Editing Douglas fir (section)

=== Preferred sites ===
Douglas-fir prefers acidic or neutral soils, such as [[Olympic (soil)|Olympic soil]].<ref>{{cite web |url=https://www.arborday.org/trees/treeguide/treedetail.cfm?itemID=836 |title=Douglas-fir Tree on the Tree Guide|work=arborday.org}}</ref> However, it exhibits considerable morphological plasticity, and on drier sites ''P. menziesii'' var. ''menziesii'' will generate deeper taproots. ''Pseudotsuga menziesii'' var. ''glauca'' exhibits even greater plasticity, occurring in stands of interior temperate rainforest in British Columbia, as well as at the edge of semi-arid sagebrush steppe throughout much of its range, where it generates even deeper taproots still.

The coast Douglas-fir variety is the dominant tree west of the Cascade Mountains in the [[Pacific Northwest]]. It occurs in nearly all forest types and competes well on most parent materials, aspects, and slopes. Adapted to a more moist, mild climate than the interior subspecies, it grows larger and faster than Rocky Mountain Douglas-fir. Associated trees include [[western hemlock]], [[Sitka spruce]], [[sugar pine]], [[western white pine]], [[ponderosa pine]], [[grand fir]], [[coast redwood]], [[western redcedar]], [[incense-cedar|California incense-cedar]], [[Chamaecyparis lawsoniana|Lawson's cypress]], [[tanoak]], [[bigleaf maple]] and several others. Pure stands are also common, particularly north of the [[Umpqua River]] in Oregon. It is most dominant in areas with a more frequent fire regime that suppresses less fire-resistant conifers.<ref name=":1" />