THE NUTRIENT CYCLE/RECYCLE IN THE RAINFOREST The majority of nutrients in the tropical rainforest are stored in biomass. Biomass is all the living things in an ecosystem, including plants and animals. Nutrients are rapidly recycled in the tropical rainforest biome. The warm, moist climate provides ideal conditions for decomposers to break down organic material in the litter layer quickly. The litter layer is all the dead organic material such as fallen leaves, dead vegetation, or dead animals on the soil’s surface. Vegetation takes up dissolved nutrients in the soil. The soil is formed by mixing dead organic material with weathered bedrock. Soils in the rainforest are mainly thin and poor. Nutrient levels in the soil are low due to the leaching (washing away of nutrients) by the heavy equatorial rain. This leaching means that the lower layers of the soils lack the nutrients and minerals the lush vegetation needs. Also, rainforest vegetation rapidly absorbs nutrients from the soil. Soils are often red in colour as they are rich in iron. The nutrient cycle in the rainforest is an excellent example of interdependence. The diagram above shows the links between different stores of nutrients in the rainforest. Decomposers rely on fallen leaves, branches and dead animals to thrive. In turn, nutrients from decomposed matter enter the soil, providing nutrients to support the growth of vegetation consumed by primary consumers. The nutrient cycle in the rainforest is very fragile. If a nutrient flow changes, this can have a negative impact on the ecosystem. NUTRIENTS CYCLE -> FOOD CHAIN -> FOOD WEB Tropical rainforests have competition for resources and sunlight. Many of the animals and plants are in competition with one another and in many cases they are also reliant upon one another. Changes in one part of the ecosystem, either the living or non-living, could be very damaging for this ecosystem. The loss of some tree cover to deforestation or fire would affect both the water and nutrient cycles for example, and cause soil erosion, increased loss of nutrients from the soils via leaching and extra flooding. Similarly, if one of the elements of the tropical forest food web were to change, there would be knock on impacts throughout that food web. Organisms within an ecosystem are classed as producers, consumers or decomposers. Energy flows through these organisms within the ecosystem. Producers, such as trees, produce food and begin this cycle: using energy from the sun, they produce food. They do this by photosynthesis. Most producers are plants, but some small organisms produce food through photosynthesis as well. Producers are eaten by primary consumers that cannot produce food themselves, such as a giraffe. Primary consumers are herbivores which means they only eat plants. Secondary consumers are carnivores such as lions. In a simple food chain, secondary consumers eat primary consumers. Decomposers and break down dead plants and animals. They also break down the waste of other organisms. Examples of decomposers include bacteria and fungi. Decomposers get their energy from breaking down dead material, e.g. dead producers, dead consumers or fallen leaves. When dead material is decomposed, nutrients are released into the soil. These nutrients are then taken up from the earth by plants. Decomposers are very important for any ecosystem. If they weren’t in the ecosystem, the plants would not get essential nutrients, and dead matter and waste would gather. A food chain shows the relationships between feeding groups, illustrating energy flow from producer to tertiary consumer. A food web shows lots of food chains and how they overlap. TROPHIC LEVEL Trophic levels refer to a level or position in a food chain or food web. First level -> They produce their own food (through solar energy = photosynthesis or decomposing litter), so they do not need to consume other plants or animals and produce (=are) food for other animals. They are typically the most abundant organisms found in the ecosystem. Second level -> the herbivorous consumers, or animals that feed on plants. Third level and above -> carnivorous consumers: animals that are considered “meat eaters” because their energy comes directly from other animal products. The carnivores are broken into tiers; the first level carnivores (third trophic level) consist animals that generally consume small herbivores. For the second level, third level, and top carnivores (fourth, fifth … level), each level consumes more energy than the last.
