1. Decomposed Plant and Animal Matter:
* Dead roots, leaves, stems, and branches: These are the primary sources of SOM, providing carbohydrates, lignin, and other complex molecules.
* Animal remains: Including insects, worms, and small mammals, contributing proteins, fats, and chitin.
2. Microbial Biomass:
* Bacteria and fungi: These microorganisms break down the dead organic matter, releasing nutrients and transforming them into different forms.
* Microbial products: Including enzymes, exopolymers, and cell debris, which contribute to SOM's stability and function.
3. Humus:
* Stable, decomposed organic matter: This is the end product of microbial decomposition, highly resistant to further breakdown, and rich in carbon. Humus is responsible for many of SOM's beneficial properties.
4. Other Components:
* Living organisms: Including earthworms, nematodes, and other invertebrates, which play a crucial role in soil structure and nutrient cycling.
* Freshly added organic matter: This includes manure, compost, and other materials that are still undergoing decomposition.
In summary: SOM is a dynamic mixture of decomposing plant and animal material, microbial life, and stable humus. This intricate web of organic components is essential for soil fertility, water retention, and overall ecosystem health.
