Microorganisms and fungi break down wood and return carbon to the biogeochemical cycles. If these organisms become absent, carbon would accumulate in the wood, where it could not be recycled into the environment. The fixation of nitrogen is dependent on microorganisms mostly through biological nitrogen fixation. Soil microbes (bacteria and fungi) are essential for decomposing organic matter and recycling old plant material. Some soil bacteria and fungi form relationships with plant roots that provide important nutrients like nitrogen or phosphorus.Microorganisms have several vital roles in ecosystems: decomposition, oxygen production, evolution, and symbiotic relationships. Decomposition is where dead animal or plant matter is broken down into more basic molecules. This process only happens because of the microorganisms that find their way into the dead matter.

They decompose dead plants and animals, releasing carbon dioxide. They also turn ammonia into nitrites.

Explanation:

Carbon Cycle Microbes and fungi decompose dead animals, plants and matter. When they do so, they release carbon dioxide into the air due to respiration and contribute to the carbon cycle.

Nitrogen Cycle In the soil and ocean there are certain microbes that have the ability to convert ammonia into nitrites. This contributes to the nitrogen cycle.