Six major ecosystems, or biomes, are located around Earth. The desert has soil that is rich in minerals. Prairie dogs and snakes live in American grasslands. The cold biome in the far north is the tundra. Here, a layer of permanently frozen soil called permafrost keeps water from flowing downward. The greatest diversity of plants can be found in tropical rain forests. Mostly conifers grow in the taiga. Deciduous forests have many different trees that lose their leaves each autumn.