Soil Processes and Accumulation Quiz

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

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.