What does the 'O' horizon in soil composition represent?

The 'O' horizon in soil composition represents organic matter, which is a crucial component of soil health and fertility. This layer is typically found at the very surface of the soil and is primarily composed of decomposed leaf litter, plant material, and other organic matter. The presence of the 'O' horizon is significant because it plays a key role in providing essential nutrients to plants and enhancing the soil's ability to retain moisture.

This horizon is vital for soil ecology, as it supports a variety of organisms that contribute to nutrient cycling and soil structure. The organic matter in this layer also improves the soil's capacity to hold moisture and air, which benefits root growth and overall plant health. In contrast, the other layers, such as the subsoil and parent material, do not have the same concentration of organic matter or nutrient availability, making the 'O' horizon distinct in its importance to agricultural and ecological systems.