altitude, temperature, humidity, soil composition, solar radiation, wind

Elevational zones

Cascades

[forest zones of the Cascades]
[plant species in Washington]

e.g., sand dune, salt marsh

Jayawijaya Mountains, Indonesia

This vegetation may be divided into two broad types: subalpine meadow complexes occur due to heavy snow pack and topographic features, often mixed with tree vegetation. Above this zone is a truly alpine vegetation in which the growing season is everywhere too short for tree growth. All such vegetation requires high elevation. How high depends upon the vegetation is lower than what would be expected on the basis of current climate. In the Olympics, the heavy snow pack acts to limit tree growth; on Mount St. Helens, the youth of the cone (and occasional set backs) precludes a climatic tree line. All the Washington volcanoes, the Olympics, and most of the Cascades have subalpine or alpine meadow vegetation.
Elevation: First subalpine meadows begin as low as 1340 m on Mount St. Helens and 1400 m on Mt. Baker and true alpine conditions usually begin above 2100 m or higher.
Climate: Short growing season with extensive snow accumulates in western Washington.

A. Subalpine Meadows

1. Phyllodoce-Cassiope-Vaccinium (Heath scrub) association: Dominance is by one or more of these ericaceous shrubs; typical associations that occur broadly in western Washington include:
   1. Phyllodoce empetriformis-Vaccinium deliciosum association. This association also usually contains Cassiope mertensiana, Leutekea pectinata, and Antennaria lanata. Usually on moist, well drained sites with limited snow accumulation and relatively long growing season. Soils are usually Cryorthods (podzols).
2. Lush Herb: These meadows are floristically rich and have dominance shared by many species in different locales.
   1. Valeriana sitchensis-Veratrum viride association has a rich group of associates including Lupinus latifolius, Castilleja parvi-flora, and Heracleum lanatum. Occurs on steep, well-watered slopes, especially where avalanches are common.
   2. Carex spectabilis association that occurs primarily in late snow melt areas, with Lupinus latifolius and Polygonum bistortoides always present.
   3. Rubus parviflorus-Epilobium angustifolium association occurs mainly in the North Cascades on steep exposed slopes with a long snow-free season. It is a low elevation type controlled more by soil conditions that by climatic conditions.
3. Carex nigricans association: These associations always occur in wet sites with a short growing season due to late snow melt. They are usually surrounded by associations requiring longer growing periods (e.g., heather associations).

4. Rawmark associations: These are associations that pioneer rocky or extremely disturbed conditions. They vary greatly from place to place. The more important include these:
   1. Saxifraga tolmiei association, common on exposed sands and gravels.
   2. Luetkea pectinata associations that often colonize talus slopes. Luetkea may be found in many conditions, including stable associations.
   3. Antennaria lanata association found on flat, shallow soil conditions drier than conditions dominated by Carex nigricans.
   4. Phlox diffusa dominates subalpine early snow melt communities in many places, growing with species such as Allium crenulatum and Lomatium martindalei
5. Festuca associations: Grassy, dry meadows dominated by Festuca viridula are common on Mt. Rainier; in the Olympics, Festuca idahoensis appears to be the functional equivalent. The fescues have broad moisture tolerances and will occur with a variety of herbs depending on location and moisture status.

B. Alpine communities

The true alpine zone is limited in Washington due to heavy snow packs. Much of it less on recent volcanoes where the substrates are young. These vegetation types are generally found above 2300 m. Snow accumulation and wind, combined with soil factors do much to control distributional patterns. Soil instability is a major feature of alpine vegetation, leading to solifluction terraces and stone stripes, among others. Major studies have been conducted in the North Cascades, Olympics, Mt. Rainier, and the Enchantment Lakes. Typical assemblages include the following from Mt. Rainier, but there are many variants.

1. Empetrum nigrum-Lupinus lepidus association, a rich, mesic community with relatively high cover.
2. Arctostaphylos uva-uris-Solidago spathulata association is a rich, warm site association with strong dominance by scrubby species, including Juniperus communis and Potentilla fruticosa.
3. Arenaria obtusiloba-Lupinus lepidus association is a very rich, xerophytic association of typically cushion plants. Phlox diffusa and Silene acaulis are common
4. Phyllodoce gladuliflora-Aster alpigenus association is low in richness, high in cover. The heather dominates cool, moist habitats in which this association occurs. Soils are stable, acid.
5. Pedicularis-Carex spectabilis association from a mesic turf association.
6. Erigeron aureus-Lupinus lepidus association is a dry, open herb community on well-drained soils.

In other areas, homologous associations and additional associations have been described. Associations vary clinally from north to south and from east to west.

Japan: needle-leaved forest (Honshu), or Betula maximowicziana forest (Hokkaido)

Pseudo-alpine zone (偽高山帯)