Ecological dynamics

The grand fir/cool moist forb (GF -CMF) ecological site (ES) encompasses the modal grand fir (Abies grandis)/queen’s cup beadlily (Clintonia uniflora) plant association (ABGR/CLUN) , and the closely related grand fir/Pacific yew (Taxus brevifolia)/queen’s cup beadlily plant association ABGR/TABR/CLUN). Pacific yew forests are a moist microsite association, with longer fire return intervals compared to queen’s cup beadlily associations.
This ecological site occupies the wetter and cooler end of the moisture/temperature spectrum for the grand fir series. It’s found on moist, well-drained sites which are protected from harsh sun and wind. The GF-CMF site is transitional to colder subalpine fir (Abies lasiocarpa) forests in an increasing moisture/temperature gradient.
The Douglas-fir (Pseudotsuga menziesii)/big huckleberry (Vaccinium membranaceum) (PSME/VAME) plant association, relatively modest in extent, is also included in the GF-CMF ecological site group. The main reason for assigning this particular association to the ES is because the historic fire regime is very similar to that of the two grand fir plant associations, and therefore the primary driver of the ecological processes forms the logical link.
The big huckleberry Douglas-fir association is the wettest expression of the Douglas-fir series. It also shares many attributes of the Douglas-fir warm dry shrub (DF-WDS) ecologic site (which is represented by the modal Douglas-fir/ninebark (Physocarpus malevaceous) plant association, abbreviated as PSME/PHMA). The expression of conifers within the PSME/VAME member is skewed to the warmer Ponderosa pine and Doug-fir, and away from the cooler and more moist larch and grand fir.
This ecological site is floristically diverse and has a wide range of seral plant expressions which can develop following disturbance. The specific plant occupancy will vary according to the initial composition of the stand, the individual surviving trees, along with specific sources of seeds (especially conifer species) the surviving root or rhizomes of adapted understory plants. The type and extent of the disturbance event determines post-fire recovery opportunities, along with the passage of time.
Ponderosa pine (Pinus ponderosa), western larch (Larix occidentalis) and lodgepole pine are the primary early seral species following widespread, stand replacing disturbance events in the modal expression of the ecological site. Doulas-fir and Western white pine (Pinus monticola) are dominant mid seral conifers, and Englemann spruce (Picea engelmannii) is a late seral species. Douglas-fir is well represented in all three plant associations that comprise the ecological site. Grand fir is the climax conifer of the ecological site, but Doug-fir and grand fir will commonly co-exist as the late stage dominant overstory species while grand fir typically shows the greater expression of the two species. Western white pine and western larch are not well represented in the Pacific yew type of the grand fir PVT, and western white pine is not a common component in the moist Douglas-fir association. The historical occurrence of western white pine historical was limited to the modal plant association essentially. Western white pine has been very restricted in expression and ecological function since the introduction of white pine blister rust (Cronartium ribicola) to the United States in the early part of the 21st century. Regardless of the exact progression from one plant community stage to another, mature stands in this site develop as predominately uneven-aged forests.
Pacific Yew has a growth form of a small tree or a shrub, depending on site conditions in which is found. Pacific yew establishes in in moister microenvironments and therefore has a longer fire return interval than the other plant association members of the ecologic site. The species has been reduced in extent following high levels of bark harvest because of the cancer inhibiting properties of the plant.
Shrubs such as common pipsissewa (Chimaphila umbellate), twinflower (Linnea borealis), Oregon boxwood (Pachistima myrsintes), baldhip rose (Rosa gymnocarpa), common snowberry (Symphoricarpos albus) and big huckleberry (Vaccinium membranaceum) are common.
Insect and disease agents that are important in this site include fir engraver, Douglas-fir beetle, dwarf mistletoe, root diseases and defoliating insects including spruce budworm, Douglas-fir tussock moth, and larch casebearer. These are usually small to mid-scale in scope unless the disturbance reaches an epidemic stage.
Overall, fire was the major historic disturbance factor in the ecological site. Ponderosa pine, western larch and lodgepole pine were common early seral conifers that established following mixed or stand replacement fire events.
Fire exclusion within the past 100 years (the “post-European” time frame) has drastically altered the structural expression of the present forest, resulting in an increase in ladder fuels and in overall fuel levels. This, in turn, increases the risk of more widespread, catastrophic wildfires in this forest type.