What explains the diversity of the diversity of the earth’s vegetation?

The globe has a huge area and, accordingly, in its different corners there are different conditions for plant life. It is this fact that explains the diversity of the Earth’s vegetation cover. For example, in tropical and subtropical forests, where there is a lot of moisture and heat, plants with wide fleshy leaves will grow, cacti grow in the desert that are able to accumulate moisture inside themselves, and in the tundra there are plants that can live in difficult conditions, they usually have low stem and dull color.