The major types of vegetation in the world are grouped as forests, grasslands, scrubs and tundra. In areas of heavy rain, huge trees can be found. Forests are abundant in areas of heavy rainfall. With moisture and rainfall the density of forests declines. In moderate rainfall areas, grasslands are found. In this areas, we find thorny shrubs and scrubs. Plants here have deep roots and leaves have thorny surface to reduce loss of moisture. The tundra vegetation consists of mosses and lichens.