Climax vegetation.....

When vegetation first starts growing in newly formed soil, it is at a disadvantage because the soil will not be nutrient-rich. As the plants wither, it has gleaned more and more nutrients from dead plants- and more and more plants are able to grow successfully in the soil. Climax vegetation occurs when the vegetation is totally suited to the soil in the given climate. In reality this can never last permanently due to the ever-changing environment. Rain forests have developed in the areas where the soil is very fertile and where there is a great deal of rainfall. The varied vegetation suggests the soil is extremely nutrient-rich.