Our classification consists of 14 plant associations and 5 community types in Mount Rainier National Park (Table 1). Several of these have phases to identify subtypes. In addition, separate data are provided for seral groupings (consisting mostly of immature forest stands) of plots representative of several associations. Several minor forest communities are recognized which occur on special soils or landforms or which have restricted distribution in the Park.
Table 1. Classification of forests in Mount Rainier National Park.
We must remind readers that our plant associations are regarded as vegetational expressions of particular environments or habitat types (see previous chapter). The location of 14 of the associations within an idealized environmental field is illustrated in Figure 11. Correspondence between the associations and traditional forest zones is also shown in Figure 11 and Table 1. The patterns of plant association distribution over elevational and topographic gradients will be discussed in more detail in Chapter 6.
Each of the forest associations and community types (collectively referred to hereafter as forest types) is discussed in this chapter. Descriptions of each forest type include general environmental conditions, geographic range within the Park, and tree and understory composition. Successional patterns are considered primarily in Chapter 7. Management implications are considered in Chapter 8. Tables 2 through 10 summarize quantitative details for each forest type. The appendix contains keys to and a brief synopsis of each forest type. The general geography and importance of the forest associations is illustrated by Plate 1. A directory of the individual plots, their locations, and characteristics is available on request from Dr. Jerry F. Franklin, College of Forest Resources, AR-10, University of Washington, Seattle, WA 98195.
In the discussions of each forest type, we point out relationships to other forest types both within the Park and on a broader geographic basis. We regard forest types to be related by several criteria. They may share many, though not all, dominance relationships among tree and understory species. Hence there is a high degree of floristic similarity, especially among the species important in characterizing the forest types being compared. Secondly, the forest types being compared on a broad geographic basis may share many environmental features, although we usually lack data to make precise comparisons or to analyze compensating environmental features at different locations. On a narrower geographic basis (for example, within Mount Rainier National Park), forest types can be related by either of these criteria, but we have the additional advantage of being able to observe ecotones or to firm up the relationship by identifying plots which are gradational in either floristic or environmental characteristics.
Forest types are arbitrarily grouped into five categories so that closely related types are together (Table 1); the association and stand tables are also organized by these groups. Types could sometimes have been assigned to either of two groups (e.g., Abies amabilis/Xerophyllum tenax to either the dry or cold group); such types are included in both appropriate association tables for the reader's convenience in comparing related types. All three of the Pseudotsuga menziesii communities are included in the dry group so that they can be discussed together.
Moist Forest Ecosystems
Five associations and one community type are included in the wet to moist group of forest communities (Table 1). These types occupy habitats where trees rarely encounter significant moisture stress and represent a moderate elevational gradient (Fig. 11). Understories are typically lush, which may reflect the favorable moisture conditions. Extremely wet forests or swamps are briefly discussed in the section on "Other Forest Communities."
Tree data (average size class distributions, percent presence. and average basal area) are presented for this group of forest communities in Tables 2 and 3. Presence and average cover of shrubs and herbs in the wet habitat group are presented in Table 4.
Table 2. Average basal area by tree species for all forest types. Mount Rainier National Park1
Table 3. Average tree density (stems per hectare) for the moist forest types by species and stem-diameter class, Mount Rainier National Park.
Table 4. Constancy and characteristic cover of all shrub and herb taxa for the moist forest community types of Mount Rainier National Park.
Tsuga heterophylla/Achlys triphylla Association
The Tsuga heterophylla/Achlys triphylla Association (TSHE/ACTR) is confined to low elevations on the east side of the Park. Most of our sample plots are located in the Ohanapecosh Valley, but the type also occurs in the White River drainage. Elevation of the plots ranges from 550 to 1080 m (1,815 to 2,900 ft) and nearly all plots are on gentle, lower slopes or sites on valley bottoms. Soils are consistently weakly developed podzols in tephra deposits (typically tephra W over C).
Mature forests are quite dense and strongly dominated by Pseudotsuga menziesii (Fig. 12 and Table 3), with Tsuga heterophylla and Thuja plicata as major associates, although this characterization probably reflects the preponderance of samples in the 250-year-old stands of the lower Ohanapecosh Valley. Abies amabilis is a minor species. Tsuga heterophylla invariably makes up most of the seedlings and saplings.
Three-layered understories are typical of TSHE/ACTR Association (Table 4). A tall shrub layer of Berberis nervosa, Vaccinium parvifolium, V. alaskaense, Rosa gymnocarpa, and Gaultheria shallon provide a total average shrub cover of 57 percent. The well-developed herb layer (see Fig. 12) (average cover 56 percent) is rich in species. Achlys triphylla, Viola sempervirens, Linnaea borealis, Cornus canadensis, and Tiarella unifoliata dominate. Rubus ursinus, Smilacina stellata, Trillium ovatum, Chimaphila umbellata, Disporum oreganum, Rubus lasiococcus, R. nivalis, R. pedatus, Pteridium aquilinum, and Polystichum munitum are other common herbaceous species.
No young stands were sampled on this habitat. Pseudotsuga is obviously a major dominant in young stands. We suspect that some of the stands assigned to the Pseudotsuga menziesii/Viola sempervirens community type are representative of early stages of forest development of the TSHE/ACTR type.
The dense, middle-aged stands of Pseudotsuga are an outstanding feature of this forest type. It is not particularly resilient under heavy use because most understory plants are quite susceptible to trampling and soil compaction; much of Ohanapecosh Campground occurs in this habitat type.
The TSHE/ACTR type is related geographically and floristically to the Berberis nervosa phase of the Abies amabilis/Vaccinium alaskaense and, to a lesser degree, the Tsuga heterophylla/Gaultheria shallon and Abies amabilis/Berberis nervosa associations. The low elevation and sparsity of Abies amabilis distinguishes TSHE/ACTR from the Abies amabilis Series. The rich herb cover and low cover of Gaultheria distinguish TSHE/ACTR from Tsuga heterophylla/Gaultheria shallon.
Comparable forest types have not been described elsewhere in the Cascade and Coast Ranges. Indeed, the geographic limitation of TSHE/ACTR type in the Park and the occurrence of most plots in a 250-year-old age class raise questions as to its validity as an association. Similar stands on the eastern slopes of the Cascade Range indicate that it is. at least, a widespread forest community if not climax type. The TSHE/ACTR is similar to the Tsuga heterophylla/Clintonia uniflora Association of the northern Rocky Mountains (Daubenmire and Daubenmire 1968, Pfister et al. 1977) and to Franklin's (1966) Abies amabilis/Achlys triphylla Association of the Mount Adams region.
Tsuga heterophylla/Polystichum munitum Association
The Tsuga heterophylla/Polystichum munitum Association (TSHE/POMU) and its Abies amabilis phase is a moist hillslope association confined to the western third of the Park where precipitation is higher. The typical TSHE/POMU type is found at elevations up to about 850 m (2,800 ft) in the Carbon, Mowich, Puyallup, and Nisqually drainages. It generally occupies moderate to steep lower slopes or sloping benches with southerly aspects, although three plots were on flat valley floors. Soils are developed in alluvium, colluvium, lahar, and tephra deposits and are frequently stony.
Mature stands in the TSHE/POMU type often have high densities of large trees (Fig. 13 and Table 3). Pseudotsuga menziesii, Tsuga heterophylla, and Thuja plicata are essentially the only species present except for a scattering of small Abies amabilis. Tree reproduction is over 90 percent Tsuga heterophylla, assuring it of climax status. Thuja reproduction is usually present but only in small numbers.
The understories of stands belonging to the TSHE/POMU Association are moderately developed with cumulative shrub cover of 22 per cent and herb cover of 59 percent in the Tsuga heterophylla phase (Table 4). Berberis nervosa is the major shrub with Acer circinatum second. Polystichum munitum is the conspicuous dominant and major understory herb (see Fig. 13). Typical associated herbs are Tiarella unifoliata, Gymnocarpium dryopteris, Achlys triphylla, Viola sempervirens, and Trillium ovatum. Taxus brevifolia occurs in about half the plots of this forest type and averages 3 percent cover (but may be as high as 25 percent).
The Abies amabilis phase of this association can be weakly differentiated by the increased importance of the fir in regeneration and pole densities (Table 3). In the understory, the fern Blechnum spicant may dominate the herb assemblage or be codominant with Polystichum munitum (Table 4). There are no consistent site differences between plots of the Abies amabilis phase and those of the more typical Tsuga heterophylla phase, although the 10 plots of the former averaged about 106 m (350 ft) higher in elevation than the 12 plots of the latter.
No young stands were sampled on this TSHE/POMU habitat type. We suspect that brushfields would develop early in succession following a disturbance, followed by either stands of conifers (Tsuga, Pseudotsuga, and Thuja) or hardwoods (Alnus rubra). Perhaps the Pseudotsuga menziesii/Polystichum munitum and Alnus rubra/Polystichum munitum community types of del Moral and Long (1977) suggest the structure and floristics of young stands in the Park.
The TSHE/POMU is a very limited type in the Park. Its outstanding features include the fine stands of large old-growth Pseudotsuga menziesii, which have very high biomasses. We suspect the TSHE/POMU habitat type is the most productive in the Park since it occupies low elevation, well watered sites with warm southerly aspects. Similar forest communities are common on both the Snoqualmie (Henderson and Peter 1981) and Gifford Pinchot (Topik et al. 1985) National Forests.
Tsuga heterophylla/Oplopanax horridum Association
The luxuriant and often massive forests of the Tsuga heterophylla/Oplopanax horridum Association (TSHE/OPHO) occur in all the major valleys of the Park. This association occupies wet benches, terraces, and lower slopes at low elevations. TSHE/OPHO sites extend to about 690 m (2,280 ft) in the Carbon River drainage and 970 m (3,200 ft) in the Nisqually-Ohanapecosh drainage. Alluvial soils lacking distinctive horizons are most common. Because most sample plots are on essentially flat ground, the aspects vary widely and are insignificant.
Mature forests are typically impressive, high volume stands of Pseudotsuga menziesii, Thuja plicata, and Tsuga heterophylla (Table 3). Tsuga is by far the most numerous, but large specimens of Pseudotsuga and Thuja contribute disproportionately to the basal area. Picea sitchensis is found in this association near the Carbon River entrance and in several plots in the Federation Forest State Park along the lower White River. Abies grandis occurs in the Nisqually and White River drainages. Scattered Alnus rubra and Populus trichocarpa provide a minor hardwood component. Tsuga heterophylla dominates the reproduction with some Thuja plicata and Abies amabilis seedlings and saplings (Table 3). There are many stands where reproduction of any tree species is rare, possibly due to the dense vegetative competition.
Understories in the TSHE/OPHO Association have luxuriant herbaceous layers (summed, their average cover is 116 percent) (Fig. 14) and shrub layers that vary from essentially absent to very dense (average cover 35 percent) (Table 4). Major shrub species are Acer circinatum and Oplopanax horridum, but their cover ranges from a trace up to 90 and 40 percent, respectively. Herb dominants include Gymnocarpium dryopteris, Achlys triphylla, Tiarella unifoliata, Polystichum munitum, Athyrium filix-femina, Galium triflorum, and Smilacina stellata. Several other distinctive species occasionally occur in this association and some, such as Oxalis oregana, can have substantial coverage; their presence is low, however. In fact, none of the dominant herbs are present in all stands (Table 4). Substantial shifts in herb dominants take place between stands, and considerable patchiness is often present within a stand. For example, coverage of Gymnocarpium dryopteris, Oxalis oregana, and Achlys triphylla in different plots of TSHE/OPHO Association range from zero to 80, 80, and 60 percent, respectively.
Few young stands were sampled in this habitat type. Several of these were grouped in the Alnus rubra/Rubus spectabilis community type which appears to be a major successional forest on the TSHE/OPHO habitat type. Young conifer forests, typically composed of Tsuga heterophylla, Pseudotsuga menziesii, Thuja plicata, and Abies grandis, can also be expected following disturbances, along with Populus trichocarpa, provided they can get established before the Alnus.
The TSHE/OPHO Association characterizes one of the habitats that supports the massive valley forests encountered by visitors entering the Park's entrances. The rich understory provides diversity as well as forage for deer and especially for elk (Cervus elaphus). Ponds, seeps, and streams associated with this habitat make it a prime site for amphibians. The sometimes wet soils, high water tables, and above average windthrow are considerations when planning physical developments in this habitat type.
The TSHE/OPHO Association may border or form ecotones with a variety of Tsuga heterophylla and Abies amabilis forest types at lower elevations. The most common contact is probably with the slightly drier TSHE/POMU Association in the western half and the TSHE/ACTR Association in the eastern half of the Park.
Park associations most closely related to the TSHE/OPHO are Abies amabilis/Oplopanax horridum, TSHE/POMU, and TSHE/ACTR associations. The TSHE/OPHO grades into the Abies amabilis/Oplopanax horridum with increasing elevation and differs mainly in the abundance of Abies amabilis. The TSHE/POMU Association is generally found on slopes and contains neither as rich an herbaceous cover nor diversity of species as does TSHE/OPHO. The TSHE/ACTR occupies substantially drier uplands and is much poorer in species than the TSHE/OPHO Association.
Communities related to TSHE/OPHO Association have been reported from several other locales throughout the Pacific Northwest. It is closely related to the Western Hemlock/Devil's Club/Swordfern Association on the Gifford Pinchot National Forest (Topik et al. 1985). Some stands of Thuja plicata found in the valley bottoms of North Cascades National Park are of this habitat type.2 Comparable stands occur in coastal British Columbia (Krajina 1965). The Thuja plicata/Oplopanax horridum habitat type of northern Idaho (Daubenmire and Daubenmire 1968) and western Montana (Pfister et al. 1977) also appears to be comparable.
Alnus rubra/Rubus spectabilis Community Type
The Alnus rubra/Rubus spectabilis community type (ALRU/RUSP) identifies the seral Alnus rubra stands that develop on the TSHE/OPHO, low elevation Abies amabilis/Oplopanax horridum, and perhaps, TSHE/POMU habitat types following disturbance. The ALRU/RUSP community type can occur in any of the Park's valleys, but our sampled stands were in the Cowlitz and Nisqually River drainages. Range in elevation is up to at least 810 m (2,650 ft). Flat or gently sloping benches on valley bottoms and terraces with alluvial soils are typical.
Stands of the ALRU/RUSP type are, by definition, dominated by Alnus rubra (Fig. 15 and Table 3). Conifer associates may be absent, few, or codominantdepending mostly on stand history. Associates can include Tsuga heterophylla, Thuja plicata, Pseudotsuga menziesii, and Abies amabilis. Tree reproduction is typically absent or, at best, sparse; it often consists of seedling or sapling Tsuga or Thuja which were overtopped by Alnus early in the stand's history but have persisted. The absence of substantial tree reproduction by any species have led some ecologists to hypothesize that such stands turn into shrub-fields of Rubus spectabilis as the short-lived Alnus dies out (Franklin and Dyrness 1973).
The understory in ALRU/RUSP stands has luxuriant shrub and herb layers (Table 4). Rubus spectabilis is the major shrub, although many others such as Oplopanax horridum, Sambucus. Rubus parviflorus, and Ribes bracteosum may be present in substantial amounts. Herbaceous cover is always high and highly varied in composition; typical important species include Athyrium filix-femina, Achlys triphylla, Circaea alpinum, Tiarella unifoliata, Pteridium aquilinum, Gymnocarpium dryopteris, Viola glabella, Rubus lasiococcus, and Cinna latifolia.
This community appears to be important wildlife habitat. Several stands were sampled in The Burn in the Cowlitz River drainage (where it is most extensive) and all were being heavily used by elk. Such communities are prime habitat for rodents such as mountain beaver.
Communities similar to the ALRU/RUSP are widespread on cutover and burned-over forest lands in western Washington and Oregon (Franklin and Dyrness 1973, Henderson 1978). The successional development of these stands is not understood, although it appears that both shrubfields and conifer stands are alternatives, depending on circumstances. In western Oregon, Henderson (1978) found little evidence of conifers replacing 64 years of alder dominance despite a declining crown closure in the alder overstory as the sere progressed. The ALRU/RUSP community does deter conifer development. Extensive examples of the type are seen on cutover lands along all the highways approaching the Park from the west, including the Mowich Lake road. Many such stands on private lands are being converted to conifer forest by felling, burning, and planting.
Abies amabilis/Oplopanax horridum Association
The primary TSHE/OPHO Association on wet valley bottom benches, terraces, and lower slopes gradually changes with higher elevations to the Abies amabilis/Oplopanax horridum Association (ABAM/OPHO). Stands are still richly vegetated but have Abies amabilis as a regular component. The overall elevational range of the 33 study plots is from 650 to 1190 m (2,145 to 3,900 ft) for stands on the valley bottoms and 810 to 1460 m (2,670 to 4,820 ft) for those on mountain slopes. The transitional elevation from TSHE/OPHO to ABAM/OPHO is lowest in the Carbon River drainage (about 650 m or 2,150 ft), intermediate in the Nisqually and Ohanapecosh drainages (around 750 m or 2,500 ft), and highest in the White River drainage (around 900 m or 3,000 ft). Stands of the ABAM/OPHO Association on valley bottoms occupy gentle (0 to 20 percent slope) terraces and benches with varying aspects. High-elevation stands are most commonly found on steep (23 to 75 percent), lower slopes with northerly aspects but may occur on south aspects (especially near the upper limits of the habitat type) and on midslopes or even upper slopes. Soils in valley bottom stands are generally developing on alluvium and lahar surfaces. They vary widely in morphology from deep, nondescript layers of gray sand to distinctive podzolic profiles. Soils of slope stands have stony colluvial (most common), alluvial, and tephra parent materials (Hobson 1976).
Mature forests of valley bottoms typically are impressive with massive specimens of Thuja plicata and Pseudotsuga menziesii mingled with more numerous Abies amabilis and Tsuga heterophylla (Fig. 16 and Table 3). Other species encountered in minor quantities are Picea engelmannii, Abies procera, and Chamaecyparis nootkatensis. Taking all stands into consideration, seedlings of Abies amabilis and Tsuga heterophylla are about equally abundant whereas Abies amabilis has clear superiority in saplings. In fact, there is wide variation in both the total amount and species composition of tree reproduction which is at least partially related to the severe competition from shrubs and herbs.
Abies amabilis dominates mature stands on slopes with Tsuga heterophylla as the major associate. Large specimens of Thuja plicata, Abies procera, or Picea engelmannii are occasionally encountered. One stand at a very high elevation contained considerable Tsuga mertensiana. Reproduction in stands of ABAM/OPHO on slopes is more uniformly abundant than on the valley bottom. Abies amabilis dominates although Tsuga heterophylla is still important, suggesting it has at least a minor climax role.
The understory of the ABAM/OPHO Association is always luxuriant on valley bottoms and, as with the TSHE/OPHO. is rich in species (Table 4). The composition and structure vary widely, however. Some stands have a continuous carpet of herbs with essentially no shrub layer, whereas others have a dense tangle of Oplopanax horridum, Rubus spectabilis, and Vaccinium spp. (see Fig. 16). The shrub layer averages 32 percent in valley bottom stands with Oplopanax, Vaccinium alaskaense, Vaccinium ovalifolium, and Rubus spectabilis the most important species. The dense herb layer (average cover 79 percent) has Gymnocarpium dryopteris, Achlys triphylla, Tiarella unifoliata, Rubus pedatus, Streptopus roseus, and Athyrium filix-femina as important species. There is, however, substantial patchiness within stands and shifts in the herb dominants between stands; for example, Gymnocarpium varies from 0 to 90 percent cover.
The understory of ABAM/OPHO stands on slopes is similar to that of valley bottom stands, with 35 percent shrub and 93 percent herb covers. Ribes lacustre has more importance on slopes than on valley bottoms. Acer circinatum is not common, but, as on the valley bottom, may have considerable coverage when present. Tiarella unifoliata increases in importance, essentially replacing Tiarella trifoliata. More typical mountain slope species, such as Rubus lasiococcus and Viola glabella, are also more common; but Gymnocarpium dryopteris, Achlys triphylla, Streptopus roseus, and Athyrium filix-femina remain important.
Few young stands were sampled on the ABAM/OPHO Habitat Type. It appears that valley bottom sites can develop stands partially or wholly dominated by Alnus rubra following disturbance, at least at the lowest elevations. These forests belong to the ALRU/RUSP community type discussed earlier. Young conifer stands of highly variable composition can also develop immediately following disturbance. These are as likely to be dominated by shade-tolerant species such as Abies amabilis and especially Tsuga heterophylla as they are by so-called pioneer species such as Pseudotsuga menziesii or Abies procera. Early stages in succession will generally have dense shrub covers of Rubus spectabilis, R. parviflorus, Sambucus, and Salix spp.
The special features of the ABAM/OPHO Association are much the same as those of the TSHE/OPHO. It is a rich and productive environment where the most massive forests and largest individual trees in the Park are encountered. Most of the very old stands (800 years or more in age) known in the Park belong to the ABAM/OPHO Association. It provides important wildlife habitat and is heavily used by elk except when covered by snow.
The ABAM/OPHO Association usually has ecotones to Abies amabilis/Tiarella unifoliata and Abies amabilis/Vaccinium alaskaense types. One common pattern involves islands of the Abies amabilis/Tiarella unifoliata Association on raised ground within a matrix of ABAM/OPHO on lower, more poorly drained microrelief. On steeper slopes, ABAM/OPHO forests occur along drainages otherwise within the drier Abies amabilis/Tiarella unifoliata Association. Similar mosaics controlled by microrelief may occur between ABAM/OPHO and drier associations such as Abies amabilis/Vaccinium alaskaense and Abies amabilis/Gaultheria shallon. Within any of these drier forest habitat types, inclusions of ABAM/OPHO forests can be found on wet branches, seeps, or drainages.
The ABAM/OPHO Association is environmentally and floristically related to both the TSHE/OPHO and Abies amabilis/Tiarella unifoliata Associations. Both Oplopanax horridum types are arbitrary divisions of a floristic continuum that extends from lower valleys and drainages to midelevation valleys and wet slopes. The general absence of Oplopanax horridum and several herb species on somewhat drier (and probably warmer) sites serves to distinguish Abies amabilis/Tiarella unifoliata from the ABAM/OPHO Association.
Communities comparable to our ABAM/OPHO type have been described from many other locales in the Cascade Range, British Columbia, and the northern Rocky Mountains. Franklin's (1966) Abies amabilis/Oplopanax horridum association in the southern Washington Cascade Range is essentially identical, as is that described by Brockway et al. (1983). We have sampled a comparable community in the Cedar River drainage, although a Tsuga heterophylla/Vaccinium alaskaense community is the closest approximation reported by del Moral and Long (1977). Closely related communities are common in the North Cascades and in intervening portions of the Mt. Baker-Snoqualmie National Forest. A Chamaecyparis nootkatensis/Oplopanax horridum association appears to be the closest approximation in the Oregon Cascade Range (Dyrness et al. 1974). The closest relative in the northern Rocky Mountains would appear to be the Abies lasiocarpa/Oplopanax horridum Association (Pfister et al. 1977).
Abies amabilis/Tiarella unifoliata Association
The Abies amabilis/Tiarella unifoliata Association (ABAM/TIUN) is herb-rich and occupies mesic mountain slopes at middle elevations. It occurs throughout the Park but is most common in the White and Ohanapecosh River drainages. The elevational range of our 39 sample plots is from 830 to 1490 m (2,740 to 4,920 ft). In the White, Ohanapecosh and Nisqually River drainages, the association often occupies moderate to steep, southerly exposed slopes, sloping benches. and drawswarm but well-watered environments. In the Mowich, Carbon, and North Puyallup River drainages, ABAM/TIUN sites were encountered mostly on steep north-facing slopes above 1200 m (4,000 ft). Despite the contrast in aspect, we found no consistent floristic differences in communities in the two geographic areas; hence we treat them as a single association. Soils are developed in either tephra deposits or colluvium; profiles are deep and well drained, with no evidence of iron-pan development.
Mature forests in the ABAM/TIUN Association are dominated by Abies amabilis, Abies procera, and Tsuga heterophylla (Table 3). Pseudotsuga menziesii is an important associate and can dominate some young stands. There are substantial shifts between the three leading species with stand age. Abies procera is very important in stands up to 400 years of age; we recognized an Abies procera/Tiarella unifoliata community type because of the extent of these distinctive stands. Abies procera is mostly absent from stands older than 400 years which are dominated by Abies amabilis and Tsuga heterophylla instead. About 90 percent of tree reproduction is Abies amabilis in these old stands; saplings are Abies amabilis (77 percent), Tsuga heterophylla (20 percent), and occasional Chamaecyparis nootkatensis (3 percent).
The understory has weak shrub and dense herb layers (average cover 12 and 78 percent, respectively) (Table 4). The major shrubs are Acer circinatum and Vaccinium membranaceum, but Acer circinatum is present in less than half the stands; small amounts of Vaccinium ovalifolium are typically present. Some of the more important herbs are Tiarella unifoliata, Achlys triphylla, Streptopus roseus, Valeriana sitchensis, Rubus lasiococcus, Arnica latifolia, Clintonia uniflora, and Smilacina stellata. Gymnocarpium dryopteris has high coverage in a few stands but is generally absent; the absence or low values for Gymnocarpium, Oplopanax horridum, Rubus spectabilis, and Athyrium filix-femina distinguish this association from the closely related slope variant of the ABAM/OPHO type.
We have already commented on the tendency for Abies procera or Pseudotsuga menziesii or both to dominate young stands. Some of the successional shifts in understory dominants have been reported by Moir et al. (1979).
One of the unique and distinctive features of the ABAM/TIUN Habitat Type is its fine stands of Abies procera (Fig. 17). They are notable on the slopes of Sunrise Ridge (see frontispiece), around Nahunta Falls below the Nisqually River Bridge (easily viewed from the Paradise Valley road east of the river), and on the north side of the Mowich River above Mowich Lake road. It is a productive habitat and capable of rapid recovery following disturbance. Visitors find it attractive for its open, yet luxuriant understories and relatively warm exposures.
The ABAM/TIUN Association is closely related to the Abies amabilis/Rubus lasiococcus and slope phases of the ABAM/OPHO types. ABAM/OPHO often occurs as a stringer and as patches on wetter sites within a matrix of ABAM/TIUN habitats. The ABAM/TIUN Association grades into Abies amabilis/Rubus lasiococcus with elevation, both types tending to occupy southerly mountain slopes. On Sunrise Ridge (frontispiece), the contact between the two associations is quite sharply defined by the shift in dominance from Abies procera to Abies lasiocarpa. Elsewhere, however, the Erythronium montanum phase of the Abies amabilis/Rubus lasiococcus Association can be difficult to distinguish from ABAM/TIUN but is generally poorer in herb cover and species.
Our ABAM/TIUN Association is one element in a series of shrub-poor, herb-dominated Abies amabilis types recognized in the southern Washington and Oregon Cascade Range. Franklin's (1966) Abies amabilis/Streptopus curvipes and Abies amabilis/Tiarella unifoliata associations are closely related to our type at the wet (northwestern) and dry (northeastern) ends, respectively, of the moisture and floristic gradient that it spans in the Park. The Pacific Silver Fir/Coolwort Foamflower Association described for the Gifford Pinchot National Forest (Brockway et al. 1983) is very similar but is slightly poorer in herbs and richer in shrub cover than our association. The Abies amabilis/Streptopus roseus Association of Henderson and Peter (1981) is also similar. In Oregon, Abies amabilis/Tiarella unifoliata and Abies amabilis/Achlys triphylla associations (Dyrness et al. 1974) appear to divide an environmental and floristic gradient on sites similar to our Abies amabilis/Tiarella unifoliata type. In both southern Washington and Oregon, the ABAM/TIUN habitat is where Abies procera attains superior growth and greatest stocking densities. The Abies lasiocarpa/Clintonia uniflora Association of western Montana (Pfister et al. 1977) and Abies lasiocarpa/Pachystima myrsinites Association of northern Idaho (Daubenmire and Daubenmire 1968) are probably the closest northern Rocky Mountain relatives to our ABAM/TIUN.
Modal Forest Ecosystems
Modal forests occupy habitats that lack extreme environmental conditions, i.e., sites excessively wet, dry, cold, or hot. This is, of course, a relative matter considered in the context of the study area. At Mount Rainier the center of the environmental field is occupied by a single, very widespread association, the Abies amabilis/Vaccinium alaskaense (Fig. 11). Characteristics of the tree species are presented in Table 5 and data on the shrub and herb constituents in Table 6.
Abies amabilis/Vaccinium alaskaense Association
The Abies amabilis/Vaccinium alaskaense Association (ABAM/VAAL) is the most extensive of the types found in Mount Rainier National Park. In fact, the mature forests of Tsuga heterophylla, Pseudotsuga menziesii, and Abies amabilis and their associated shrubs and herbs (Fig. 18; see also Plate 1) characterize not only the association but the forests of Mount Rainier as a whole. This association occupies environments lacking extremes of temperature and moisture (see Fig. 11). Nevertheless, the type is widespreadabout 20 percent of all our plots are ABAM/VAAL and the percentage would probably be higher in a random sample. The type also varies substantially, necessitating recognition of several phasesRubus pedatus, Chamaecyparis nootkatensis, and Berberis nervosa. Discussion of these phases follows that of the typical Vaccinium alaskaense phase of the ABAM/VAAL Association.
Vaccinium alaskaense PhaseThe Vaccinium alaskaense phase of the ABAM/VAAL Association generally ranges from 900 to 1330 m (3,000 to 4,390 ft) in elevation, except in the Ohanapecosh drainage where it extends down to 660 m (2,180 ft). It occurs on all aspects on middle and lower slopes and well-drained benches and valley bottom sites; the slopes vary from gentle to moderate (less than 50 percent). The deep, well-drained soils are most commonly podzolic and developed in tephra deposits (for example, see the soil profile for Fryingpan Creek in Chapter 2; see also Fig. 5), although they may also be in alluvial, colluvial, or even laharic parent materials.
Mature forests on the Vaccinium alaskaense phase of this Association are composed of Tsuga heterophylla, Abies amabilis, and Pseudotsuga menziesii, the latter few in number but large in size (Table 5). Thuja Plicata is the only other significant species. Abies amabilis and Tsuga heterophylla dominate the tree reproduction at an average species ratio of 2:1. The Tsuga heterophylla seedlings and saplings have a tendency to decrease with elevation; even at low elevations, however, these seedlings rarely exceed those of Abies amabilis in number or vigor. and they are essentially confined to raised seedbeds (rotten logs, stumps. and rootwads) (Fig. 19).
Understories have well-developed shrub and weak herb layers (average cover 52 and 17 percent, respectively) (Table 6). Vaccinium alaskaense is by far the most important shrub, but Vaccinium ovalifolium, V. membranaceum. V. parvifolium, and Menziesia ferruginea are typically present and can contribute substantial cover in individual stands. The herb layer is composed of a set of evergreen species, each occurring in the majority (but not all) of the plots: Linnaea borealis, Cornus canadensis, Clintonia uniflora, Rubus lasiococcus, R. pedatus, Chimaphila umbellata, C. menziesii, Pyrola secunda, and Goodyera oblongifolia.
A few young stands were sampled. Pseudotsuga menziesii can be a dominant along with Tsuga heterophylla and, to a lesser extent, Abies amabilis. The role of Abies procera is unclear. Few of our stands included Abies procera but this may reflect the fact that most stands were over 400 years old, by which time Abies procera is largely eliminated. Some young stands of the Vaccinium alaskaense phase may be included within the Pseudotsuga menziesii/Viola sempervirens community type.
Berberis nervosa PhaseThe Berberis nervosa phase of the ABAM/VAAL Association was sampled at elevations from 630 to 1220 m (2,080 to 4,080 ft). Plots are mostly on lower slopes or valley bottoms of southerly exposure. The soils are similar to those of the Vaccinium alaskaense phase, namely deep, well-drained soils of tephra and colluvial deposits (Hobson 1976).
Pseudotsuga menziesii and Tsuga heterophylla are codominants of the overstory canopy; Thuja plicata and, less frequently Abies amabilis are minor overstory species (Table 5). As within the Vaccinium alaskaense phase, tree reproduction continues to be dominated by Abies amabilis in the Berberis nervosa phase. Seedling densities of Abies amabilis compared to the second ranked Tsuga heterophylla, have an average ratio of 2:1. Thuja plicata seedlings are also present in most plots but are of low density. The three tree species together account for 98 percent of seedling establishment.
Understories in the Berberis nervosa phase reflect an environment somewhat warmer and drier than that of the Vaccinium alaskaense phase (Table 6). Vaccinium parvifolium and Berberis nervosa join Vaccinium alaskaense as regular and important members of the shrub layer. Taxus brevifolia and Acer circinatum are present in about two-thirds of the plots and are considerably more important than in the Vaccinium alaskaense phase. Vaccinium ovalifolium and Menziesia ferruginea are, on the other hand, less important. Composition of the herb layer of the Berberis nervosa phase differs from the Vaccinium alaskaense phase in poorer representation of Clintonia uniflora and greater coverage of Linnaea borealis.
Rubus pedatus PhaseThis phase of the ABAM/VAAL Association is mostly confined to the Carbon, Mowich, and North Puyallup River drainages. Our plots ranged in elevation from 840 to 1380 m (2,770 to 4,550 ft) and were generally of northerly exposures on lower to upper slopes and benches. Soils developed from deep tephra deposits often had strong iron pan development. These site characteristics suggest that the Rubus pedatus phase represents the ABAM/VAAL type near the cooler and wetter portion of its range.
Tsuga heterophylla and Abies amabilis are almost the only trees present (Table 5). The latter strongly dominates tree reproduction with an average seedling ratio of 11:1 compared to Tsuga heterophylla, Tsuga mertensiana and Chamaecyparis nootkatenisis are both very minor, each contributing only about one percent of the total seedling density.
Shrub dominants in order of importance are Vaccinium alaskaense, V. ovalifolium, V. membranaceum, and Menziesia ferruginea (Table 6). Collectively these provide an average cover of 43 percent. Warm-site shrubs such as Acer circinatum and Berberis nervosa are absent minor. In the herb layer, dominance by Rubus pedatus is one of the distinguishing features of this phase. Other herbaceous differences between the Rubus pedatus and Vaccinium alaskaense phases are the near disappearance of Linnaea borealis and Cornus canadensis from the Rubus pedatus phase, and the greater importance in this phase of Clintonia uniflora and Streptopus roseus. In addition, total herbaceous cover is greater, on the average (27 percent), in the Rubus pedatus phase than it is in the Vaccinium alaskaense phase.
Table 5. Average tree density (stems per hectare) for the modal forest types by species and stem-diameter class, Mount Rainier National Park.
Table 6. Constancy and characteristic cover of all shrub and herb taxa for the modal forest community types of Mount Rainier National Park.
3Average total shrub cover is computed by summing the shrub cover on each plot, then averaging those totals over all plots in a type.
4Average total herb cover is computed by summing the herb cover on each plot, then averaging those totals over all plots in a type.
The Rubus pedatus phase of the ABAM/VAAL has been interpreted in several ways during the development of our classification. It forms a bridge between the Vaccinium alaskaense of the ABAM/VAAL phase and the Abies amabilis/Menziesia ferruginea Association; the Rubus pedatus phase of ABAM/VAAL is closely related to Abies amabilis/Menziesia ferruginea and intergrades with it. The phase is distinctive enough, however, that we gave it full status as a habitat type early in the study (Moir et al. 1979).
Chamaecyparis nootkatensis PhaseThis phase of the ABAM/VAAL Association is based on six plots scattered in various sectors of the Park. Elevations range from 930 to 1360 m (3,070 to 4,490 ft). Most plots occurred on lower slopes of southerly to westerly aspect. Soils varied from a shallow, cobbly-skeletal profile on laharic substrate to more typical, deep, and well-drained tephra soils similar to those of the Vaccinium alaskaense phase.
A distinguishing feature of this phase is the importance of Chamaecyparis nootkatensis (Table 5). This species contributes about 13 percent of the seedlings and saplings, has about equal density in pole-sized trees to Tsuga heterophylla and Abies amabilis, and is second to Tsuga heterophylla in large-sized trees of the overstory canopy (all these statistics being averages). Abies amabilis dominates tree reproduction with 77 percent of seedling density, whereas Tsuga heterophylla is third (after Chamaecyparis) with 9 percent.
The shrub layer is similar to that of the Vaccinium alaskaense phase, namely dominance by Vaccinium alaskaense (33 percent cover) and presence of V. ovalifolium (averaging 9 percent cover), V. membranaceum (6 percent cover), and some minor shrubs (Table 6). The herbaceous layer, however, is usually quite sparse (averaging only about 8 percent cover). The only herbs which exceed 1 to 2 percent cover when present in a stand are Linnaea borealis, Rubus pedatus. and (in one plot) Cornus canadensis.
With so few plots, we were unable to distinguish environments that consistently differ from those of the Vaccinium alaskaense phase. Possibly a greater tendency of fog condensation or other unmeasured environmental feature contributes to the increased importance of Chamaecyparis nootkatensis. Increased snowpack can be speculated as one cause for the general reduction in herb cover.
General Relationships of TypeForests comparable to the ABAM/VAAL Association have been described from many locales in the Cascade Range. Franklin (1966) described an Abies amabilis/Vaccinium alaskaense association as the climatic climax for the Abies amabilis Zone in southern Washington. He also recognized four phases: typical, Berberis nervosa, Berberis nervosa-Xerophyllum tenax, and Xerophyllum tenax. Brockway et al. (1983) describe this association as being, "...Widespread on environmentally moderate sites" in the Gifford Pinchot National Forest. The type apparently occurs as far south as the central Oregon Cascade Range, where a similar Abies amabilis/Vaccinium alaskaense/Cornus canadensis association has been widely recognized (Dyrness et at. 1974, Hemstrom et al. 1982). The Tsuga heterophylla/Vaccinium alaskaense community type of del Moral and Long (1977) appears much broader than our ABAM/VAAL Association, based upon the average coverage of wet-site species (such as Oplopanax horridum) and dry-site species (such as Gaultheria shallon and Berberis nervosa) in their stands.
The ABAM/VAAL Association appears to be also common in the Cascade Range north of Mount Rainier to at least the Mount Baker area (Henderson and Peter 1981, 1985). It appears that there may be a shift toward the Rubus pedatus phase in the northern Washington area, however, and it is possible that our phase is actually the southern representation of the major modal type in the North Cascades. Henderson and Peter (1985) recognized an Abies amabilis/Rubus pedatus Association as distinct from a Rubus pedatus-rich ABAM/VAAL type in the Mount Baker area. The extensive occurrence of a similar type in the Olympic Mountains (Abies amabilis-Tsuga heterophylla of Fonda and Bliss (1969)) also suggests that the Rubus pedatus phase of the ABAM/VAAL Association may predominate at wetter mountain elevations to the north and west of Mount Rainier.
All phases considered together, the ABAM/VAAL Association is related to and forms ecotones with a wide variety of other habitat types. On adjacent warmer and drier slopes, the Abies amabilis/Berberis nervosa or Abies amabilis/Gaultheria shallon Associations may be encountered. At higher elevations, transitions to Abies amabilis/Xerophyllum tenax on upper slopes and ridgetops are found. ABAM/OPHO often forms sharp ecotones with ABAM/OPHO such as in the Ohanapecosh River Valley (East Side trail between Grove of the Patriarchs and Chinook Creek). On slopes, ABAM/VAAL can interface or form mosaics with ABAM/TIUN; the abundance of mesic herbs such as Tiarella unifoliata, Achlys triphylla, and Streptopus roseus and the sparsity of ericaceous shrubs on ABAM/TIUN distinguish it from ABAM/VAAL. Finally, ABAM/VAAL can intergrade to the Abies amabilis/Menziesia ferruginea Association in progressing to cooler environments with increased elevation or northerly exposures.
Abies amabilis/Vaccinium alaskaense is the most extensive association throughout Mount Rainier National Park. Forests may appear somewhat bland and repetitive compared with the lush herbaceous types of wetter environments. They are quite resilient under use, however, and well suited to developments such as campgrounds and trails. A part of the Cougar Rock campground is on the Vaccinium alaskaense phase of the habitat type. In general, the Abies amabilis/Vaccinium alaskaense habitats have few unique attributes (other than commonness) or, fortunately, problems regarding wildlife, visitors, fire, or other phenomena.
Dry Forest Ecosystems
The group of dry forest ecosystems includes four associations and three community types; the Abies amabilis/Xerophyllum tenax could also be considered with the cold group. All three Pseudotsuga menziesii community types are included here for convenience, although one (Pseudotsuga menziesii/Viola sempervirens) is more modal or moist than dry in its characteristics. With that exception, all of the types can be considered to be relatively dry with trees typically suffering at least minor moisture deficiencies every year. The Tsuga heterophylla/Gaultheria shallon and Abies amabilis/Gaultheria shallon probably also suffer from nitrogen deficiencies.
Tree data for the dry group of forest communities are presented in Table 7. Herb and shrub presence and cover are presented in Table 8.
Tsuga heterophylla/Gaultheria shallon Association
The Tsuga heterophylla/Gaultheria shallon Association (TSHE/GASH) characterizes hot, dry slopes and ridges at low elevations. It is most common in the Ohanapecosh and Nisqually River drainages. It is mostly a forest of mountain sideslopes with south to west exposures. Our plots ranged between 550 and 1190 m (1,815 and 3,330 ft) in elevation, Soils are commonly colluvial or well-drained tephras with only weakly developed spodic horizons.
Mature forests are dominated by Pseudotsuga menziesii and Tsuga heterophylla, the former usually more abundant (Table 7). Thuja plicata and occasional specimens of Pitius monticola are less common components of the overstory. The most important reproductive tree is Tsuga heterophylla, but regeneration densities may be very low: stocking of saplings and poles in our plots ranged from 0 to about 220 stems/ha (88/acre). In some stands there were minor amounts of sapling Abies amabilis or Thuja plicata; these were always far less abundant than Tsuga heterophylla.
Table 7. Average tree density (stems per hectare) for the dry forest types by species and stem-diameter class, Mount Rainier National Park.
Table 8. Constancy and characteristic cover of all shrub and herb taxa for the dry forest community types of Mount Rainier National Park.
Acer circinatum may form a conspicuous tall shrub layer (up to 60 percent cover) (Fig. 20), but it can also be minor or absent (Table 8). Other species of this stratum are Taxus brevifolia (1 to 5 percent cover, although one exceptional plot had 60-percent cover) and occasional Amelanchier alnifolia. The lower shrub layer dominated by Gaultheria shallon is a diagnostic feature of this association. Gaultheria shallon cover averages 47 percent (range from 2 to 85 percent). Other rather common shrubs are Berberis nervosa (up to 40-percent cover), Vaccinium parvifolium (1 to 12 percent cover), Vaccinium membranaceum, Rosa gymnocarpa, and Symphoricarpos mollis. Important evergreen herbs of this habitat are Chimaphila umbellata and Linnaea borealis, whereas Xerophyllum tenax occurs in about half of the sample plots. Crown perennials are relatively inconspicuous in the herbaceous stratum, but Achlys triphylla, Festuca occidentalis, Hieracium albiflorum, Listera cordata, Trientalis latifolia, and Pteridium aquilinum are occasional, moderately constant species (appearing in 30 percent or more of the plots).
Pseudotsuga menziesii is a principal seedling or sapling in young stands, but Thuja plicata, Tsuga heterophylla, and Pinus monticola also have moderate to heavy densities. Gaultheria shallon and Pteridium aquilinum averaged 60 and 5 percent cover, respectively, in three stands less than 100 years old.
This association of hot, dry slopes has poor growth rates of tree diameter and height. Many stands, especially in the Ohanapecosh drainage, are even-agedabout 250 years old. Some of these appear relatively stagnant, for succession to the Tsuga heterophylla-dominated climax appears very slow. The TSHE/GASH forests show rather heavy wildlife usage, particularly by browsing deer and elk. Active game trails are conspicuous. Important browse species include Acer circinatum, Vaccinium parvifolium, Amelanchier alnifolia, and saplings of Thuja plicata. Dwarf mistletoe (Arceuthobrium campylopodum) is a major pathogen on Tsuga heterophylla in this and the Abies amabilis/Gaultheria shallon Association.
Mosaics of TSHE/GASH with other forest types are particularly evident near the Ohanapecosh campground and along the Silver Falls trail. Juxtapositions of TSHE/GASH, TSHE/OPHO, TSHE/ACTR, and the Berberis nervosa phase of ABAM/VAAL Associations can all be found. The TSHE/GASH type occurs on the driest microsites. At higher elevations, TSHE/GASH intergrades to the Abies amabilis/Gaultheria shallon Association. Relatively dry midslope environments may have mosaics of TSHE/GASH and Abies amabilis/Berberis nervosa types, the former on slightly hotter or drier microsites.
Comparable ecosystems are widespread in western Washington and Oregon, our type evidently representing an upper-elevational variant. Henderson and Peter (1981) describe TSHE/GASH as the most common association on the White River District of the Snoqualmie National Forest. It has also been identified on the Gifford Pinchot National Forest (Topik et al. 1985), especially "in minor rainshadow areas." In the Cedar River drainage, the Pseudotsuga menziesii/Gaultheria shallon community type of del Moral and Long (1977) apparently occurs on this habitat type. In the Oregon Cascade Range, habitats characterized by Gaultheria shallon typically include Rhododendron macrophyllum as a tall shrub dominant (Dyrness et al. 1974). In the Olympic Mountains. both the Pseudotsuga menziesii-Tsuga heterophylla and Pseudotsuga menziesii types (Fonda and Bliss 1969) appear environmentally and floristically related to our TSHE/GASH Association.
Pseudotsuga menziesii/Ceanothus velutinus Community Type
Extensive areas of young Pseudotsuga menziesii stands 50 to 100 years old occur in the Cowlitz and Ohanapecosh River drainages. Similar stands also occur in other locations in the Park, such as on Crystal Mountain in the White River drainage. It is very difficult to successionally relate many of these youthful communities to the mature associations. These stands have, therefore, been grouped into three Pseudotsuga menziesii types.
The Pseudotsuga menziesii/Ceanothus velutinus (PSME/CEVE) community samples are from two recently burned sites in the Ohanapecosh drainagethe Shriner Burn (last burned in 1934) and an unnamed burn on the north side of Deer Creek. This community occupies moderate to steep, southerly exposed slopes at low to middle elevations. Soils are colluvial and often shallow and stony. The PSME/CEVE type is obviously characteristic of severe (hot and droughty) habitats that have been recently (within the last 100 years) and probably repeatedly burned (Fig. 21).
Pseudotsuga menziesii is the most important tree species (Table 7). Abies procera is important on one plot but is not characteristic. Other tree species include Pinus monticola, Abies amabilis, and Tsuga heterophylla. Basal areas are low in these stands, which are still in a regenerating phase (see Fig. 21).
Understories have moderate densities on the average, although individual sites may be very brushy (Table 8). Acer circinatum, Ceanothus velutinus, and Vaccinium membranaceum provide most of the 33 per cent shrub cover. Shrubs occurring in most plots (80 percent presence or more) are Berberis nervosa, Arctostaphylos uva-ursi, Pachystima myrsinites, Rubus ursinus, and Vaccinium membranaceum. The herb layer is poorly developed but includes many early successional species; Pteridium aquilinum, Epilobium angustifolium, Hieracium albiflorum, and Anaphilis margaritacea all have 100 percent presence.
As mentioned, this community appears to represent early forest development on intensely burned, warm, droughty sites. These sites may represent xeric phases of the Abies amabilis/Berberis nervosa habitat type.
Pseudotsuga menziesii/Xerophyllum tenax Community Type
The Pseudotsuga menziesii/Xerophyllum tenax (PSME/XETE) community occurs throughout the Park. Stands range from 48 to 142 years old. The habitat is found on gentle to moderate, southerly exposed slopes and appears to occupy somewhat less stressful environments than does the PSME/CEVE type. Our plots range widely in elevation, from 800 to 1580 m (2,640 to 5,210 ft). Soils are colluvial, often including substantial tephra.
Pseudotsuga menziesii strongly dominates this community, especially in pole sizes (Table 7). Tsuga heterophylla, Abies amabilis, Pinus monticola, and Abies procera are regular minor associates.
The PSME/XETE community has a substantial understory of both shrubs and herbs (Fig. 22 and Table 8). Important shrubs include Gaultheria ovatifolia, Pachystima myrsinites, Acer circinatum, Vaccinium membranaceum, and Vaccinium parvifolium. Gaultheria shallon and Berberis nervosa have substantial coverage when present. Xerophyllum tenax, which averages 28 percent cover, comprises about half of the herb cover. Other important herbs are Pteridium aquilinum, Linnaea borealis, and Rubus lasiococcus.
The PSME/XETE type is believed to occur mainly on sites assignable to the Abies amabilis/Gaultheria shallon Habitat Type. This is based upon the combination of Gaultheria spp., Xerophyllum tenax. and Acer circinatum as important species. The community may also be successional to the Abies amabilis/Xerophyllum tenax Associationespecially those stands at higher elevations. The Gaultheria spp. suggest that the Abies amabilis/Berberis nervosa association is an unlikely climax to the sere. Nevertheless, the wide elevational span of forests classified in this community type and the different sectors of the Park where it is found lead us to suspect that at least several habitat types may have PSME/XETE communities as seral forests.
Pseudotsuga menziesii/Viola sempervirens Community Type
The Pseudotsuga menziesii/Viola sempervirens Community Type (PSME/VISE) occurs mainly in the Cowlitz, Ohanapecosh, and White River drainages at elevations between 720 and 1280 m (2,380 and 4,220 ft). The ages of trees in our plots ranged from 72 to 153 years. Most stands were on gentle to moderate slopes, on all aspects, and had colluvial and tephra soils (Hobson 1976).
The community type is strongly dominated by pole- and standard-sized Pseudotsuga menziesii (Table 7). This is the most productive of the Pseudotsuga menziesii communities as reflected in basal areas. Associated overstory trees include Abies amabilis, A. procera, Tsuga heterophylla, and Thuja plicata. On the average, the most important seedlings are Tsuga heterophylla and the most important saplings are Abies amabilis, Pseudotsuga menziesii can also be well represented by saplings.
The PSME/VISE type has a dense herbaceous layer (Fig. 23) and highly variable shrub layer (Table 8). Dominant herbs include the pioneer fern, Pteridium aquilinum, found in 90 percent of our plots, and mesic species such as Viola sempervirens, Achlys triphylla, Linnaea borealis, Rubus lasiococcus, and Cornus canadensis. Collectively these herbs contribute about three-fourths of the average herb cover of 54 percent over the 18 sample plots. No shrub species was present in all plots, but the most important shrubs of this community type are Acer circinatum, Berberis nervosa, Vaccinium parvifolium, V. membranaceum, and Gaultheria ovatifolia.
We are uncertain about the successional status of this community type. Stands of the PSME/VISE type are often found adjacent to stands of the ABAM/VAAL Association, occupying the same landform and slope positions. If these forests are successionally related, then Vaccinium alaskaense and its ericaceous shrub associates obviously develop in midsere. On the other hand, the rich herb complement and slope and landform positions of still other stands classified as the PSME/VISE type are also suggestive of the TSHE/ACTR Association.
Abies amabilis/Gaultheria shallon Association
The Abies amabilis/Gaultheria shallon Association (ABAM/GASH) occurs mostly in the western half of the Park, in the Nisqually, Puyallup, and Mowich River drainages. It is typically encountered on moderate to steep, southerly exposed, middle and upper slopes; the mean slope and aspect (51 percent and 194°) of our plots are indicative of a relatively warm, dry environment. Elevational range is from 900 to 1300 m (2,970 to 4,290 ft). Tephra and alluvium are about equally important as soil parent materials.
Tsuga heterophylla and Pseudotsuga menziesii dominate mature stands (Table 7). Thuja plicata and Abies amabilis can be important associates in smaller size classes. Tsuga heterophylla and Abies amabilis are, on the average, of equal importance in reproductive size classes; typically, reproduction of Thuja plicata is also present in small quantities.
Understories of the ABAM/GASH type are strongly dominated by evergreens in the shrub layer and Gaultheria shallon and Xerophyllum tenax in the herb layer (Fig. 24 and Table 8). Other shrubs include evergreen species such as Berberis nervosa and Gaultheria ovatifolia and deciduous Vaccinium parvifolium and Vaccinium alaskaense. Common evergreen herbs, but with minor coverage, are Chimaphila umbellata and Linnaea borealis.
Understory coverage in young communities varies widely from rank to nearly absent, depending upon stand density. Pseudotsuga menziesii is the major seral species, but Tsuga heterophylla can also dominate young stands, especially at higher elevations. Some of the stands included in the PSME/XETE Community Type are probably representative of seral stages on ABAM/GASH habitat type.
Because of low productivity, stands belonging to this association are typically unimpressive. The Tsuga heterophylla are often heavily infected by dwarf mistletoe and the Gaultheria spp. dominated understory is monotonous. On the other hand, the plant cover is resilient and will stand up under heavy use; with the prevalence of tree diseases on this habitat, hazardous trees require special attention.
The ABAM/GASH Association is most clearly related to the TSHE/GASH type, into which it grades at its lower elevational limit, and the Tsuga heterophylla phase of the Abies amabilis/Xerophyllum tenax Association at its upper elevational limits. The abundance of Abies amabilis and Xerophyllum tenax in the ABAM/GASH type differentiates it from TSHE/GASH. The presence of Gaultheria and several other warm-site species differentiates ABAM/GASH from Abies amabilis/Xerophyllum tenax. A third, closely related, dry, slope association is Abies amabilis/Berberis nervosa, although it essentially lacks both Gaultheria shallon and Xerophyllum tenax.
Comparable associations have been described in the southern Washington Cascade Range (Franklin 1966, Brockway et al. 1983) as well as in areas to the north (Henderson and Peter 1981). We have observed comparable types in regions of southeastern Olympic Mountains, Washington, and Fonda and Bliss' (1969) Tsuga heterophylla-Pseudotsuga menziesii type may be related. The Abies amabilis/Rhododendron macrophyllum-Gaultheria shallon Association of the northern Oregon Cascade Range has many similarities (Hemstrom et al. 1982).
Abies amabilis/Berberis nervosa Association
The Abies amabilis/Berberis nervosa Association (ABAM/BENE) is a relatively depauperate habitat type (Fig. 25) that occupies moderately dry, often steep slopes at middle elevations. This type is found most frequently on the east side of the Park with 29 of our 38 plots in the White and Ohanapecosh River drainages. Elevational range is 750 to 1420 m (2,470 to 4,690 ft). Nearly all the plots are on mountain slopes (all positions), which typically exceed 45 percent. Exposures are generally, but not exclusively, southerly. Colluvium and tephra deposits are equally common soil parent materials; shallow stony soils are the usual features of the steep slopes.
Mature forests belonging to the ABAM/BENE Associations are dominated by Pseudotsuga menziesii and Tsuga heterophylla, with Abies procera, Abies amabilis, and Thuja plicata as common associates (Table 7). Seedlings and sapling densities are mainly of Abies amabilis and Tsuga heterophylla with an average ratio of about 1.5:1.
Understories are typically sparse in both shrub (average cover 20 per cent) and herb (average cover 22 percent) layers (see Fig. 25 and Table 8). When present, Berberis nervosa and Acer circinatum provide the only substantial shrub cover, although Vaccinium membranaceum, Vaccinium parvifolium, Pachystima myrsinites, and Rosa gymnocarpa are commonly present. Chimaphila umbellata, Achlys triphylla, and Linnaea borealis are the most important herbs, although others such as Clintonia uniflora, Viola sempervirens, Pyrola secunda, and Rubus lasiococcus are usually present.
Young stands are often dominated by mixtures of Tsuga heterophylla, Pseudotsuga menziesii, Abies procera, and Pinus monticola. Abies amabilis, Thuja plicata, and even Abies lasiocarpa may also be major components of young stands, however. Understories are generally a little richer in young than in old stands.
This habitat type is extensive in the White River drainage. The middle and lower slopes of Shriner Peak and of Sunrise Ridge are largely ABAM/BENE Habitat Type. Much of the habitat type is occupied by stands 50 to 250 years of age, which reflects the greater fire frequency than on ABAM/VAAL habitats (Hemstrom 1982). Young stands are at relatively dynamic stages when extensive mortality can often be expected due to developing competition and subsequent attacks by pathogens. A good example is the extensive destruction of Pinus monticola by bark beetles (Dendroctonus monticolae) along the Sunrise Ridge road during the 1960's. Such waves or episodes of mortality are a natural pattern.
The ABAM/BENE Association is related to the Berberis nervosa phase of ABAM/VAAL and to the ABAM/GASH types. The sparsity of Vaccinium alaskaense and other ericaceous shrubs in mature forests and the warmer, steeper slopes distinguish ABAM/BENE from ABAM/VAAL. At lower elevations, some mature forest stands within ABAM/BENE habitat (for example, plots 30, 407, and 426) have little regeneration of Abies amabilis compared to Tsuga heterophylla. These stands suggest a Tsuga heterophylla phase of this type, but our samples were too few to clearly separate such a phase. Nevertheless, we suspect that at the warmer, drier environments within the ABAM/BENE Association there is gradation, especially in tree regeneration characteristics. to a Tsuga heterophylla/Berberis nervosa Association, which is more widespread outside the Park boundaries (see Fig. 11).
If the ABAM/BENE is primarily an east-side association, its counterpart on the west side of the Park in comparable environments is the ABAM/GASH type. We considered assigning several plots of the ABAM/BENE Association found in the west half of the Park to the ABAM/GASH Association, but their lack of Gaultheria shallon and Xerophyllum tenax made them too distinctive. At any rate, we are uncertain just what subtle shifts in environmental features separate these closely related, but geographically variant associations. Perhaps the distinction between these associations disappears to the south of the Park. Franklin's (1966) Abies amabilis/Berberis nervosa Association includes substantial amounts of both Gaultheria shallon and Xerophyllum tenax but is otherwise similar to the Abies amabilis/Berberis nervosa Association at Mount Rainier. The ABAM/BENE Association of Brockway et al. (1983) on the Gifford Pinchot National Forest is quite similar to ours except that it contains a little more Xerophyllum tenax. An ABAM/BENE type was the second most common association in the Abies amabilis Zone of the White River drainage north of the Park (Henderson and Peter 1981) and extends to the Canadian border (Henderson and Peter 1985). The comparable communities in the Oregon Cascade Range include ABAM/BENE (Hemstrom et al. 1982) and Tsuga heterophylla-Abies amabilis/Rhododendron macrophyllum/Berberis nervosa (Dyrness et at. 1974) Associations.
Abies amabilis/Xerophyllum tenax Association
The Abies amabilis/Xerophyllum tenax Association (ABAM/XETE) is a rather floristically depauperate type found on steep, dry mountain slopes and ridgetops in the upper Abies amabilis and lower Tsuga mertensiana Zones. It is perhaps most extensive in the Nisqually River drainage but can be found throughout the Park. The association is most common at midslope and on upper slopes, and on broad or narrow ridgetops. It occupies any aspect, but southerly exposures are most common. Soils are often stony and of colluvial or tephra deposits. Extremely cobbly, skeletal horizons are usually found at depths between 0.5 and 1 m below the soil surface. Plot 100 in this type has a modal colluvial soil as classified by Hobson (1976) and described in the section on soils (Chapter 2). Elevations of the plots range from 960 to 1610 m (3,730 to 5,310 ft). Two elevational phases reflect the major Tsuga associate: the Tsuga heterophylla phase at lower elevations and T. mertensiana phase at higher elevations. The break between phases generally occurs around 1400 to 1500 m (4,600 to 4,950 ft).
Abies amabilis is the most important species in mature forests (Table 7). Tsuga heterophylla is the major associate in the Tsuga heterophylla phase, but Pseudotsuga menziesii, Abies procera, and Chamaecyparis nootkatensis may also be conspicuous. Tsuga mertensiana and Chamaecyparis nootkatensis are the most important associates in the Tsuga mertensiana phase. Either one or both Tsuga spp. may be important in the transition zone between the two phases (at 1400 to 1500 m or 4,600 to 4,950 ft). About 90 percent of the tree reproduction is Abies amabilis in both phases, with Tsuga heterophylla (in the Tsuga heterophylla phase) and Chamaecyparis nootkatensis making minor contributions.
The forest understory of the ABAM/XETE Association is depauperate (Table 8). The shrub and herb layers appear to be composed almost entirely of Vaccinium membranaceum and Xerophyllum tenax, respectively (Fig. 26). Pyrola secunda, Rubus lasiococcus, and Viola sempervirens are the only other species occurring in over half the plots; their cumulative cover averages only 3 percent. The two phases differ in representation by minor understory species. The Tsuga mertensiana phase consistently has only the five aforementioned species plus low coverage of Rhododendron albiflorum and Clintonia uniflora. Stands of the Tsuga heterophylla phase, on the other hand, are more likely to include small amounts of Berberis nervosa, Chimaphila umbellata, Linnaea borealis, and Vaccinium alaskaense, and less likely to include Rhododendron albiflorum, Clintonia uniflora, or Erythronium montanum.
Young stands can be dominated by any of several tree species; Pseudotsuga menziesii, Pinus monticola, Abies procera, and Abies lasiocarpa are common early successional species. In fact, Pseudotsuga menziesii, Abies procera, and Abies lasiocarpa appear to represent an elevational gradient on slopes from low to high elevations. Abies amabilis, Chamaecyparis nootkatensis, and Tsuga spp. are also important in some young stands. One anomalous young stand containing Abies lasiocarpa and Tsuga mertensiana in regeneration sizes (as well as Abies amabilis and Tsuga heterophylla) occurred on a valley mudflow in the Muddy Fork of the Cowlitz River at the 960 m (3,170 ft) elevation. Perhaps cold air drainage is one of the compensatory features of this low elevation stand. The major floristic feature of the young stands is a much greater average cover of Xerophyllum tenax (49 percent) and Vaccinium membranaceum (21 percent) than that occurring in the mature stands.
This association is frequently encountered by visitors traveling the high forested trails. Its resilient ground vegetation and well-drained soils make it well suited for trails and campsites. Abies amabilis/Xerophyllum tenax habitats (like those of the Abies amabilis/Rubus lasiococcus type) appear to burn more frequently than most other habitat types because of their position on warmer, drier, upper slopes and ridgetops (Hemstrom 1982). Reforestation may be slow and patchy following fire; extensive historical burns can be seen that are still filling in, such as in the upper Stevens Canyon area.
The abundance of Xerophyllum tenax in this association is an important feature. Although most leaves of the plant are consumed in a wildfire, the growing point deep within the clump is protected, and shoot growth resumes almost immediately (Fig. 27). This adaptation to fire is surely responsible for the high coverage of Xerophyllum tenax on burns and in immature stands. Rapid regrowth and extensive root systems make it an important protector against soil erosion and helps retard nutrient leaching during the early years after fire. During years of major flowering, Xerophyllum tenax is not only esthetically important, but the flowering stalks also provide forage for deer and elk. The plant can also be a curse to the cross-country traveler on steep slopes, especially during wet weather when its leaves offer slippery footholds.
At Mount Rainier, the ABAM/XETE Association is most closely related to the Abies amabilis/Rubus lasiococcus and ABAM/GASH types and to the PSME/XETE Community Type. We hypothesize that the Abies amabilis/Rubus lasiococcus occupies somewhat moister environments than does the ABAM/XETE Association. The main features distinguishing the Abies amabilis/Rubus lasiococcus Association are the low coverage or absence of Xerophyllum tenax and an abundance of other herbs. At lower elevations, the Tsuga heterophylla phase of the ABAM/XETE Association appears to grade into the ABAM/GASH type to which it is floristically similar. Abundance of Gaultheria shallon and Berberis nervosa and low coverage of Vaccinium membranaceum distinguish ABAM/GASH from ABAM/XETE Associations. The PSME/XETE Community Type is probably a seral stage of the ABAM/GASH Association at lower elevations and possibly of the ABAM/XETE Association at elevations above about 1200 m (3,950 ft). Nevertheless, at these higher elevations, the successional status of the PSME/XETE Community Type remains unclear. Some stands assigned to this type contain Gaultheria shallon and Acer circinatum, suggesting affinity to the ABAM/GASH Association; whereas other stands lacking substantial coverage of these shrubs appear floristically similar to the ABAM/XETE Association.
Forest communities dominated by Xerophyllum tenax and Vaccinium membranaceum are apparently widespread. The Abies amabilis-Tsuga heterophylla/Vaccinium membranaceum Association of the southern Washington Cascade Range (Franklin 1966) is comparable to the Tsuga heterophylla phase. Franklin's (1966) Abies amabilis-Tsuga mertensiana/Vaccinium membranaceum Association is comparable to the Tsuga mertensiana phase of the ABAM/XETE type. Franklin (1966) used Vaccinium membranaceum to name his types because Xerophyllum tenax is absent from areas of deep, coarse-textured pumice found north and east of Mount St. Helens. The Abies amabilis/Vaccinium membranaceum/Xerophyllum tenax and Tsuga mertensiana/Vaccinium membranaceum Associations from the Gifford Pinchot (Brockway et al. 1983) and Mt. Hood and Willamette National Forests (Hemstrom et al. 1982) are very comparable to the Tsuga heterophylla and Tsuga mertensiana phases, respectively, of our ABAM/XETE Association. The Tsuga heterophylla-Abies amabilis/Xerophyllum tenax Community Type of the Cedar River drainage (del Moral and Long 1977) appears similar to the Tsuga heterophylla phase of our ABAM/XETE but is too rich in coverage of shrubs other than Vaccinium membranaceum to be comfortably assigned to our Tsuga heterophylla phase. An ABAM/XETE Association has been described for the White River drainage (Henderson and Peter 1981) but probably does not occur beyond Snoqualmie Pass. Dyrness et al. (1974) identify comparable communities in the Oregon Cascade Range. They are again separated into two typesAbies amabilis/Vaccinium membranaceum/Xerophyllum tenax and Abies amabilis-Tsuga mertensiana/Xerophyllum tenaxwhich relate to the two Tsuga phases of our ABAM/XETE Association. Subalpine forests of Abies lasiocarpa, Picea engelmannii, and Tsuga mertensiana with Vaccinium membranaceum/Xerophyllum tenax understories are common in the Rocky Mountains of northern Idaho and western Montana (Daubenmire and Daubenmire 1968, Pfister et al. 1977). Comparable communities are apparently absent from the Olympic Mountains and British Columbia (Fonda and Bliss 1969, Krajina 1965).
Cold Forest Ecosystems
The last major group of five associations and one community type occupy relatively cold, snowy environments and are, therefore, most commonly found in the Tsuga mertensiana Zone. These subalpine forests are not exclusively high-elevation types, however; they may occur at moderate elevations (e.g., 1000 m or 3,500 ft) where topography creates areas of cold air drainage or accumulation. Tree data for this group of communities is presented in Table 9. Understory characteristics are presented in Table 10. The reader should recall that several associations discussed earlier (ABAM/XETE and ABAM/TIUN) can also be appropriately considered in this group and are included (for a second time) in Tables 9 and 10 to make comparisons easier.
Abies amabilis/Rubus lasiococcus Association
The Abies amabilis/Rubus lasiococcus Association (ABAM/RULA) encompasses three closely related vegetative types. There are two geographic phases: the wet, west-side Erythronium montanum phase, and the dry, east-side Rubus lasiococcus phase. In addition, a series of early successional stands have been recognized as an Abies lasiocarpa/Valeriana sitchensis Community Type. The Erythronium montanum phase of the ABAM/RULA Association appears to be the most extensive. All three groupings are similar in the sites occupied: at high elevations, often adjacent to meadow or parkland, often southerly exposed, and with modest to well-drained herb layers and a shrub layer largely confined to Vaccinium membranaceum.
Erythronium montanum PhaseThe Erythronium montanum phase is found in the wetter two-thirds of the Park from the Carbon River drainage, counterclockwise through most of the Ohanapecosh River drainage, including the Three Lakes region. Elevations of the 24 sample plots range from 1320 to 1720 m (4,356 to 5,680 ft). Over three-fourths of the plots are on upper slopes or ridgetops, and most have southerly aspects. Soils are generally developed in tephras but range widely in morphology, from little profile development to strong horizonation.
Abies amabilis is the major tree species in mature stands of this association, sometimes forming essentially pure stands (Table 9). Tsuga mertensiana and Chamaecyparis nootkatensis are the most important associates. Abies lasiocarpa or Abies procera may be important in individual stands but not in the type as a whole, The only tree species reproducing in significant numbers is Abies amabilis.
The understory in the Erythronium montanum phase of the ABAM/RULA type is generally distinguished by its herbaceous layer (average cover 40 percent) (Fig. 28 and Table 10). The modest shrub layer (average cover 21 percent) consists mainly of Vaccinium membranaceum although Rhododendron albiflorum is often present in small quantities (up to 10 percent coverage). The herbaceous layer is dominated by Erythronium montanum and Rubus lasiococcus. Other species with high presence are Arnica latifolia, Rubus pedatus, Valeriana sitchensis Viola sempervirens, and Veratrum viride. Understory coverage varies widely and can be quite sparse in stands with dense overstories.
Young stands growing on the Erythronium montanum phase of the ABAM/RULA Habitat Type vary widely in composition and structure. Stands dominated by Abies lasiocarpa and by Abies procera have been encountered along with others dominated by Abies amabilis alone and in mixture with Tsuga mertensiana and Chamaecyparis nootkatensis. Chance probably places a major role in determining tree composition: in other words, seed availability at the time of disturbance. Elevation may play a role in segregating the two seral Abies spp., with Abies procera tending to capture lower elevation and Abies lasiocarpa higher elevation sites in this habitat type.
Table 9. Average tree density (stems per hectare) for the cold forest types by species and stem-diameter class, Mount Rainier National Park.
Table 10. Constancy and characteristic cover of all shrub and herb taxa for the cold forest community types of Mount Rainier National Park.
The Erythronium montanum phase is closely related to the Rubus lasiococcus phase of the ABAM/RULA Association. The Erythronium montanum phase occupies the wetter portions of the Park. The two phases are distinguished by the importance of Erythronium montanum as well as a number of minor shifts in importance and occurrence of other species, but floristic intergradation between the phases is also found in some stands (for example, in plot 490).
Rubus lasiococcus PhaseThe Rubus lasiococcus phase is essentially confined to the White River and northeastern Ohanapecosh River drainages. All but three of the 27 sample plots are on southerly and easterly exposed (aspects 45° to 240°) mountain slopes and ridgetops at elevations of 1270 to 1740 m (4,190 to 5,740 ft). Soils are developed in tephra or colluvial deposits.
Abies amabilis is the major overstory tree species in mature stands but has Chamaecyparis nootkatensis and scattered veteran Pseudotsuga menziesii as major associates (Table 9). Abies amabilis makes up 88 percent of the reproduction, with Chamaecyparis making up most (8 percent) of the remainder.
Herb or shrub layers are not well developed in mature stands in the Rubus lasiococcus phase (Table 10). The shrub cover (average 30 percent) is strongly dominated by Vaccinium membranaceum. The herbaceous layer (average cover 21 percent) has Rubus lasiococcus, Pyrola secunda, Arnica latifolia, Valeriana sitchensis, and Clintonia uniflora as the most important components. Erythronium montanum is absent or has cover not over 2 percent (plot 490 is an intergrade phase whose herb complement is dominated by both Erythronium montanum and Rubus lasiococcus).
Many young stands of the Rubus lasiococcus phase, particularly at higher elevations, are dominated by Abies lasiocarpa. We assigned most of these stands to the Abies lasiocarpa/Valeriana sitchensis community type. At lower elevations within this phase, young stands may be dominated or codominated by Abies procera. In both this and the Erythronium montanum phase, herbaceous cover tends to be greater in young than in mature stands.
Other associations closely related to both phases of the Abies amabilis/Rubus lasiococcus are the ABAM/TIUN, ABAM/XETE, and Abies amabilis/Rhododendron albiflorum. At the boundary of its lower elevation the ABAM/RULA type grades into the strongly herb-dominated ABAM/TIUN type. Modal forests of these two types are easily distinguished. There is, for example, a much more diverse and luxuriant herb layer, general absence of Erythronium, and replacement of Tsuga mertensiana by Tsuga heterophylla in ABAM/TIUN stands, as well as a sparsity of Tiarella unifoliata on the ABAM/RULA type. Floristic and environmental intergrades occur between the two associations and may make a site difficult to classify, however. The Abies amabilis/Rhododendron albiflorum type has a shrub layer that is much denser and richer in species than occurs on the Erythronium montanum phase of the ABAM/RULA Association. The ABAM/XETE Association is distinguished from ABAM/RULA by the dominance of Xerophyllum tenax and sparsity of other herbs. Only 2 stands of 50 in the ABAM/RULA Association had Xerophyllum cover of over 6 percent. The ABAM/XETE sites are warmer and drier than those of ABAM/RULA, which are, in turn, warmer and drier than those of the Abies amabilis/Rhododendron albiflorum and Abies amabilis/Menziesia ferruginea habitat types.
This habitat type presents no major management problems. The forests are attractive to visitors because they occupy warmer exposures and lack the heavy shrub cover and saturated soils of the north slope and bench forests within the Tsuga mertensiana Zone.
Franklin's (1966) Abies amabilis/Veratrum viride Association of the southern Washington and northern Oregon Cascade Range is similar to our ABAM/RULA type. Most of Franklin's plots were actually in seral Abies lasiocarpa stands assignable to the Abies lasiocarpa/Valeriana sitchensis Community Type, however. The Abies amabilis/Vaccinium membranaceum/Clintonia uniflora Associations from the Gifford Pinchot, Mt. Hood, and Willamette National Forests appear closely related (Brockway et al. 1983, Hemstrom et al. 1982). The relationships between our ABAM/RULA Association and types to the north of the Park are currently confused. In his work on the Mt. Baker-Snoqualmie National Forest, Henderson (see, e.g., Henderson and Peter 1981) created Tsuga mertensiana/Vaccinium membranaceum and Abies amabilis/Vaccinium membranaceum Associations which include elements of our ABAM/RULA type, but thorough comparisons must await availability of detailed stand data. Fonda and Bliss' (1969) Abies amabilis-Tsuga mertensiana type appears to be an Olympic Mountain relative of the Erythronium montanum phase.
Abies lasiocarpa/Valeriana sitchensis Community Type
Pure or nearly pure Abies lasiocarpa forests dominate warm, southerly slopes at high elevations in the White and Ohanapecosh River drainages. These young stands (often 100-200 years old) are similar in structure and composition and distinctive enough to be distinguished as the Abies lasiocarpa/Valeriana sitchensis Community Type (ABLA2/VASI). We interpret this community type as an early vegetation stage within environments of the ABAM/RULA Habitat Type.
The elevations of the 21 stands sampled in this community ranged from 1450 to 1860 m (4,780 to 6,140 ft), with the aspects generally southerly (average 187° ranging from 112 to 308°) The topography often consisted of upper slopes or ridges, and the soils consisted of tephra and colluvial parent materials.
Abies lasiocarpa dominates this community (Fig. 29); Pseudotsuga menziesii and Abies amabilis are the most consistent associates, although Abies procera, Tsuga mertensiana, and Picea engelmannii can all be important in individual stands (Table 9). Abies amabilis invariably dominates the seedling and, generally, the sapling size classes as well; we hypothesize the gradual replacement of Abies lasiocarpa by Abies amabilis as the forests mature.
The understory has a luxuriant layer of herbs (average cover 65 percent) and a modest shrub layer (average cover 24 percent) composed mainly of Vaccinium membranaceum (Table 10); Vaccinium scoparium or V. deliciosum or both also appear in most stands. Major herbs are Rubus lasiococcus, Valeriana sitchensis, Arnica latifolia, Viola sempervirens, Polemonium pulcherrimum, two species of Luzula, Veratrum viride, Mitella spp., Viola glabella, Clintonia uniflora, and Pedicularis racemosa. This community is often adjacent to meadows, and understories reflect this influence with frequent occurrence of species such as Senecio triangularis and Ligusticum grayi.
The ABLA2/VASI type is an attractive and important community type on Sunrise Ridge, at Grand Park, and along the crest of the Cascade Range. It occupies much of the forest-parkland ecotone in these areas, making it important to visitors and wildlife. Fire danger in this type is among the highest of any in the Park (Hemstrom 1982) because of the frequency of lightning strikes, its location in the driest part of the Park, and abundance of continuous highly flammable fuels represented by the limby, resinous Abies lasiocarpa. It is only moderately resilient to visitor impacts but may be suitable for back-country camp sites.
This community type has strong affinities with the many Abies lasiocarpa communities found along the east slope of the Cascade Range and in the northern Rocky Mountains (Pfister et al. 1977). At Mount Rainier, Abies lasiocarpa is usually subject to replacement by Abies amabilis, making the community type seral (Franklin and Mitchell 1967). Franklin (1966) noted similar stands as far south as the east slopes of Mount Hood (see his Abies amabilis/Veratrum viride Association). Thornburgh (1969) noted that Abies lasiocarpa dominated stands on high south slopes near the southwest corner of Mount Rainier (High Rock). Stands of the ABLA2/VASI Community Type do occur on the west side of the Park, within the Erythronium montanum phase of the ABAM/RULA Habitat Type, but are less common than on the east side. This could be due to a variety of factors, including less frequent fires and greater competition from associated species on the moister west side. We have noted comparable stands in the Glacier Peak and Goat Rocks Wilderness areas. Fonda and Bliss (1969) describe similar stands in the northeast corner of Olympic National Park.
Abies amabilis/Menziesia ferruginea Association
The Abies amabilis/Menziesia ferruginea Association (ABAM/MEFE) is a common, shrub-dominated, midelevation to high elevation type found throughout Mount Rainier National Park. It occupies relatively cool, moist sites in the upper Abies amabilis and lower Tsuga mertensiana Zones where snowpacks are moderate to heavy. All aspects and landforms are represented in the 27 sample plots, although northerly aspects and mountain slopes and benches are the most common sites. Plot elevations range from 1080 to 1500 m (3,560 to 4,950 ft). Tephra soils with minimal or weak iron-pan development are most common.
Mature forests are dominated by Abies amabilis, which also makes up 88 percent of the seedlings and 70 percent of the saplings (Table 9). Either Tsuga mertensiana or Tsuga heterophylla can be the major hemlock associate, although the latter is the most abundant and both are often present. Chamaecyparis nootkatensis is present in about 75 percent of the plots and can be an important dominant. All other tree species are minor.
The understory generally has a well-developed shrub layer (Fig. 30) (average cover 44 percent) and a modest herb layer (average cover 16 percent) (Table 10). Major shrubs are, in order of appearance, Menziesia ferruginea, Vaccinium membranaceum, V. ovalifolium, V. alaskaense, and Rhododendron albiflorum (Table 9). The most important herbaceous species are Rubus pedatus, R. lasiococcus, Xerophyllum tenax, Pyrola secunda, Clintonia uniflora, and Streptopus roseus. Average cover is low for all six species (less than 4 percent). Only Rubus lasiococcus has high presence, occurring in more than 90 percent of the stands. Erythronium montanum has low presence but may be abundant when it does occur (up to 10 percent cover).
Seven young forests were analyzed separately. Tree diversity is much greater in young than in old stands (Table 9). Abies amabilis and Tsuga heterophylla are still dominant, but Abies lasiocarpa, Abies procera, Pseudotsuga menziesii, and Thuja plicata all share the role of major associates in one or more stands with Tsuga mertensiana and Chamaecyparis nootkatensis. Shrub cover (average 81 percent) is much greater in young than in mature stands. The five shrub species listed for mature stands are still dominants, but Alnus sinuata is an important addition in some stands. Differences in the herb layer appear minor except for the addition of Pteridium aquilinum.
Its extent makes the ABAM/MEFE an important association within the Park. It is indicative of moderate snowpack levels and moist but not waterlogged sites; hence, management constraints are fewer than on the environmentally more severe Abies amabilis/Rhododendron albiflorum sites. The ABAM/MEFE type is not the best choice for site development, however, tn terms of length of growing season and soil drainage. although the vegetation is typically dense and resilient.
Both the Abies amabilis/Rhododendron albiflorum and ABAM/VAAL Associations are closely related to the ABAM/MEFE type. There is a much greater abundance of Rhododendron albiflorum and Chamaecyparis nootkatensis in the Abies amabilis/Rhododendron albiflorum than in the ABAM/MEFE type. The regular occurrence of Tsuga heterophylla in the ABAM/MEFE Association is a feature that suggests more favorable temperatures and snowpack than in the Abies amabilis/Rhododendron albiflorum Association. The ABAM/MEFE can be distinguished from the ABAM/VAAL type by a variety of features including the regular occurrence of Tsuga mertensiana, Chamaecyparis nootkatensis, and Menziesia ferruginea and sparsity of many ABAM/VAAL indicators such as Pseudotsuga menziesii, Cornus canadensis, and even Vaccinium alaskaense.
Similar associations have been reported from adjacent portions of the Cascade Range. Franklin (1966) recognized an Abies amabilis/Menziesia ferruginea Association in the southern Washington Cascade Range. Floristically this association is very similar to ours. Mountain hemlock is more common than western hemlock in Franklin's type, although "... this is the only association where extensive mixing of the two hemlocks was encountered...," a situation comparable to the ABAM/MEFE type at Mount Rainier. He also considered this type to be at the transition between the Tsuga mertensiana and Abies amabilis zones. The Abies amabilis/Menziesia ferruginea Association described for the Gifford Pinchot (Brockway et al. 1983) and Mt. Hood and Willamette (Hemstrom et al. 1982) National Forests are very similar to our association. Chamaecyparis nootkatensis and Rhododendron albiflorum are generally important and herbs are generally of lesser importance at Mount Rainier than in associations to the south. The relationship between our ABAM/MEFE Association and communities to the north is currently confused. Although Henderson and Peter (1981) report an ABAM/MEFE Association in the White River drainage, it was not common and is not reported from more northerly locales (see, e.g., Henderson and Peter 1985). The type may either be absent or have been partitioned into other associations. The Abies amabilis-Tsuga heterophylla/Vaccinium membranaceum and Abies amabilis/Vaccinium membranaceum-Vaccinium ovalifolium community types described by del Moral and Long (1977) from the Cedar River drainage have similarities to our ABAM/MEFE, although it is difficult to tell from the data presented; their two community types were separated primarily by the abundance of Tsuga heterophylla, a characteristic which we view as being of minor importance on this habitat type.
Similar subalpine forest communities, minus Abies amabilis, have been described from the northern Rocky Mountains. The Tsuga mertensiana/Menziesia ferruginea and Abies lasiocarpa habitat types of Daubenmire and Daubenmire (1968) and of Pfister et al. (1977) are the best examples.
Chamaecyparis nootkatensis/Vaccinium ovalifolium Association
The Chamaecyparis nootkatensis/Vaccinium ovalifolium Association (CHNO/VAOV) occurs on wet, often nearly swampy sites in the upper Abies amabilis and lower Tsuga mertensiana Zones throughout the Park. Wet benches, draws, and lower slopes are typical landforms occupied by this relatively uncommon habitat type. Elevational range of the 15 sample plots is from 1170 to 1470 m (3,860 to 4,850 ft). The type can occur on any aspect, although most plots have northerly aspects. Soils develop in parent materials of tephra, alluvium, and colluvium. Deep organic surface horizons, high water tables, gleyed sub-soils, and strong iron pans are common.
Chamaecyparis nootkatensis and Abies amabilis dominate mature forests, with Tsuga mertensiana, Tsuga heterophylla, or both as important associates (Table 9). Picea engelmannii may be present where cold air flows down valley drainages. Abies amabilis dominates the reproduction and is apparently the major climax tree species. Reproduction of Chamaecyparis nootkatensis is also abundant, however, with numbers approaching those of Abies amabilis in a few cases; this suggests that Chamaecyparis nootkatensis will also be at least a minor climax species. In fact, its maximum occurrence in the Park is on CHNO/VAOV habitats, based on abundance in all size classes and on total basal area.
The understory has a relatively rich and luxuriant herbaceous layer (Table 10). Shrub cover averages 39 percent but has a wide range of 10 to 65 percent. Major shrubs are Vaccinium ovalifolium, Menziesia ferruginea, Vaccinium membranaceum, and Rhododendron albiflorum. The distinctive compositional features are in the herb layer (average cover 59 percent). Typical dominants occurring in over half the plots are Rubus pedatus, Rubus lasiococcus, Tiarella unifoliata, Streptopus roseus, Viola glabella, Erythronium montanum Valeriana sitchensis, Gymnocarpium dryopteris, and Clintonia uniflora. The nearly swampy nature of this association is even more sharply characterized by several "wetland" species which have, however, relatively low presence and importance values: Mitella spp., Trautvetteria caroliniensis, Parnassia fimbriata, and Stenanthium occidentale are good examples.
No young stands were sampled on this habitat type. Immature stands should closely resemble mature stands in composition, however. Shrub cover would be relatively high in early successional stages and would include species such as Salix scouleriana and Alnus sinuata. Forest stand development might be slow due to heavy competition from herbs and shrubs.
Special features of this association include the diversity of wetland species and maximal densities of Chamaecyparis nootkatensis as a forest component. It is obviously a poor environment for trails and totally unsuited for development of campsites. The wet soils and numerous springs, seeps, and streams would make trail construction expensive and maintenance a continuous problem. This habitat type is often associated with natural openings (wet meadows, fens, bogs, and ponds). Shrub thickets of Alnus sinuata, Salix spp., and Spirea spp. often occur at these ecotones between forest and fen. The association of this habitat type with streams, ponds, and springs makes it rich in wildlifebirds, mammals, and especially amphibians.
The most clearly related habitat types in the Park are Abies amabilis/Rhododendron albiflorum and ABAM/OPHO. The former is generally on slopes at higher elevations, has much heavier shrub cover in which Rhododendron albiflorum is always present, and has a less diverse, less prolific herbaceous layer. The Abies amabilis/Rhododendron albiflorum Association probably experiences deeper snowpacks and colder temperatures than the CHNO/VAOV type, although frequent cold air accumulations are to be expected in the benches and terraces occupied by the CHNO/VAOV Association. The abundance of Chamaecyparis nootkatensis, Vaccinium spp.-dominated shrub layer, and general absence or sparsity of several key indicator species (for example, Oplopanax horridum, Athyrium filix-femina, and Ribes lacustre) distinguish CHNO/VAOV from the ABAM/OPHO Associations. Both air and soil drainage appear more rapid on ABAM/OPHO than CHNO/VAOV habitats, and productivity is correspondingly greater due to warmer temperatures and more aerobic soil environments.
Forest communities similar to the CHNO/VAOV Association have not been described from other parts of the Pacific Northwest. If the area of this habitat type is as limited in other locales as it is at Mount Rainier, other plant ecologists may have encountered it but chose to ignore it or treat it as an ecotone or minor edaphic type.
Abies amabilis/Rhododendron albiflorum Association
The Abies amabilis/Rhododendron albiflorum Association (ABAM/RHAL) is a shrubby, high-elevation environment of cool, wet slopes and benches found throughout the Park. Many stands occupy northerly aspects, although the type also occurs on some wet southerly aspects. Plot elevations range from 1210 to 1730 m (4,000 to 5,710 ft). Soils are generally podzolic with gleyed subsoils and iron pans, indicating high water tables and saturated conditions for most of the year. The association occupies a very cold and wet forest environment with a heavy snowpack (5 m or more) that lasts well into the summer; the growing season is, consequently, very short.
Mature forests are characteristically codominated by Abies amabilis, Tsuga mertensiana, and Chamaecyparis nootkatensis (Table 9). Tsuga heterophylla, Pseudotsuga menziesii, Abies procera, and Pinus monticola may occur but are minor components. Tree reproduction is strongly dominated by Abies amabilis with over 1,500 seedlings and saplings per hectare (600/acre). Abies amabilis constitutes 87 percent of the tree reproduction, with Chamaecyparis nootkatensis at 8 percent and Tsuga mertensiana at 4 percent.
The understory is a dense tangle of shrubs (Fig. 31) (total cover 72 percent) with scattered herbs (total cover 31 percent) (Table 10). Rhododendron albiflorum, Vaccinium membranaceum, Vaccinium ovalifolium, and Menziesia ferruginea are the constant shrub dominants and cumulatively provide 90 percent of the shrub cover. Three common herbs (Erythronium montanum, Rubus lasiococcus, and Rubus pedatus) provide about 80 percent of the herbaceous cover. Some of the occasional minor herbs include Listera caurina, Pyrola secunda, Xerophyllum tenax, Achlys triphylla, and Clintonia uniflora.
The few young stands sampled on this habitat type closely resemble the mature stands floristically. Shrub cover is typically very high until tree canopies close, and this may take a century or more due to low reproductive success. Shrub competition and the severe environment, with a very heavy, persistent snowpack, are both major deterrents to tree reproduction.
The key management aspects of this habitat type relate to its severe environmenta heavy, persistent snowpack; short, cool growing season; and soils with high water tables. Productivity is limited, trees do not attain large sizes, and, as indicated, new stands develop slowly following disturbance. Managers should avoid putting developments, including trails and back-country campsites, in this habitat type when ever possible.
The relationship between the ABAM/RHAL and ABAM/MEFE Associations is so strong that we considered making both part of a somewhat broader, high elevation association. The former occupies, on the average, higher elevations and admits less Tsuga heterophylla and more Tsuga mertensiana in the tree complement. Reasons for the shift in dominance between Rhododendron albiflorum and Menziesia ferruginea in these two associations are not clear. In addition, several stands on the undulating topography of higher elevations in the Park are not easily assignable to one or the other of these associations. Until high-elevation forest ecology in the Park is studied further, however, we prefer to hypothesize the distinctness of the ABAM/RHAL and ABAM/MEFE Associations.
The ABAM/RHAL and CHNO/VAOV Associations are obviously closely related environmentally. CHNO/VAOV occupies sites that are wetter and colder (by cold air convection) than the ABAM/RHAL.
Forests similar to ABAM/RHAL have been reported from adjacent portions of the Washington Cascade Range. Franklin's (1966) Chamaecyparis nootkatensis/Rhododendron albiflorum association is very similar, as are the Tsuga mertensiana/Rhododendron albiflorum (Brockway et al. 1983) and Abies amabilis/Rhododendron albiflorum/Clintonia uniflora (Hemstrom et al. 1982) Associations. Henderson and Peter (1981) refer to their White River association as the Tsuga mertensiana/Rhododendron albiflorum type; it appears to become more varied in the northern Cascades (Henderson and Peter 1985). The use of three tree species in these association's names reflects varying preferences among the reproducing (and presumably climax) tree species.
Other Forest Communities
Several other forest types at Mount Rainier represent very specialized habitats of limited extent. Examples include; pioneering forest stands invading recently exposed glacial till, river alluvium, or lahar surfaces; talus slopes with a scattered forest cover; and swamp forests.
Pseudotsuga menziesii/Arctostaphylos uva-ursi Association
The Pseudotsuga menziesii/Arctostaphylos uva-ursi Association (PSME/ARUV) is extremely limited at Mount Rainier. Only two stands were sampledon an outwash along the White River (Plate 1) and on a lahar surface near the west end of the Longmire campground. Alone, these two stands would be insufficient for recognizing an association; however, similar communities have been described (Franklin 1966) on lava flows, glacial outwash, and young pyroclastic flows in southern Washington and northern Oregon.
Stands in PSME/ARUV habitats are open, low in stature, and distinctive in composition (Fig. 32). Either Pseudotsuga menziesii or Pinus contorta may dominate, but almost any other indigenous tree species can be present provided a seed source is available. For example, both Abies lasiocarpa and Chamaecyparis nootkatensis occur in the Longmire stand, which is at about 800 m (2,640 ft).
The understory is low in stature but distinctive in composition. Major vascular plants are Juniperis communis and Arctostaphylos uva-ursi. There is a nearly complete ground cover of mosses and lichens in which Rhacomitrium canescens var. ericoides is the major component.
The vegetation on these sites is very hardy and, with the exception of the moss and lichen ground cover, will tolerate heavy use. Root systems are well protected by the rocky surface. Tree growth is very slow, and continuing mortality is apparent in the stands. These are interesting sites because of the high diversity of tree species often present and the distinctive ground plants.
As mentioned, similar forests have been described from a variety of substrates in the southern Washington and northern Oregon Cascade Range. Pinus contorta is probably the most common tree dominant, but Pseudotsuga menziesii is typically present and may be a climax species.
Swamp forests are open stands of stunted conifers or hardwoods occurring in localized wetlands (Fig. 33). Such sites are not extensive and often occur as ecotones between forests and marshes or ponds. At low to moderate elevations, Thuja plicata, Pinus monticola, Tsuga heterophylla, and Alnus rubra are the species most likely to be associated with wetlands. The scattered trees are typically associated with Lysichitum americanum, Carex spp. (especially Carex obnupta), and ferns as herbaceous dominants. Lysichitum and other wetland herbs may also occur in small stands within a forest matrix on seasonally ponded habitats. Shrub associates on the wetlands include Salix spp., Spiraea spp., and Alnus sinuata. Swamps at higher elevations are similar but have Chamaecyparis nootkatensis, Tsuga mertensiana, Pinus monticola, Picea engelmannii, and Abies amabilis as constituent tree species.
Moraine forests have been studied by Sigafoos and Hendricks (1972) for the purpose of dating glacial activities. Our plots 350 and 484 occur on morainal debris of the Tahoma and Emmons glaciers. Soils of these cobbly rubbles are undeveloped. Sapling or pole-sized trees, often as thickets, include Abies amabilis, A. lasiocarpa, Tsuga heterophylla, T. mertensiana, andparticularly on the Emmons morainePinus contorta and Picea engelmannii. The common shrub is Alnus sinuata, and herbs are almost nonexistent. Moraine forests are particularly conspicuous at Moraine Park. Here tree thickets thrive on lateral moraines of the Carbon Glacier with herbaceous meadows on fine-textured soils of the intermorainal landscape.
Additional Forest Types
Pinus albicaulis sometimes fringes forests at timberline. More often this species occupies a seral role in subalpine parklands (Franklin and Mitchell 1967). An interesting dwarf forest of Pinus albicaulis with Juniperis communis can be found on the high, rocky ridges above Yakima Park.
We found a variety of additional unusual forests which we were unable to classify. Several of these (for example, plots 348 and 433) were essentially riparian forests exhibiting unusual combinations of tree and understory dominants. Populus trichocarpa is a conspicuous dominant of old river bars; perhaps further sampling would have clarified the vegetational composition of this community type. At least one of our plots (356) was classified as a Tsuga heterophylla/Oplopanax horridum association, but another containing both Populus trichocarpa and Abies grandis (plot 433 along the White River) was too unusual to be classified into any of the major associations or community types.
An all-aged Pseudotsuga menziesii forest on cobbly-skeletal soil occurs just outside the East Park boundary (Plot 292). We feel it is related to the Pseudotsuga menziesii/Holodiscus discolor Association (Dyrness et al. 1974), but have no further plots in the Mount Rainier area for comparison or grouping.
Several mature forest stands contained extremely sparse, vascular plant understories but conspicuous moss cover on the forest floor. Perhaps mossy forest community types or associations exist in the Park, especially on certain riparian sites or on cobbly or skeletal valley bottom soils. Our plots 34 and 205 are examples of mature mossy forests. These should not be confused, however, with shaded stages of immature forests on a variety of other habitat types in which mosses are also the most conspicuous understory layer.
Finally, we have a small residue of plots unclassified because they represent very young, early seral forests giving little hint to which, if any, of the associations or community types they are related. Several of these plots occurred on the 1947 Kautz mudflow, and another was a 48-year-old stand in the Golden Lakes area (just across a fireline from an older forest of the Erythronium montanum phase of Abies amabilis/Rubus lasiococcus association).
Last Updated: 06-Mar-2007