How does the vegetation change as you climb from the base to the top of the mountain, and why is this happening?

At the foot of the mountains, the climate is dry, corresponding to the steppe and even desert. Rising higher, humidity increases and therefore the most favorable conditions for vegetation development. Mixed, coniferous and deciduous forests grow here. Above, forests are replaced by light forests, but the climate is favorable for the growth of grasses. Above, it is even colder, open woodlands are replaced by shrubs, grasses with mosses and lichens. Above it is cold, as in the arctic steppes, only moss grows. On the tops of the mountains, nothing grows. Glaciers.