the high productivity of the forests is important, the massiveness of the older forests is as much the consequence of the dominance of tree species present in these forests: for example, Douglas-fir is capable of continuous growth over many centuries and also produces decay-resistant heartwood, which persists for several more centuries. Hence, older forests have accumulations of organic matter (biologically sequestered carbon) that are among the greatest in the world (plate 1B).