What primarily influences the C:N ratio during decomposition of organic materials?

The C:N ratio during the decomposition of organic materials is primarily influenced by the microorganisms' nitrogen use. This ratio represents the carbon to nitrogen content in organic matter, and it plays a critical role in the decomposition process.

Microorganisms, such as bacteria and fungi, are responsible for breaking down organic matter. These decomposers require both carbon and nitrogen to thrive and reproduce. When organic material is rich in carbon (such as in plant residues), microorganisms will utilize the available nitrogen in the environment to balance their nutritional needs. If the C:N ratio is high, meaning that there is a greater proportion of carbon relative to nitrogen, it can slow down the decomposition process since microorganisms will need to source additional nitrogen to break down the carbon effectively.

As they metabolize the organic material, microorganisms alter the C:N ratio dynamically, reflecting their growth and nitrogen uptake. Thus, their use of nitrogen directly affects how quickly and efficiently decomposition occurs.

In contrast, while soil temperature, oxygen availability, and organic matter age do influence decomposition processes, they are not as central to the C:N ratio's specific dynamics as the microorganisms' nitrogen use. Temperature can enhance or inhibit microbial activity, oxygen is necessary for aerobic decomposition processes, and organic matter age may affect its nutrient content,