Soil Processes and Accumulation Quiz

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Questions and Answers

What type of earthworm is an epi-endogeic species?

Nightcrawler

Red earthworm (correct)

Earth feeder

Peregrine soil dweller

Which type of decomposition process occurs after about ⅔ of organic carbon is left?

Slow stage decomposition (correct)

Aerobic decomposition

Facultative anaerobic decomposition

Fast stage decomposition

Which factor is NOT mentioned as affecting the rate of decomposition?

Moisture content

Substrate composition

Soil pH (correct)

Temperature

What role do fungi and actinomycetes play in microbial conversion?

Organic carbon decomposition Signup and view all the answers

What is the primary purpose of leaching in soil processes?

To remove water-soluble compounds from the soil Signup and view all the answers

Which type of anaerobe may require oxygen to survive?

Facultative anaerobe Signup and view all the answers

Which statement best describes heterotrophic bacteria?

They feed on organic carbon sources. Signup and view all the answers

Which of the following best describes fragmentation in the decomposition process?

It converts larger organic materials into smaller pieces. Signup and view all the answers

What is the primary purpose of decomposition models mentioned?

To estimate carbon loss Signup and view all the answers

What is the role of saprophytic fungi in decomposition?

To break down complex carbohydrates and help in humus formation. Signup and view all the answers

Which layer of soil is primarily affected by airborne ascomycetes?

Oi Layer Signup and view all the answers

Which of the following is NOT a type of earthworm classified under the given categories?

Mesophilic Signup and view all the answers

What results from the action of earthworms in soil?

Formation of mull humus and improved soil structure Signup and view all the answers

What role does condensation/humidification play in soil composition?

It alters the physical and chemical properties of soil. Signup and view all the answers

Which organisms are primarily responsible for breaking down hemicellulose and cellulose?

Termites and some fungi Signup and view all the answers

What are the effects of higher molecular weight carbon compounds on soil?

Enhance soil structure and increase water holding capacity Signup and view all the answers

Which layer in the decomposition process is characterized by the presence of Penicillium and Trichoderma?

Oe Layer Signup and view all the answers

What is the outcome of pathogen invasion on leaves or needles that remain on the tree?

Disruption of cell integrity and wall breakdown Signup and view all the answers

What is one of the primary functions of tree roots in relation to soil?

Creating channels that improve soil porosity Signup and view all the answers

How do fine roots contribute to organic matter (OM) concentration compared to leaf litter production?

Fine roots have an annual production that exceeds leaf litter production. Signup and view all the answers

Which statement reflects the nutrient uptake and recycling role of trees?

Trees utilize nutrients for foliage, converting them into forest litter. Signup and view all the answers

What is a key factor that enhances the stability of soil slopes?

Heavy vegetation and deep-root systems Signup and view all the answers

What does the term 'nutrient pumping theory' refer to?

The process of trees taking up and recycling nutrients from the soil Signup and view all the answers

In areas of poor fertility, what percentage of total production is attributed to fine roots?

50% Signup and view all the answers

What is the primary characteristic of podzolization?

Translocation of organic materials and sesquioxides Signup and view all the answers

What role does humus play as a binding agent in soil stability?

Humus acts as a temporary binding agent, affecting stability. Signup and view all the answers

What does leaching refer to in soil science?

The removal of materials in solution from the soil Signup and view all the answers

Which horizon is characterized by maximum illuviation?

B Horizon Signup and view all the answers

Which of the following best describes the function of roots in soil morphology?

Roots stabilize soil and prevent erosion. Signup and view all the answers

Which process leads to the formation of an oxic horizon?

Desilication Signup and view all the answers

What does melanization refer to in soil processes?

The darkening of light-colored minerals Signup and view all the answers

What is salinization?

The accumulation of salts in soil Signup and view all the answers

What is the primary effect of decalcification in soil?

Leaching of carbonates from the soil Signup and view all the answers

What characterizes the E horizon in soil profiles?

Maximum eluviation of materials Signup and view all the answers

Which soil order is typically associated with high organic matter content?

Mollisols Signup and view all the answers

Which process involves the churning of soil materials by biological or physical means?

Pedoturbation Signup and view all the answers

What is desalinization in soil science?

The process of removing soluble salts Signup and view all the answers

Which soil order is typically found in desert regions?

Aridisols Signup and view all the answers

Which process describes the reduction of iron in anaerobic soils?

Gleization Signup and view all the answers

Which soil order is characterized by high clay content and poor drainage?

Vertisol Signup and view all the answers

What is a primary function of fine roots in plants?

Water and nutrient uptake Signup and view all the answers

What type of root structure is characterized by numerous laterals that extend down from the base of the stump?

Sinker root Signup and view all the answers

Which of the following statements accurately describes mycorrhizae?

They are essential for the life cycle of most fungi. Signup and view all the answers

How is the depth of the rooting system generally characterized?

Typically found at 0-60 cm depth Signup and view all the answers

What type of mycorrhiza penetrates the root cortex of plants?

Endomycorrhizae Signup and view all the answers

What effect can potting medium rich in phosphorus have on plant growth related to mycorrhizal roots?

Negatively affects growth Signup and view all the answers

Which root form is described by having a strong, developed tap root along with lateral roots near the root collar?

Tap roots Signup and view all the answers

What is one of the main components of the mycorrhizal relationship that benefits plants?

Enhanced absorptive surface area of roots Signup and view all the answers

What factor can significantly influence the competition among tree roots?

Water, nutrients, light, and space Signup and view all the answers

What is the characteristic of ectomycorrhizae?

They form a Hartig net. Signup and view all the answers

Study Notes

OM Accumulation

Leaching: Removal of materials in solution from the soil by percolating water
Calcification: Accumulation of carbonates, usually in desert areas, leaving a white powdery appearance
Decalcification: The eluviation of carbonates
Salinization: Accumulation of salts
Desalinization: Leaching of soluble salts
Alkalization: Accumulation of sodium
Dealkalization: Removal of sodium
Melanization: Darkening of light-colored minerals by the admixture of organic matter
Leucinization: Paling of soil horizons due to the disappearance of dark organic materials
Gleization: Reduction of iron under anaerobic, waterlogged conditions, with the production of bluish-greenish gray matrix color
Pedoturbation: Biological and/or physical churning and cycling of soil materials
Podzolization: Translocation of organic materials and sesquioxides from the upper soil horizon to the B horizon, creating a spodic horizon
Desilication (Laterization): Removal of silica leading to the concentration of iron as ferric oxides under oxidizing conditions, forming laterite, an iron-rich subsoil layer in highly weathered humid tropical soils

Soil Orders

Entisol: Young soils with little development
Inceptisol: Slightly developed soils
Alfisol: Moderately weathered soils with a good balance of nutrients
Ultisol: Highly weathered soils with low fertility
Oxisols: Extremely weathered soils found in tropical climates
Spodosol: Soils with a spodic horizon, formed by podzolization
Histosol: Soils with a high organic matter content (at least 20% mineral matter)
Mollisols: Soils with a thick, dark topsoil, found in grasslands
Vertisol: Swelling and shrinking clay soils, often found in rice fields
Andisols: Soils formed from volcanic ash
Aridisols: Desert soils with low fertility, typically dry
Gelisols: Soils found in permafrost regions

Hans Jenny Equation: Soil = f(Cl O R P T)

Forest vegetation and soil covary
Global level: Influenced by climate
Regional and local level: Influenced by parent material and topography
Investigated with aerial photograph (stereoscope)

Boreal Forest

High latitude, northern hemisphere
Upper elevations of mountains
Dominated by species from Genera Picea, Abies, and Pinus, with hardwood species of Populus, Betula and Alnus

Mineral Soil

Decomposed by actinomycetes (break down cellulose and resistant materials)
Leaching: Movement/removal of water-soluble sugars, polyphenols, and organic acids, resulting in increased palatability
Fragmentation: Converting OM to smaller pieces by soil fauna, increasing surface area for bacteria and fungi colonization, speeding up decomposition

Forest Floor Decomposition

Complex web of interactions among soil fauna and microorganisms
Stages:
- Pathogen invasion: Occurs while leaves/needles are still on the tree, disrupting cell integrity
- Microbial conversion: Cellulose and carbohydrates are converted to CO2 and H2O, involving bacteria (heterotrophic, autotrophic, aerobic, anaerobic) and fungi (actinomycetes)
- Condensation/humidification: Concentration of resistant organics, leading to high molecular weight carbon compounds, affecting soil physical, chemical, and biological properties, thereby forming humus

Factors Affecting Rate of Decomposition

Substrate: High amounts of lignin and polyphenols = slow rate
Temperature: Affects organism activity
Moisture content: Affects organism activity through aeration and moisture supply

Tree Roots and their Significance

Interface between soil and plants
Influence soil properties
Alter morphology and micromorphology
Stabilize soil/slope: Prevent landslides and provide support
Microtopography: Creates root disks, affecting soil morphology
Concentration of OM: Annual production of fine roots exceeds leaf litter production
Nutrient uptake and recycling: The nutrient pumping theory
Formation of large continuous macropores: Increasing infiltration and soil by-pass contact
Weathering: Accelerated decomposition through root exudates

Characterizing Root System

Depth of rooting system: Typically shallow, uncommon to penetrate below 0.2 m depth
Components of root system:
- Structural roots: Large roots for stability and support
- Fine roots: 1-2 mm in diameter, responsible for water and nutrient uptake
Allometric Equation: Shows a general relationship between weight of individual tree components or between above and belowground biomass
Interaction of tree roots and other plants: Competition for water, nutrients, light, and space

Mycorrhiza

Symbiotic association between specific root-inhabiting fungi and fine feeder roots of plants
Types: Ectomycorrhizae, Endomycorrhizae
Naming: Based on the host plant

Benefits of Mycorrhizae to Plants

Increase absorptive surface of roots
Increase tolerance to stress (water, nutrients, disease)
Increase access to unavailable ions (bound P)
Deter infection by other fungi
Increase access to organic N sources
May negatively affect growth when soil is high in P

Benefits of Mycorrhizae to Fungi:

Most must form mycorrhizal association to complete their life cycle
Depend on photosynthate (carbohydrates and some vitamins) from plant host

Factors Affecting Mycorrhizal Development:

Soil type, pH, chemical composition
Climate, temperature, and moisture
Plant species and their genetic diversity

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Description

Test your knowledge on various soil processes like leaching, calcification, and podzolization. This quiz covers the intricate details of how materials accumulate and transform within soil profiles. Challenge yourself to identify the different processes affecting soil characteristics.