Soil Composition and Processes

This video introduces soil systems in the context of IB Environmental Systems and Societies. It covers the concept of soils as systems with inputs, outputs, storages, and flows. The video explains the soil profile, detailing the O, A, B, C, and R horizons, and discusses the components and transfers within soils, such as biological mixing and leeching. It also covers inputs like leaf litter and outputs like soil erosion, as well as transformations like decomposition, weathering, and nutrient cycling. The video highlights the importance of soil particle size in determining soil quality and productivity, and concludes with a call to view soils as ecosystems with both abiotic and biotic components.

What is the primary characteristic of the O Horizon in a soil profile?

• Lacks nutrients

• Rich in organic material

• High mineral content

• Predominantly bedrock

Which process involves organisms moving materials within the soil without changing their state?

• Biological mixing

• Nutrient cycling

• Leaching

• Weathering

What is leaching in the context of soil systems?

• The erosion of soil particles

• The mixing of organic material

• The downward loss of nutrients

• The upward movement of minerals

Which transformation in soil involves the breakdown of organic matter into simpler compounds?

• Decomposition

• Weathering

• Biological mixing

• Leaching

What role do bacteria play in the nitrogen cycle within soil?

• They fix nitrogen into nitrates

• They decompose organic matter

• They cause soil erosion

• They increase mineral content

Which soil particle is the largest and allows for good drainage?

• Clay

• Silt

• Humus

• Sand

How is a soil texture triangle used?

• To measure soil temperature

• To determine soil color

• To show the ratio of sand, silt, and clay

• To calculate soil pH

Why is it important to view soils as systems in environmental studies?

• To ignore the biotic components

• To focus solely on the abiotic components

• To understand the interactions of inputs, outputs, and transformations

• Because they are static and unchanging

What are the abiotic components of a soil ecosystem?

• Rodents and moles

• Air, water, and mineral content

• Organic matter and humus

• Fungi and bacteria

Which soil particle type is known for retaining water and becoming waterlogged?

• Sand

• Clay

• Gravel

• Silt