Soil Quality

7-4.4 Explain the effects of soil quality on the characteristics of an ecosystem.

INTRODUCTION

• Soil is one of the most valuable abiotic factors in an ecosystem because everything that lives on land depends directly/indirectly on soil.

• Soil effects types of plants that can grow in an ecosystem which directly impacts the types of other organisms that can live there.

• If the soil quality changes in any of its properties, the ecosystem will also change.

SOIL QUALITY• Based on qualitative properties that

can be observed• Such as:

– soil profile– composition

– texture– particle size

SOIL PROFILE• Each layer is called a

horizon

• Label the Horizons from theWord Bank below…– Bedrock– Parent Material– Subsoil– Topsoil

Horizon A aka Horizon A aka

Horizon B aka Horizon B aka

Horizon C akaHorizon C aka

Horizon D akaHorizon D aka

Label the horizons

Organic LayerOrganic Layer

SOIL PROFILE• Top Soil

–Nutrient rich layer most suitable for the growth of plants

–Contains a mixture of:• clay• humus (decayed organic material)• minerals

SOIL PROFILE• Subsoil

– Area where groundwater can collect and flow

– Lighter in color because mostly made up of minerals such as sand, pebbles, clay or silt

– Minerals from the topsoil layer gradually make their way down into the subsoil

• because they are heavier than decomposing organic matter higher up the soil profile.

– The thickness of subsoil layers varies widely but it's usually deep enough to cover the root systems of large shrubs and trees.

SOIL PROFILE• Parent Material

– formed of small rocks and large stones or pebbles.

– usually free of plant and tree root systems

• Bedrock– solid rock that is gradually

weathered and broken up to produce the mineral content of the soil layers sitting above it

– depth of the bedrock varies by location, and in some areas the bedrock is exposed above ground level

• Bedrock is usually found between 5 feet and hundreds of feet below the topsoil horizon.

• Litter (dead stuff on top) decomposes into more humus

• Litter Humus

SOIL COMPOSITION• Composition =

– what makes up the soil• Mixture of:

– air– water– rock particles/minerals– humus:

• decayed organic material• makes soil more fertile• organic- anything that is or was

aliveWhat does the zig-zag between air and water mean?

“OM”= Humus, Decayed organic material

SOIL COMPOSITION• What does weathered mean?

– Broken down by wind, rain, ice, gravity, heat, pressure, chemicals

• Weathered bedrock material provides what three things in soil?

–sand–silt–clay

The combination of these materials in soil determine the soil type and affects the type of plants and animals that can grow/live in it.

SOIL COMPOSITION

• Other things that can affect soil components include:–type of plants–climate–time–slope of the land

SOIL TEXTURE• Texture depends

on the SIZE and PROPORTION of particles.

• Texture names are based on the % of:–SAND, SILT, CLAY

• Texture names include:– LOAM

• *garden, little sand– SANDY CLAY LOAM– SILT LOAM– CLAY– SAND

• Soil texture affects the amount of WATER absorbed – Which affects use by

plants and animals

As water empties from a mountain stream, its velocity starts to decrease. The largest size particles, like sand, are the first to drop out of suspension (Site A). Fine, clay size particles can be carried further away from the base of the slope before they are deposited. As a result, coarse textured soils tend to be found near the base of the mountain and fine textured soils are located further away (Site C).

SOIL PARTICLE SIZE

• Particles- soil “parts”• Effects how fast water

can move through or be absorbed and used–Aka soil permeability

Soil Components Separated

If this soil sample is 50% sand, 30% silt, and 20% clay, what soil texture is it? Use the Soil Textural Triangle.

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Soil Quality is based on:

• Permeability • pH

Permeability & Porosity• Permeable

– How freely water flows in soil

– Calculate the rate of drainage

• Porosity– Open air spaces (PORES) in soil– The higher the porosity, the

less or more permeable?

Soil Descriptions

pH• good soil pH is

between 4 and 10• Plants enjoy

pH 5 to 7

• Regardless of the nutrients present in the soil, if the pH is not suitable those nutrients will be inaccessible to the organisms

• LIME can be a fertilizer that can alter pH to make the nutrients more accessible– added to make more basic – (brings pH up or down?)

Farmer Tackett took a pH soil sample in 9 evenly spaced plots as shown below. Place a smiley face in Soil Plots where you predict plants would best grow, and a frown face in Soil Plots where you think plants would grow the least.

6 8 95 7 83 5 6

1. According to the soil profile, in which layer are most of the soil’s nutrients most likely found? ____

2. What layer is called parent material? ____

3. What layer is called bedrock? ____

4. What layer is called subsoil? ____

A B C DA B C DWhich rock type is the:

1. most permeable (rapid flow of water passing through)? _____2. least permeable (slowest flow of water passing through)? ___3. moderately permeable? ______

1. Which of these things is a primary ingredient of humus?A) Dead plant materialB) MineralsC) MetalsD) Rocks from earth’s crust 2. What effect do plants’ roots have on rock?A) They break it apartB) They cause to to undergo chemical changeC) They hold it togetherD) They weather it3. Why is topsoil darker than other levels of soil?A) It contains all the darker-colored mineralsB) It contains bits of burned treesC) It contains more organic matterD) It contains volcanic rock