Forests sometimes contain many tree species within a small area (as in tropical rain and temperate deciduous forests), or relatively few species over large areas (e.g., taiga and arid montane coniferous forests).
Forests sometimes contain many tree species within a small area (as in tropical rain and temperate deciduous forests), or relatively few species over large areas (e.g., taiga and arid montane coniferous forests).
作为普遍规则，受被子植物支配的森林（阔叶林）比那些受裸子植物支配的森林（松树或针叶林）物种丰富，虽然有例外存在（例如，种类匮乏的白杨和桦树生长在北纬度地区）。