Carbon and Nutrients

2.3 Biological Characteristics

Almost all of life’s energy ultimately comes from the sun through photosynthesis that occurs in plant leaves. That means that aboveground and belowground processes are inherently connected. The soil food web is critical for sustaining biological activity, diversity, and productivity. The interactions among plants, microbes, and animals are key to functions such as regulating the flow of water and storing and cycling nutrients and other soil components. In this unit, we discuss the life forms that make up soil ecosystems and their beneficial, predatory, and competitive interactions—holding in mind that there is great variation in soil biological characteristics in space and over time.

Learning Outcomes

After completing this section you will be able to:

• Describe how plants cycle carbon, including feeding the soil food web

• Describe the key roles that microbes play in facilitating soil processes

• Describe some roles invertebrates and vertebrates play in the soil food web and in other soil functions

Arrows point in the directions that energy and nutrients are moving. For example, livestock eat plants; manure becomes organic matter.