Soils

Microenvironments

Aboveground environment

Microclimate

Edaphic factors – soil environment

Belowground environment

Definitions of SOIL

“Typical” soil composition

Geologic definition: Loose surface of the earth as distinguished from solid bedrock (support of plant life not required).

Air 25%

Traditional definition: Material which nourishes and supports growing plants (i l d rocks, (includes k water, t snow, air). i)

Mineral Matter 45%

Water 25%

Component definition: Mixture of mineral matter, organic matter, water, and air. Combined definition: Loose material on the Earth’s surface supporting plant life that is composed of a mixture of mineral and organic matter, water, and air.

Organic Matter 5%

How would you expect this to be different for a wetland soil ?

Typical soil horizons:

Typical soil horizons:

a result of soil development

a result of soil development

Soil development results from an interaction of:

O Horizon: Organic matter: litter & humus

• Weathering of parent material (climate, type of parent material, vegetation) • Input of transported material and/or loss of on-site material

Litter

• Organic matter input (vegetation) • Soil biota actions Parent material Biota Climate

Humus Soil development Parent material

Parent material

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Typical soil horizons:

Typical soil horizons:

a result of soil development

a result of soil development

A Horizon:

E Horizon:

Nutrient-rich soil layer

A leached layer sometimes present below the A horizon (Fe, Al removed) A horizon

Thin A horizon in forest soil

E horizon B horizon

Thicker A horizon in grassland soil

Parent material

Typical soil horizons:

Typical soil horizons:

a result of soil development

a result of soil development

B Horizon:

C Horizon:

Nutrient-poor soil layer

Soil layer dominated by parent material

B horizon in forest soil

B horizon in arid zone soil

C horizon in forest soil

Parent material

Parent material

Selected Soil Edaphic Factors • Texture

Physical or chemical attribute of soil that impacts plant function

• Structure • Organic Matter • Moisture content & availabilityy • pH

Selected Soil Edaphic Factors Soil Texture Particle size attributes Texture Particle size range category (mm diameter) Clay

< .002

Silt

.002 - .05

Sand

.05 – 2.0

Gravel

> 2.0

• Aeration • Nutrients 9“available” 9nutrient holding capacity (CEC)

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SOIL TEXTURE CLASSES Selected Soil Edaphic Factors Clay soils: Fine textured

Soil Texture Particle size composition Texture class

Particle size range (mm diameter)

Clay

< .002

Silt

.002 - .05

Sand

.05 – 2.0

Gravel

> 2.0

Soils have varying proportions of these particles

Silty soils: Intermediate textured

The relative proportions of different particles place p a soil into a sized p certain SOILTEXTURE CLASS

Sandy soils: Coarse textured Loam soils: Balanced texture

% Sand

USDA Soil Texture Triangle

SOIL TEXTURE CLASSES Selected Soil Edaphic Factors Soil Texture Determining a texture class: 70% silt

Particle size composition

Effects of soil texture

Texture class

Particle size range (mm diameter)

• Water holding capacity

15% clay

Clay

< .002

• Aeration

15% sand

Silt

.002 - .05

Sand

.05 – 2.0

• Temperature T t

Gravel

> 2.0

• Nutrients • Erosion

The intersection is the texture class: Silt loam

% Sand

USDA Soil Texture Triangle

Selected Soil Edaphic Factors Soil Structure

Selected Soil Edaphic Factors Soil Structure

G ra n u la r

Effects of soil structure

G ra n u la r

B lo c k y (S u b a n g u la r)

B lo c ky

(A n g u la r)

(S u b a n g u la r)

(A n g u la r)

• Water movement • Root growth

P la ty

• Erosion E i / slope l stability t bilit

P la ty P ris m a tic

P ris m a tic

C o lu m n a r

C o lu m n a r

W edge

W edge

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Selected Soil Edaphic Factors Soil organic matter Effects of soil OM

Soil pH

Selected Soil Edaphic Factors Soil bulk density

Effects of soil pH

Soil surface hardness

Effects of soil bulk density

Effects of surface hardness

• Nutrient input

• Soil organism / plant function

• aeration

• Water infiltration

• Moisture retention

• Nutrient cycling & retention

• Water retention and flow

• Seed incorporation / germination

Soil moisture

Soil aeration

Effects of soil H2O

Soil water infiltration

Effects of soil aeration

Effects of soil H2O infiltration

• Organism function

• Soil organism / plant function

• Moisture input to soil

• Aeration

• Nutrient cycling & retention

• Water availability to organisms

• Nutrient cycling

Other Soil Properties Often Assessed • Color

Regional Soils Tremendous Soil Variation across WA

• Horizon development / descriptions

• Variation in parent material

• Soil macrofauna

• Variation in climate

• Soil microorganisms g

• Variation in plant communities Greatest variation on east slope of Cascades & Olympics

Regional Soils

Regional Soils Glacial Outwash

Puget Sound Area • Glacial deposits 9Glacial till (e.g., “Alderwood” series) 9Glacial outwash (e.g., “Everett” series)

Lacustrine clays Glacial till Lacustrine clays

Development under coniferous forests ¾ Acidic conditions, low temperatures = slow development

Puget Sound Area • Glacial deposits 9Glacial till (e.g., “Alderwood” series) 9Glacial outwash (e.g., “Everett” series)

• Old sedimentary deposits • Wetland mucks

Springs & slides ¾ Interbedding of (1) clay and (2) sand layers with glacial till

• Alluvial soils

can lead to (1) springs and (2) slope instability

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Soil Measurements Today For each group: Field measurements today Soil horizon descriptions (1 / site)

Later lab analyses on collected soil pH

Soil Measurements Thursday Measurements by EACH group Use same vegetation stands as we used for the forest vegetation lab Red alder – sword fern

W. hemlock – sword fern Soil water infiltration (4x)

Litter type and depth, humus depth (4 / site) Organic matter content Soil texture class (4 / site)

Moisture

Surface hardness (4 / site)

Texture

Soil infiltration rate (4 / site)

Bulk density

Litter & humus (4x) Surface hardness (10x)

Soil horizon description (1 x)

Soil texture class (4x)

Soil Collection Thursday • Six soil tins from each site – collected by bulk density corer 9 5 – 15 cm deep (A horizon) • Four 1-liter bulk samples in paper bags (labeled) 9 5 – 15 cm deep p

These samples will be used next week to assess • Soil moisture

• Soil pH

• Soil bulk density

• Soil texture

• Soil OM

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