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7b4 Soils

Soils Composition & Significance

7b4 Soils
7b4 Soils

Soils Objectives

  • List the three basic components of topsoil.
  • Describe the composition and characteristics of different soil types.
  • Provide examples of organisms commonly found in soil food webs.
Earlier in the course we explored compost, including the role of detritivores & decomposers in producing soil from the remains of organisms.  In this section we focus on soil composition.
Soil is comprised of multiple layers.
7b4 Soils

Topsoil, like it sounds, is on top of other deeper layers.  Topsoil has the most interactions with wind, water, and organisms.  This is what we see and and frequently interact with in the garden.

This video introduces topsoil.
Topsoil is comprised of three components: minerals, organic matter (the remains of organisms), and living soil organisms.
7b4 Soils
7b4 Soils

You may have heard of “clay” and “sandy” soil or experienced them first-hand.  There are many names for soils, this video introduced some of the more common types.  Consider what you could do to improve each of the soil types for gardening.  What would you add to improve plant growth.

You may have a local soil that is unique because it has a higher concentration of a specific mineral.  In the Willamette Valley, we have a soil that tells a history of the valley’s formation.

 

Soil Organisms

Organisms are part of topsoil, and are their decomposing remains.  One of the easiest was to improve or “amend” soil for gardening or larger agricultural use is to add compost.

 
7b4 Soils
Soil organisms are critical in breaking the remains of other organisms into nutrients that can return to producers and reenter the food web.
From the earlier compost & decomposers section, what do we call the organisms that directly eat corpses, scat, or leaves, breaking them down into detritus?
From the earlier compost & decomposers section, what do we call the organisms that directly eat corpses, scat, or leaves, breaking them down into detritus?
What do we call the organisms that consume detritus, breaking it down into organic matter?
What do we call the organisms that consume detritus, breaking it down into organic matter?
Fungi and some bacterial species are _____ that can break the organic matter down into nutrient form, that can be reutilized by producers.
Fungi and some bacterial species are _____ that can break the organic matter down into nutrient form, that can be reutilized by producers.

When many people thing of soil organisms, earthworms pop into the mind.  Earthworm species are detritivores that move through soil, increasing aeration (oxygen availability) and soil fertility (available nutrients).  Earthworms are also an important food for many species.

 

Earthworms are more structurally complex than many people realize.  The castings (scat) produced by their digestive tract are a form of fertilizer.

 

Millipedes are arthropod detritivores, and although some species are small, some are quite large.  They are increasingly popular as pets.  A note is that some release a caustic and toxic substance when startled, so always wash your hands after handling.

 

Just in time for this module, our soil decomposers are popping up reproductive structures all over.These are most likely Amanita muscaria, they are pretty common here and often grow at the base of trees.

This is the end of the Habitat Guide.  Material from this guide and the Long-Term Guide will be assessed on the weekly quiz.
7b4 Soils
Check your knowledge.  Can you:
  • list the three basic components of topsoil?
  • describe the composition and characteristics of different soil types?
  • provide examples of organisms commonly found in soil food webs?
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