The O horizon, also known as the organic layer, is the topmost layer of soil found in forested areas. It consists primarily of organic matter, such as decomposed leaves, plant material, and other organic debris. This layer is crucial for soil health as it provides nutrients and supports a diverse ecosystem of microorganisms and insects. The O horizon plays a vital role in the soil formation process and helps retain moisture. It is typically dark in color due to the high concentration of organic material. Understanding the O horizon is essential for fields like agriculture, ecology, and environmental science.