MOUNT RAINIER The Forest Communities of Mount Rainier National Park

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.

Figure 11. Generalized distribution of habitat types in relation to an idealized two-dimensional environmental field. The horizontal axis represents a moisture gradient and the vertical axis a temperature gradient that is correlated to elevation and forest zones. Because the moisture span may not be as broad at high elevations as it is at low, the rectangular shape of the environmental field is merely for visual convenience (see Fig. 34 for detailed example). Diagonal boundaries between habitat types suggest general effects of slope; for example, the warm, dry environment of a habitat type may be found at higher elevations on southerly slopes, and cool, wet environment of a habitat type at lower elevations on northerly slopes. Minor forest types are not shown except for localized swamp forests on wettest sites at low and intermediate elevations. The Tsuga heterophylla/Berberis nervosa and Pseudotsuga menziesii/Holodiscus discolor habitat types have not been found within the Park but occur on adjacent forest lands. Abbreviations are defined on the inside front cover.

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.

Figure 12. Mature 250-year-old Pseudotsuga menziesii forest in Tsuga heterophylla/Achlys triphylla habitat type; the herbaceous understory is unusually dense in this stand located near the Ohanapecosh Ranger Station.

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.

Figure 13. High densities of large trees are characteristic of mature stands in the Tsuga heterophylla/Polystichum munitum habitat type. Pseudotsuga menziesii and Thuja plicata are visible in this stand along the Chenuis Falls trail.

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.

Figure 14. Luxuriant herbaceous understories are typical of forests comprising the Tsuga heterophylla/Oplopanax horridum habitat type, although substantial shifts in the herb dominants take place within and between stands.

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.

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²Unpublished report, "Phytosociological reconnaissance of western redcedar stands in four valleys of the North Cascades Park Complex," by Joseph W. Miller and Margaret M. Miller. 50 p. Dec. 1970. On file at Forestry Sciences Laboratory, Corvallis, Oregon.

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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 codominant—depending 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).

Figure 15. The Alnus rubra/Rubus spectabilis community type is a seral community occurring on the Tsuga heterophylla/Oplopanax horridum and Abies amabilis/Oplopanax horridum habitat types; Alnus rubra dominates the tree layer, and there is a dense shrubby understory which is a favorite habitat for elk. In this stand along Tahoma Creek. Oplopanax horridum is conspicuous in the understory.

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.

Figure 16. This stand in the Abies amabilis/Oplopanax horridum habitat type has a very dense layer of Oplopanax horridum; a well-developed herb layer is also present. Along lower Chinook Creek.

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 draws—warm 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.

Figure 17. Outstanding examples of Abies procera are common on Abies amabilis/Tiarella unifoliata habitat type.

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 widespread—about 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 phases—Rubus pedatus, Chamaecyparis nootkatensis, and Berberis nervosa. Discussion of these phases follows that of the typical Vaccinium alaskaense phase of the ABAM/VAAL Association.

Figure 18. Mature forests of Abies amabilis, Tsuga heterophylla, and Pseudotsuga menziesii characterize the very widespread Abies amabilis/Vaccinium alaskaense habitat type. This type occupies modal environments, can be considered the climatic climax of the Abies amabilis zone, and is the forest archetype for Mount Rainier National Park.

Vaccinium alaskaense Phase—The 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).

Figure 19. Tsuga heterophylla reproduction in the Abies amabilis/Vaccinium alaskaense habitat type is essentially confined to rotten logs and other raised seedbeds; this is true in most other associations as well.

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 Phase—The 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 Phase—This 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.

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 Phase—This 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 Type—Forests 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.