What substance do decomposers primarily recycle back into the soil?

Decomposers, such as bacteria and fungi, play a critical role in nutrient cycling within ecosystems. Their primary function is to break down organic matter from dead plants, animals, and waste products, releasing essential nutrients back into the soil. Among the various nutrients, nitrogen and phosphorus are particularly important because they are vital for plant growth and are often limiting factors in ecosystems.

When decomposers break down proteins, nucleic acids, and other organic compounds, they convert nitrogen in these substances into forms that plants can readily absorb—like ammonium and nitrates. Similarly, phosphorus is released from organic matter, becoming available for uptake by plants. This recycling process is crucial for maintaining soil fertility and supporting the growth of new plant life, which in turn supports herbivores and higher trophic levels in the food web.

In contrast, while carbohydrates are components of organic matter and can be broken down, they are not the primary nutrients that are recycled. Water is also essential for life and is involved in many ecosystem processes, but it is not a substance that decomposers specifically recycle like nutrients. Glucose is a product of photosynthesis and serves as an energy source, but it is not what decomposers primarily return to the soil in nutrient cycling.