The types of plants in this ecozone and the lushness of their growth are strongly influenced by their position on mountain slopes, which determines the amount of available soil moisture and sunlight. Western slopes often have more luxuriant plant cover than eastern ones, since clouds deposit most of their moisture on western slopes before continuing east. Similarly, northern and southern mountain slopes show pronounced differences in plant growth because of differences in the amount of sunlight they receive. South-facing slopes tend to be warmer and drier, conditions that favour soil nutrient release and plant growth common in more temperate climates. Plants on north-facing slopes typically include species better adapted to cold climates.
Four main vegetation zones are found in this ecozone. Extensive areas of alpine tundra occur on the upland plateaus and highest mountain slopes. Here, scattered among lichens, sedges, and mosses are species that typically possess very large flowers relative to the rest of the plant. Their function is to attract insect pollinators during the short growing season.
Further downslope is the subalpine transition zone, which is dominated by scattered Alpine Fir trees and a dense understory of Willow and Shrub Birch. White and Black Spruce replace firs in the lower parts of this zone. Below the subalpine zone on the lower flanks of the mountains is the montane zone, characterized by spruce-lichen woodlands and flat benches of Lodgepole Pine. Isolated stands of deciduous trees such as Trembling Aspen and Paper Birch are found here, growing in the aftermath of forest fires.
In the lowland zone, sheltered conditions, abundant moisture and relatively well-developed soils promote the growth of dense spruce-feathermoss forests and riverside communities of Balsam Poplar, Willow, and Alder. Marshes and other productive wetlands are also common in this zone, particularly along flat river valleys. Wetlands reach their greatest extent in the Old Crow Flats, a vast plain of wetlands and lakes. Many of the lakes take on a natural square like form.