Soil Most of the soil in tropical rainforests is ancient and infertile. In temperate forests the soil consists of a deep, plant-material rich layer, called humus. Plants can bury their roots deep into the ground maximising their ability to absorb available nutrients. In wet tropical regions the humus layer is much thinner because torrential downpours constantly wash minerals and organic material from the soil. Efficient decomposition of forest debris and a shallow root system allows plants to take up nutrients immediately from the forest floor.
Saprophytes are organisms that act as rainforest decomposers.
Some fungi, called mycorrhizals, also carry out this function. Decomposers can often break down dead animals and vegetation within 24 hours, with the help of warmth and wetness, which help accelerate decomposition, . Leaf litter is often not more than 1 or 2 inches thick on the forest floor of tropical rainforests. In contrast, decomposition in the colder and less humid montane forests can sometimes take up to six weeks. Many saprotrophs are so small that they cannot be seen with the naked eye.