Introduction When plants grow, they take up nutrients they need from the soil. These are inorganic salts, often simply referred to as minerals. The most important of these mineral nutrients to plants are nitrogen, potassium, phosphorus and calcium. Certain other elements in the soil may be poisonous in soluble form, while others may be important to growth but are only present in very small quantities. In most ecosystems, there is a bank of these nutrients laid down deep in the soil which plants can draw on.
More nutrients enter the ecosystem as rainwater.
The nutrients are then re-used by the plants, and as they are recycled in this way there is a constant supply of them. The rainforest is different from most temperate ecosystems because though it is highly productive, it generally grows on soils which do not have many nutrients. While the rainforest ecosystem does have very efficient ways of re-using nutrients and preventing their loss, some research indicates that certain rainforests in fact grow on fairly fertile soils. So a word of caution - neither rainforests nor the soils they grow on are all the same, and the systems of recycling are complex. There is no complete or easy explanation of how the cycles operate.