soil is made up of all the nutrients needed by plants to live. Some areas of the world like desert regions have very poor soil. Here, it is difficult for complex plant life to take hold. Tropical rain forests also have poor soil. Yes, the rainforest region gets enough rainfall to grow plants, but the poor soil found in rain forests is caused by so many living plants. These plants have the nutrients right inside themselves, so nutrients are not abundantly found in the soil.