The following examples justify the given statement
(i) Between the heights of 1,000 and 2,000 m, wet temperate type of forests are found. Evergreen broad-leaf trees such as oaks and chestnuts predominate.
(ii) Between 1,500 and 3,000 m, temperate forests containing coniferous trees like pine, deodar, silver fir, spruce and cedar are found.
(iii) At high altitudes, generally more than 3,600 m above the sea-level, temperate forests and grasslands give way to the alpine vegetation. Silver fir, junipers, pines and birches are the common trees of these forests.
(iv) At higher altitudes, mosses and lichens form part of tundra vegetation. Thus, it can be concluded that in mountainous vegetation due to decrease in temperature.