APES Unit 4.2 + 4.3 + 4.6 Soil and Watersheds

What is soil?

A mixture of geologic and organic components

What is humus?

The main nutrient-rich component of soil created by decomposed organic matter

What is weathering? How does it relate to soil formation?

Weathering is the physical, chemical, and biological breakdown of rocks. Weathering causes soil formation.

What is erosion?

The transport of weathered rock by wind/rain

What is deposition?

The depositing of weathered rocks in a new location

What three factors affect soil formation?

Parent Material, Climate, Topography

How does the parent material affect soil formation?

It determines the soil pH and the amount of nutrients present

How does the climate affect soil formation?

The warmer the temps, the faster organic matter will break down. The more precipitation, the more weather/erosion that will occur.

How does topography affect soil formation?

Steep slopes will create more erosion, level ground will create more deposition

What are the four soil horizons?

O, A, B, C

What is the O-Horizon?

The layer of organic matter on top of soil that provides nutrients and limits H2O loss to evaporation

What is the A-Horizon?

Also known as topsoil, it is a layer of humus and minerals that contains the most biological activity to break down organic matter

What is the B-Horizon?

Also known as subsoil, it is a lighter layer mostly made of minerals with little organic matter and some nutrients

What is the C-Horizon?

The least weathered soil layer that is the closest to the parent material

What are two ways that soil degradation can occur?

Loss of topsoil, Compaction

How can the loss of topsoil occur?

Tilling and a lack of vegetation can increase erosion

How can compaction occur?

Machines, grazing livestock, and humans who walk over soil make the soil more dense and unable to retain moisture which makes soil dryer and more prone to erosion

What three particles is soil made of, in order from largest to smallest particle size?

Sand, Silt, Clay

What is porosity? What types of soil particles affect porosity?

The amount of pore space a soil has, the more sand the more porosity, the more clay the less porosity

How does porosity affect soil?

It allows for water drainage, air flow, and nutrient availability

What is permeability?

How easily water drains through soil

What is H2O holding capacity?

How well soil retains water

How does porosity affect permeability? How does that affect H2O holding capacity?

The more porous, the more permeable, the more permeable, the lower the holding capacity

What are five factors that increase nutrients in soil?

Organic matter, humus, decomposer activity, clay, bases

What are four factors that decrease nutrients in soil?

Acid, excessive rain, excessive farming, topsoil erosion

What are factors that increase H2O Holding capacity?

Aerated soil, compost/humus, clay, root structure

What are factors that decrease H2O Holding capacity?

Compacted soil, topsoil erosion, sand, root loss

What is a watershed?

An area of land where all the water drains into a common outlet.

What are three factors that affect how watersheds drain?

Vegetation, soil composition, slope

What are four ecosystem services that estuaries/wetlands can provide?

Tourism revenue, water filtration, habitats for food sources, storm protection

What can cause eutrophication?

Nitrogen or Phosphorus pollution

What happens during eutrophication?

Algae blooms, which decreases the amount of sunlight reaching plants in shallow water which causes them to die, then bacteria use all the O2 in the area for decomposing the plants which leads to hypoxia and dead zones

How does clear cutting affect watersheds?

The loss of root structure causes more erosion, which deposits sediment in water, the lack of shade from trees also increases the temperature of the water

How does the deposition of sediments affect water?

It increases the temperature and turbidity of water