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Forest (森林)

Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

One of the biomes (バイオーム) that has a dense growth of trees, plants and underbrush covering a large area, but..., how dense?
An ecosystem or assemblage of ecosystems dominated by trees and other woody vegetation, ... still, but how dominated?

physiognomy (相観)

Defined by the US National Vegetation Classification System

consisting of trees with overlapping crowns forming 60% to 100% cover
Opened with 25% to 60% cover

[ mixed forest | Cascades | Alaska ] [ Jomon forest ]


Forest type (森林型)

On the global scale, forest types are classifed by temperature and precipitation. However, classification systems are not unified.

Tropical forest (熱帯林) 4 Boreal forest
forestThe background of plantation for conducting agroforestry is a natural rainforest at Los Banos. Philippines. The dominant species are tall, evergreen broad-leaved trees. When precipitation decreases, the forest changes to seasonal forest. forestIt is often the same with deciduous (borad-leaved) forest. Check tree species in Hokkaido, Japan. In Hokkaido, mixed forest with evergreen needle-leaved and decidous broad-leaved trees is also found. forestBoreal forest is taiga, or includes southerly part of taiga. Taiga is characterized by needle-leaved trees, such as Picea mariana in Alaska and Larix gmelinii in eastern Siberia. Permafrost is related to the distribution patterns of taiga. (Photo: a wildfire occurring in P. mariana forest)

Tropical forest

Distribution of tropical forests in the world
Persebaran Kawasan Hutan Tropis di Dunia
tropical forest

Subropical forest

Temperate forest

Laurentian mixed forest (ローレンシアン混交林)
= North Woods (one of the forest ecoregions)
temperate broadleaved and mixed forests biome transition zone between the boreal forest and the Big Woods and Carolinian forest

Conifers: pines, spruces, firs and junipers
Deciduous trees: aspens, paper birches mountain ash and maples

distributed in eastern North America

most of the region was covered by glaciers during the last ice age

Boreal forest (冷温帯林)

Fig. Vegetation change in Siberian taiga
Timber line: boundary of forest and forest-less zones
Tree line: boundary of tree and tree-less zones = similar with Japanese subalpine zone
Altitudinal vegetation zonation patterns are similar with latitudinal patterns → the causes of differences in vegetation between them

Mixed forest (針広混交森林)

Mixed forest or boreo-nemoral transitional forest

The forest develops tween temperate broad-leaved and subarctic needle-leaved forests.

Forest zoneBoreal coniferous (taiga)Boreonemoral-mixedNemoral-temperate summer green
Needle-leaved treesPicea, Abies, Pinus, Tsuga, etc.Picea, Abies, Pinus
Broad-leaved treesQuercus, AcerFagus, Acer, Quercus, Tilia

Mixed1 Mixed2
[1/2] between Jozankei and Nakayama Pass, Sapporo, on October 9 2010. The red and yellow leaves are from deciduous broad-leaved trees, and the green leaves are from evergreen needle-leaved trees.

Forest classification for forestry (林学上の森林分類)

artificial forest or man-made forest (人工林)
natural forest (天然林)

primeval forest (原生林, 原始林)

naturally-regenerated forest (天然生林)

Jomon forest (縄文の森)

The temperetures were hiher in the middle Jomon Era (ca 6300 years ago) than in the present. The southern part of Hokkaido, including Kita-Kogane region (Date City) was covered with the lush vevgetaion of deciduous broad-leaved trees.
Quercus mongolica var. grosseserrata, Quercus dentata, Aesculus turbinata, Betula platyphylla var. japonicaBetula maximowiczianaFraxinus mandshurica, Ulmus davidiana var. japonica, Ulmus laciniata, Magnolia kobus var. borealis, Magnolia obovata, Sorbus commixta, Sorbus alnifolia, Cercidiphyllum japonicum, Tilia japonica, Callicarpa japonica, Euonymus oxyphyllus, Euonymus sieboldianus, Sambucus racemosa ssp. kamtschatica, Acer amoenum, Acer mono var. mono, Elaeagnus umbellata, Prunus sargentii, Morus bombycis, Kalopanax pictus, Aralia elata, Juglans mandshurica var. sieboldiana, Viburnum opulus var. calvescens, Hydrangea serrata var. yesoensis, Actinidia arguta f. platyphylla, Actinidia polygama, Vitis coignetiae, Zanthoxylum piperitum, etc.
Taraxacum venustum, Erythronium japonicum, Paeonia japonica, Lilium cordatum var. glehnii, Trillium apetalon, Corydalis incisa, Corydalis ambigua, Anemone pseudoaltaica, Chloranthus japonicus, Polygonatum odoratum var. maximowiczii, Arisaema serratum, Lysichiton camtschatcensis, Symplocarpus renifolius, Caltha palustris var. barthei, Lythrum salicaria, etc.
Early Jomon (≈ BP9000)
Early Jomon Era

Wahington State [ plant species | wetland vegetation ]

Forest zones of the Cascades

Species are listed below first according to their general community (群集) affiliation and, within broad communities, by gross life-form (生活型). Ecological information is listed for these and other species on separate handouts. After each zone major associations found are listed, giving dominant species and general habitat conditions.
Species marked by an asterisk are typical of the zone, usually dominant. x indicates general habitat conditions where the species is most likely to be found.

Forest zones

west of the Cascades
These forests have no true counterpart in any other part of the world. Strong dominance by conifer species, longevity and productivity of dominants, highest biomass of any vegetation type.
Climate is mild and precipitation is both high and concentrated in the winter. Catastrophic climatic events (fire, hurricanes) are infrequent, so that forests may attain their maximum genetic potential.

Picea sitchensis
Tsuga heterophylla
Abies amabilis
Tsuga mertensiana

East of the Cascades
Pinus ponderosa
Pseudotsuga menziesii
Abies grandis
Abies lasiocarpa
Lodgepole Pine Zone
Many very different situations lead to the hostile environments for plant growth which characterize the Lodgepole Pine Zone. This zone is not at all widespread, but it offers special problems. It is found in sites which are either very frosty year-around, very droughty and nutrient poor (such as the Kalama Mudflow and various recent lava flows) or very moist and cold (such as high elevation bogs).

Forest zones west of the Cascades

Sitka spruce (Picea sitchensis) forest zone

Distribution: narrow band of coastal forest, stretching from south-east Alaska to Northern California. Best developed in the major river valleys of the western Olympic Peninsula.
Elevation range: usually below 150 m, but up to 600 m where mountains are close to the coast.
Climate: fog common, abundant rain, over 300 cm/yr, less than 10% as snow; temperatures mild, frosts rare, summers cool, and range narrow.
Soil: deep, rich organic soils developed primarily on flood plains, and young terraces; pH typically from 5.0 to 5.5.
Table. Sitka spruce (Picea sitchensis) forest zone
Life   Species               Wet Moist Dry Seral Comments

Trees  Picea sitchensis*           x             Climax
       Tsuga heterophylla*         x             Climax
       Thuja plicata           x
       Pseudotsuga menziesii             x   x
       Pinus contorta                    x   x
       Alnus rubra             x             x   Riparian
       Acer macrophyllum       x                 Riparian
Shrubs Acer circinatum         x   x         x
       Oplopanax horridum*     x
       Gaultheria shallon*               x   x
       Vaccinium ovatum*                 x
       V. parviolium*                        x
       Sambucus racemosa                     x
       Rubus spectabilis*      x             x
Herbs  Polystichum munitum*        x     x
       Oxalis oregana*             x
       Blechnum spicant*       x   x
       Maianthemum dilatatum       x
       Montia sibirica             x         x   Disturbance
       Tiarella trifoliata         x
       Viola sempervirens          x
       V. glabella                 x
       Athyrium filix-femina*  x   x
       Cornus unalaschkensis   x	x
       Lysichitum americanum   x
       Carex obnupta           x

Typical associations:
Picea sitchensis/Polystichum minitum/Oxalis oregana; Coastal: Tsuga heterophylla-P. sitchensis/Galtheria shallon-Vaccinium ovatum; Pinus contorta/G. shallon; Wetter sites: P. sitchensis-T. heterophylla/Oplopanax horridum-Athyrium filix-femina; Tsuja plicata/O. horridum/A. filix-femina; Seral: Acer circinatum/P. munitum; G. shallon/Vaccinium parvifolium.
Dominant species: Picea sitchensis, Tsuga heterophylla, Thuja plicata, Pseudotsuga menziesii, Abies amabilis. Pinus contorta occurs along the coast and Alnus rubra occurs on disturbed sites and river flats. Acer macrophyllum is scattered along river valleys.
Major subordinate species: Polystichum minitum, Oxalis oregana, Maianthemum dilatatum, Montia sibirica, Tiarella trifoliata, Viola sempervirens, V. glabella, Vaccinium parvifolium, and Menziesia ferruginea.
Dry site subordinates: Gaultheria shallon, Rhododendron macrophyllum, and Vaccinium ovatum.
Wet site subordinates: Oplopanax horridum, Athyrium filix-femina, Blechnum spicant, Dryopteris austriaca, and Sambucus racemosa.
Succession: Dense shrub communities often dominate post-fire or logging succession. These include combinations of Rubus spectabilis, Sambucus racemosa, and Vaccinium species. Alnus rubra is most common tree dominant in seral stands.
Special types:
  • Olympic Rainforest - much Acer macrophyllum and A. circinatum, conspicuous epiphytes, many nurse long, and Roosevelt elk strongly affecting understory structure.
  • Forest swamps - high water table, dominated by Thuja plicata and Alnus rubra, with other conifers, including Pinus monticola, present. Many species, but Lysichitum americanum and Carex obnupta are characteristic dominants.
  • Prairies - dominated by Pteridium aquilinum, with many native and introduced species.

Western Hemlock (Tsuga heterophylla) forest zone

This zone is moist and warm. It is ideal for the growth of trees. Dense stands of Douglas-fir invade following catastrophic wildfires. These stands include lesser amounts of red alder, western recedar, bigleaf maple and western hemlock. Without further disturbance the Douglas-fir is replaced by western hemlock after many centuries. This zone resonds most favorably to most management activities. It provides considerable quantities of timber and is of vital importance for many wildlife species and for high quality watersheds.

Distribution: This is widely distributed in lowland western Washington, below about 900 m, including Puget Sound and lower Cascades, Mt. Rainier, etc., grading into other zones at higher elevation.
Elevation range: near sea level to over 1000 m in western Washington; higher in drier areas, lower in wetter areas; snow depth accumulation may control upper distributional limit.
Climate: wet, mild, maritime climate with about 200 cm a typical amount; 10% falls during summer. Frosts common, with heavy snow at the higher elevations.
Soil: profiles deep, moderately acid, organic matter moderate to high, with deep litter common due to relatively slow decomposition; a variety of soil types including haplohumults (reddish brown laterites), dystrochrepts (brown podsols), and haplumbrepts (brown forest).

Western Hemlock (Tsuga heterophylla) forest zone
Life formSpeciesWetMoistDrySeralComments
TreesTsuga heterophylla*xclimax
Thuja plicata*xx
Pseudotsuga menziesii*xx
Abies grandis*x
Pinus monticolaxxbogs
Alnus rubra*xx
Acer macrophyllumx
Populus trichocarpaxx
Arbutus menziesii*x
Quercus garryana*x
ShrubsOplopanax horridum*x
Gaultheria shallon*xx
Holodiscus discolor*xxopenings
Rubus spectabilis*xx
Vaccinium ovatum*x
V. parvifolium*xx
Linnaea borealisxx
Oemleria cerasiformisx
Rhamnus purshianax
Rhododendron macrophyllumxx
Vaccinium alaskensex
Taxus brevifoliax
HerbsAchyls triphylla*x
Athyrium filix-femina*xx
Blechnum spicantxx
Clintonia uniflorax
Epilobium angustifoliumxfire
Lysichitum americanum*x
Polystichum munitum*x
Pteridium aquilinumxxovergrazed
Trifolium ovatumx
Xerophyllum tenaxxx

(plus those of Sitka Spruce Zone)

Typical associations
Wet: Tsuga heterophylla(TSHE) / Lysichitum americanum; TSHE / Athyrium filix-femina; TSHE / Oplopanax horridum / Polystichum munitum.
Mesic: Lower elevation: TSHE/Polystichum munitum; TSHE/Berberis nervosa-Gautheria; TSHE/Achyls triphylla. Drier: TSHE/Gaultheria shallon; TSHE/Cornus unalaschkensis-Achyls triphylla. Xeric: TSHE - Pseudotsuga menziesii/Holodiscus discolor; (TSHE)-Pseudotsuga menziesii - Arbutus menziesii; Abies grandis/Achyls triphylla; Quercus garryana (several associations). Higher elevations: TSHE/Vaccinium alaskense-Cornus; TSHE/ Vaccinium alaskense-Gaultheria.
Major subordinate species: Holodiscus discolor, Vaccinium parvifolium, Berberis nervosa, Gaultheria shallon, Polystichum munitum, Xerophyllum tenax, Athyrium filix-femina and many others.
Dry site subordinates: Berberis nervosa, Gaultheria shallon, Linnaea borealis.
Wet site subordinates: Oplopanax horridum, Athyrium filix-femina, Blechnum spicant, Viola glabella, Achlys triphylla, Lysichitum americanum.

Typical associations along a gradient from wet to dry: Thuja plicata/Tsuga hetterophylla/Oplopanax horridum/Athyrium filix-femina Thuja plicata/Acer circinatum/mixed herbs Tsuga heterophylla/Polystichum munitum/mixed herbs Pseudotsuga menziesii/Gaultheria shallon Pseudotsuga menziesii/Rhododendron macrophyllum

Succession: Invaders of clear cuts: Epilobium angustifolium, Cirsium vulgare, and Pteridium aquilinum; followed by shrub stage with Rubus ursinus, Acer circinatum, and Gaultheria shallon typical. Alnus rubra is most common natural invader, slowly replaced by conifer species, primarily Pseudotsuga menziesii.
Sepcial types: Edaphic prairies (e.g., Mima Mounds, Ebey's Prairie) in which forest never developed due to poor soil conditions and fire. Soils are glacial drifts with coarse texture, poor nutrient status, and well drained. Talus communities occur on steep slopes with unstable substrates. Acer circinatum usually dominates with many shrub species and the more xerophytic herbs and fern species.

Pacific Silver Fir (Abies amabilis) forest zone

Persistent winter snow packs help delimit this zone. It spans the gradient between the warm, moist Western Hemlock Zone and the very cold, moist Mountain Hemlock Zone. The forests are dominated by Douglas-fir and noble fir following large fires, but these species are eventually replaced by Pacific silver fir. This zone provides high values of many resources, but the prevailing cold climates dictate the type of management activities.

Distribution: Mid-montane slopes of Olympics and Cascades from Central BC to Oregon; requires moderate to heavy snow and mild summer temperatures.
Elevation: Usually between 600 and 1400 m; strongly influenced by topography, aspect, and snowpack.
Climate: Compared to Tsuga heterophylla zone, a much greater fraction of precipitation occurs as snow, up to 40%. At Snoqualmie Pass, annual precip. is 2600 mm, with less than 10% falling June to August. Winter snow packs are moderate, from one to three m, and temperatures are cool, with maximum summer temperature only 21°C.
Soil: Typically cryothods (podzols) with fairly thick litter accumulations; leached; acid.

Pacific Silver Fir (Abies amabilis) forest zone
Life formSpeciesWetMoistDrySeralComments
TreesAbies amabilis*xx
Tsuga heterophyllaxlower slopes
Abies proceraxxxseral
Pseudotsuga menziesiixxxfire
Pinus monticolax
Tsuga mertensianaxxhigher slopes
Chamaecyparis nootkatensisxxhigher
ShrubsVaccinium alaskense*xx
V. membranaceusx
Menziesia ferrugineax
Rhododendron albiflorumx
Gaultheria shallon*xx
Linnaea borealis*xxx
Oplopanax horridum*x
HerbsBlechnum spicantxx
Clintonia uniflorax
Cornus unalaschkensisxx
Maianthemum dilatatumx
Pyrola spp.x
Rubus lasiococcus x
Streptopus spp. x
Xerophyllum tenax xx

Typical association along a gradient from wet to dry:

Wet, low: Abies amabilis(ABAM) / Oplopanax horridum;
Wet, higher: ABAM / Rhododendron albiflorum;
Mesic, lower: ABAM / V. alaskense; ABAM / Gaultheria shallon; ABAM / Berberis nerbosa;
Mesic, higher: ABAM/Tiarella unifoliata; ABAM/Achyls triphylla-Clintonia uniflora; ABAM / V. alaskense/Clintonia uniflora;
Higher, dry: ABAM / Vaccinium membranaceum / Xerophyllum tenax

Major subordinate species: many ericades including Vaccinium spp., Menziesia ferruginea, Gaultheria spp., Chimaphila spp., Rhododendron albiflorum, and Pyrola spp. Xerophyllum tenax, Rubus lasiococcus, Cornus canadensis, and Clintonia uniflora common.
Succession: disturbed sites invaded by Pseudotsuga or A. procera, which will not regenerate under canopy conditions. Abies amabilis is usually late to invade, coming in under a mixed conifer canopy.
Special types: Alnus sinuata avalanche track vegetation; mesic meadows dominated by Pteridium aquilinum, resulting from moisture seeps or due to shallow or unstable soil.

Key to Pacific silver fir associations

The following key was designed as an aid in identifying the upper elevation associations of the Gifford Pinchot National Forest and vicinity. Environmental and management information applicable to a given site is accessed by identifying the association using the key, then referring to the detailed association description. The step in using the key are:

  1. Select a vegetationally uniform area about 25 feet (8 meters) in radius or 0.05 acre (0.02 ha) in size. The plot should be representative of a larger area of reasonably homogeneous vegetation.
  2. First identify and list tree, shrub and herb species, then estimate the cover of each. Cover is estimated to the nearest percent, up to 10 percent cover and to the nearest 5 percent thereafter. Walk around the plot area.
  3. Work step by step through the association key to a preliminary identification.
  4. Review the association description to verify the identification.
  5. Only after verification, note the management considerations for the association.

It is important to follow these steps rigorously since misidentification may lead to the wrong management considerations.The key is designed to be used in sequence. Always start at the beginning of the key and work systematically through.
The associations described in this guide are based on plot data collected throughout the forest and represent conceptual abstractions.In practice, few stands will conform exactly to the typical association description. Because vegetation varies continuously over the landscape, ecotones of transitional composition, which do not fit neatly into any described association, will be encountered. Such ecotones should be managed according to the characteristics of the associations between which they fall. In most cases, adjacent associations have similar management properties.There are about 50 common herb and shrub species used in the key and association descriptions.

Key to the plant associations and ecoclass codes for the upper elevation series, Gifford Pinchot National Forest.


  1. Tree cover in stand projected to stable state* contains less than 10% ABAM and less than 10% TSME
    _______________________________________________________________ not included in key
  2. Tree cover in stand projected to stable state contains at least 10% ABAM and/or 10% TSME ______ 3
  1. Tree cover in stand projected to stable state contains at least 10% TSME
    ____________________________________________________ Mountain Hemlock Series 5
  1. RHAL cover ≥ 5% ___________________ TSME/RHAL association CM S2-23. If not, go to 6
  2. MEFE cover ≥ 5% ___________________ TSME/MEFE association CM S2-21. If not, go to 7
  3. VAME cover ≥ 5%
    _________ TSME/VAME association CM S2-10. If not, it is undescribed TSME association
  1. Tree cover in stand projected to stable state contains less than 10% TSME
    ______________________________________________________ Pacific Silver Fir Series 8
  1. OPHO cover ≥ 5% __________________ ABAM/OPHO association CF S3-51. If not, go to 9
  2. RHAL cover ≥ 5% __________________ ABAM/RHAL association CF S5-50. If not, go to 10
  3. MEFE cover ≥ 5% __________________ ABAM/MEFE association CF S2-54. If not, go to 11
  4. TIUN cover ≥ 5%; or TIUN cover at least 1% along with at least two wet site herbs
    _____________________________________________ ABAM/TIUN association CF F1-52
  5. TIUN cover ≤ 5% and less than two wet site herbs present _______________________ 13
  1. VAAL plus VAOV cover ≥ 5% ____________________________ go to 14. If not, go to 15
  1. GASH cover ≥ 2% __________________ ABAM/VAAL-GASH association CF S2-55.

If not, it is ABAM/VAAL association CF S2-57

  1. GASH cover ≥ 2% ______________________________ ABAM/GASH association CF S1-52
  2. GASH cover ≤ 2% _______________________________________________________ 17
  1. BENE cover ≥ 5% ___________________________ ABAM/BENE association CF S1-51
  2. BENE cover ≤ 5% ____________________________________________________ 19
  1. VAME cover ≥ 5% _________________________________________________ 21
  1. Several plots other than XETE present, usually including CLUN and ACTR
    _____________________________ ABAM/VAME/CLUN association CF S2-56
  2. XETE most prominent herb; other herbs inconspicuous
    _____________________________ ABAM/VAME/XETE association CF S2-51
  1. VAME cover ≤ 5%, cover of herb layer at least 10%
    _________________________________ ABAM/ACTR-CLUN association CF F2-53

* stand condition at age 300 or more

Topik C, Halverson NM, Brockway DG. 1986. Plant association and management guide for the western hemlock zone. P Pacific Northwest Region, USDA Forest Service

Mountain Hemlock (Tsuga mertensiana) forest zone

The harsh, high elevations include this zone. Most of the year snow-packs prevail and frost can occur at any time of the year. The forest canopy provides a generally a continuous cover. Biological processes are slow and result in fragile ecosystems. The proximity to spectacular alpine areas and the relatively open understory characteristics of the forests make this zone a favorite for many recreations.
Distribution: Forms timberline and forest/meadow complex in moist to wet mountains of Olympics and Cascades; primarily west of Cascade Crest.
Climate: Cold, wet, with heavy snow pack. At Paradise, over half the annual precip. of 2700 mm occurs as snow, with less than 10% falling during summer.
Elevation: This is the highest forest zone in western Washington, ranging form about 1300 to 1900 m, depending on latitude and local factors (topography and aspect).
Soil: poorly developed podzols and gleys (hydric soils).
Typical associations:
On typical sites: Tsuga mertensiana (TSME)-Abies amabilis/Vaccinium membranaceum;
higher elevations: Chamaecyparis nootkatensis-TSME/Rhododendron albiflorum-Vaccinium spp.; TSME/ Rhododendron albiflorum;
moist, lower elevations: A. amabilis-TSME/V. alaskense;
mesic, lower elevations: TSME/V. alaskense.
Table. Mountain Hemlock (Tsuga mertensiana) forest zone (Klinka weighted average method)
Lifeform Species             Wet Moist Dry Seral Comments

  Tsuga mertensiana          x   x
  Abies amabilis*            x   x               lower slopes
  Abies lasiocarpa*                    x   x
  Pinus contorta                       x   x
  Chamaecyparis nootkatensis x  x                higher slopes
  Vaccinium membranaceus*       x      x   x     fire tolerant
  Vaccinium alaskense           x
  Rhododendron albiflorum*   x  x
  Phyllodoce empetriformis      x          x
  Erythronium montanum       x
  Pyrola secunda                x
  Rubus lasiococcus             x
  Valeriana sitchensis       x
  Veratrum viride            x  x
  Xerophyllum tenax*            x      x

Forest zones west of the Cascades

Ponderosa Pine (Pinus ponderosa) forest zone

Distribution: common at the lower timberline along the eastern base of the Cascades, and in the Okanogan highlands and higher elevations surrounding the Columbia basin. Elevations range from about 500 m to 900 m.
Climate: low precipitation, only 50 to 60 cm/yr, with little snow and pronounced summer droughts. Temperature range is great.
Soil: moderately acid with low organic content but thick litter due to slow decomposition rates.
Table. Ponderosa Pine (Pinus ponderosa) forest zone
Lifeform  Species               Wet Moist Dry Seral Comments

Trees     Pinus ponderosa*          x     x    x
          Pseudotsuga menziesii*    x
          Pinus contorta                       x    fire
          Abies grandis             x
          Larix occidentalis              x    x    fire
Shrubs(a) Amelanchier alnifolia     x
            nevadensis*                   x
          Ceanothus velutinus             x    x    fire
          Prunus emarginata*        x     x
          Purshia tridentata              x
          Symphoricarpos albus*           x
Herbs     Achillea millefolium*           x
          Agropyron spicatum*             x
          Arenaria macrophylla            x
          Balsamorhiza saggitata          x
          Carex geyeri*                   x
          Festuca idahoensis*             x
          Phlox diffusa                   x
          Pteridium aquilinum*      x     x

(a) see also Douglas Fir Zone, below

Typical associations: Pinus ponderosa (PIPO)/Purshia tridentata; PIPO/Symphoricarpos albus; PIPO/Festuca idahoensis; PIPO/Calamograostis rubescens-Carex geyeri; PIPO-Pseudotsuga menziesii (PSME)/Agropyron spicatum-Carex geyeri.
Subordinate species: highly variable due to locate. Symphoricarpos albus, Festuca idahoensis, Agrophyron spicatum and Purshia tridentata are dominate in large areas.
Succession: fire is a major component of the ecosystem. P. ponderosa is fire resistant and repeated, mild fires scar, but no not destroy adults. Fires kill invading small trees of other conifers and prevent succession. Fire also enhances grasses at the expense of shrubs. Ceanothus velutinus (a symbiotic nitrogen-fixing species) invades after hot fires.
Special type: Areas of special soil (e.g., serpentine) may support stable populations of Pinus contorta and a limited array of drought tolerant herbs and shrubs.

Douglas fir (Pseudotsuga menziesii) forest zone

This zone is widely distributed throughout the western US. In contrast to west-side forests, here Pseudotsuga is truly a climax species.
Distribution: widely distributed in western US, found above Ponderosa Pine forest; here Douglas fir is true climax species. Overlapping with other forest types in response to topography and disturbance.
Elevation: Typical range in central Washington is from 600 to 1300 m, overlapping with P. ponderosa in mesic sites at the low end and with Abies grandis on xeric sits at the high end.
Climate: slightly cooler and more moist than Ponderosa Pine zone, with precipitation about 100 cm/yr, scant summer rain, and greater snow pack.
Soil: slightly podzolic, more leached than soils of Ponderosa Pine zone, tending more towards Haplorthods (gray wooded soils, with podzolic tendencies)
Table. Douglas fir (Pseudotsuga menziesii) forest zone
Life form Species              Wet Moist Dry Seral Comments

Trees  Pseudotsuga menziesii*   x   x    x
       Pinus ponderosa*             x
       Pinus contorta                    x
       Larix occidentalis           x    x
       Abies grandis            x
Shrubs Amelanchier alnifolia    x   x
       Berberis nervosa         x
       Holodiscus discolor*     x   x
       Pachistima myrsinites*   x
       Prunus emarginata        x
       Rosa woodsii             x   x
       Spirea betulifolia*      x
       Symphoricarpos albus         x
Herbs  Achyls triphlla          x
       Coralorhiza sp.          x   x
       Cornus unalaschkensis    x   x
       Lupinus polyphyllus      x                  Openings
       Pyrola secunda           x

Typical associations: Pseudotsuga menziesii (PSME)/Symphoricarpus albus; PSME/Holodiscus discolor; PSME/Arctostaphylos uva-ursi; PSME/Pachistima myrsinites; PSME/Vaccinium spp./Rubus lasiococcus; PSME/Berberis nervosa-Gaultheria shallon; PSME-Abies grandis/Acer circinatum/Trientalis latifolia; PSME-Abies lasiocarpa/ Vaccinium membranaceum.
Subordinate species: similar to those of drier Tsuga heterophylla zone, plus Agrophyron spicatum, Carex geyeri, Arctostaphylos nevadensis, Arnica spp. and many others.
Succession: fire controls major distribution; P. menziesii will dominate in stable stands, but any of the trees listed above may dominate if fires have been recent.

Grand fir (Abies grandis) forest zone

This zone reflects dry, continental climates with extremes in temperature and moisture. It is highly productive and offers many opportunities for wildlife, recreation and timber utilization.The relatively dry climates dictate different management strategies than in the Western Cascade areas under the maritime climatic influence.
Distribution: restricted in Washington, found in the eastern Cascades sandwiched between Douglas fir forests in direr, lower sites and subalpine fir or western hemlock forests in moister, higher sites.
Elevation: Abies grandis is dominant from 1000 to 1200 m in mesic habitats, the central Cascades.
Climate: Moderate in moisture and temperature; limited summer drought. Summer drought ameliorated by protected aspects and occurrence in riparian setting.
Soil: Poorly developed, but deep in most places due to volcanic ash accumulations. They are podzolic, primarily in the Haplorthods and Haplubrets groups. They are slightly acidic and have moderate organic matter.
Typical associations: Abies grandis (ABGR)-Tsuga plicata/Acer glabrum/Clintonia uniflora; ABGR/Pachistima myrsinites; ABGR/Vaccinium membranaceum; ABGR/Pyrola sp.
Subordinate: Pachistima myrsinites, Vaccinium membranaceum, Rosa gymnocarpa, and Ribes lacustre. are common shrubs, while mesophytic herbs such as Arnica cordifolia, Galium triflorum, Arenaria macrophylla, Linnaea borealis, Aenocaulon bicolor, and Trillium ovatum are common.
Succession: Ceanothus velutinus is a major brushfield dominant after fire. Many seral tree species actually grow better in this zone than where they are climax, but A. grandis can shade them out.
Table. Grand fir (Abies grandis) forest zone
Life form/Species        Wet Moist Dry Seral Comments

  Abies grandis*              x
  Pseudotsuga menziesii*      x     x
  Pinus ponderosa                   x   x
  Picea engellmannii          x               Forest pockets
  Abies lasiocarpa                  x   x     Forest pockets
  Tsuga mertensiana       x                   High elevation
  Acer glabrum*           x
  Pachistima myrsinites*      x
  Vaccinium membranaceum*     x     x
  Rosa spp.                   x
  Adenocaulon bicolor               x   x     Trail sides
  Arenaria macrophylla        x     x
  Arnica cordifolia       x   x
  Clintonia uniflora      x   x
  Linnaea borealis*           x
  Pyrola spp.             x   x               Dark habitats

Subalpine fir (Abies lasiocarpa) forest zone

Distribution: Near timberline in direr timberline sites; NE Olympics, the Okanogans, drier eastern Cascades (including Mt. Rainier) and Wenatchee Mountains.
Elevation: The lower limit is usually below 1400 (1500) m, extending to local treeline (2000 m als). It abuts Abies grandis zone forest in mesic sites, Pseudotsuga zone forests on xeric sites, and many contact Tsuga heterophylla zone in some places.
Climate: (Climatic data are scarce) Cool and moist with moderate snow packs (locally heavy), but some drought; growing season relatively short with summer maxima under 15°C.
Soils: Generally cryothods (podozols with thin humus layers). Very acid due to low temperatures and slow decomposition of humus.
Typical associations: Abies lasiocarpa (ABLA)/Pachistima myrsinites/Clintonia uniflora; ABLA/Menziesia ferruginea; ABLA/Phyllodoce empetriformis; ABLA/Vaccinium scoparium-Juniperus communis; Pinus albicaulis (PIAL)-ABLA/Arctostaphylos-Pachistima; ABLA-Picea engelmannii/Vaccinium membranaceum; ABLA-Larix lyallii/Phyllodoce-Vaccinium.
Subordinate species: Pachistima myrsinities, Clintonia uniflora, Viola glabella, Adenocaulon bicolor, Arenaria macrophylla, and many other mesophytes. Ericads dominate in the wetter portions, graminoids in more open, upper areas.
Succession: Pinus contorta is the major seral tree, though Picea is usually seral as well. Closed forests in this zone will generate into monospecific crown dominate by A. lasiocarpa; upper, open forests will be more complex.
Special type: A weakly developed A. lasiocarpa zone forest can be recognized in the North Eastern Olympics at timberline between Hurricane Ridge and the Blue Mountain areas.

Typical associations: Abies lasiocarpa (ABLA)/Pachistima myrsinites/Clintonia uniflora; ABLA/Menziesia ferruginea; ABLA/Phyllodoce empetriformis; ABLA/Vaccinium scoparium-Juniperus communis; Pinus albicaulis (PIAL)-ABLA/Arctostaphylos-Pachistima; ABLA-Picea engelmannii/Vaccinium membranaceum; ABLA-Larix lyallii/Phyllodoce-Vaccinium.
Subordinate species: Pachistima myrsinities, Clintonia uniflora, Viola glabella, Adenocaulon bicolor, Arenaria macrophylla, and many other mesophytes. Ericads dominate in the wetter portions, graminoids in more open, upper areas.
Succession: Pinus contorta is the major seral tree, though Picea is usually seral as well. Closed forests in this zone will generate into monospecific crown dominate by A. lasiocarpa; upper, open forests will be more complex.
Special type: A weakly developed A. lasiocarpa zone forest can be recognized in the North Eastern Olympics at timberline between Hurricane Ridge and the Blue Mountain areas.

Table. Subalpine fir (Abies lasiocarpa) forest zone
Life form/Species         Wet Moist Dry Seral Comments

  Abies lasiocarpa*            x     x   x
  Picea engellmannii       x   x
  Pinus contorta                     x   x     Fires
  Larix lyallii            x   x               Highest slopes
  Pinus albicaulis                   x         Higher slopes
  Juniperus communis                 x
  Pachistima myrsinites*       x     x
  Vaccinium spp.               x
  Phyllodoce empetriformis x
  Clintonia uniflora           x
  Luetkea pectinata            x     x   x
  Viola spp.               x   x

Taking notes on July 30 2014


... and the Forest Ends

Just as there is a northern tree limit on the earth, there is also an upper tree limit on mountains -- sometimes called "timberline." Whether it's latitude or altitude, tree limit is determined by the same factors: length of the growing season, combined with temperature and wind.

↑ You are here (northern edge of Brooks Range, Alaska): 777 m - elevation of timberline
↑ Alberta, Canada: 2286 m
↑ Colorado, US: 3658 m
↑ Close to the equator: 5791 m
Timberline gets higher as you get closer to the equator.

Limits for differnt trees along the Dalton Highway

white spruce limit - you are here
black spruce limit - 1 mile south
paper birch limit - 25 miles south
quaking aspen limit - 55 miles south