Ecosystems:

1
Chapter 3

• Ecosystems
• What Are They and
• How Do They Work?

2
SOIL A RENEWABLE RESOURCE

• Soil is a complex mixture of
• Eroded rock
• Mineral nutrients
• Decaying organic material
• Water
• Air
• Billions of living organisms most of them are
  microscopic decomposers

3
SOIL A RENEWABLE RESOURCE

• Soil is a renewable resource, but it is
  renewed very slowly.
• Depending on the climate, the formation of 1 cm
  of soil could take from 15 to 100 yrs.

4
Figure 3-23
5
SOIL A RENEWABLE RESOURCE

• Soil is the base of all life on land.
• The nutrients that are passed on from producers
  to consumers come from the soil.
• Human agricultural activities greatly accelerate
  natural soil erosioncould make it a nonrenewable
  resource.

6
Layers in Mature Soils

• Mature soils are arranged in a series of
  horizontal layers called soil horizons.
• O Horizon (surface litter layer) leaves, twigs,
  and other organic materials
• A Horizon (topsoil) composed of mostly of humus
  partially decomposed organic matter
• B Horizon (subsoil) mostly inorganic material
  like rock pieces, sand, and clay with small
  amounts of organic matter from the A Horizon
• C Horizon (bedrock) the unweathered parent
  material

7
Layers in Mature Soils
8
Layers in Mature Soils

• Infiltration the downward movement of water
  through soil.
• Leaching dissolving of minerals and organic
  matter in upper layers carrying them to lower
  layers.
• The soil type determines the degree of
  infiltration and leaching.

9
Soil Types

• Most cropland is on soil that was exposed by the
  clearing of grasslands or deciduous forests.
• There are as many as 15,000 different types of
  soil in the U.S. alone.

10
Soil Profiles of the Principal Terrestrial Soil
Types
Figure 3-24
11
Soil Properties

• The large variety of soils is a result of the
  large variety of the different combinations of
  soil properties
• Soil Texture
• Particle size
• Moisture content
• Organic matter
• Bulk Density
• Fertility N,P,K, pH
• Porosity / Permeability