4.10 sg
Introduction
Overview of the importance of soils and watersheds.
Page 2: Soils as Ecosystems
Soil Definition: A renewable resource developing gradually through the weathering of rocks and organic material accumulation.
Topsoil Accumulation: Slow process (~1 mm/year under ideal conditions).
Management: Careful practices can renew soil indefinitely.
Erosion Impact: Most practices deplete soil, with severe erosion rates reaching over 25 mm/year.
Page 3: Components of Soil
Total Components: Six main components of soil:
Sand and gravel
Silts and clays
Dead organic material
Soil fauna (organisms) and flora (plants)
Water
Air
Page 4: Variations in Soil Composition
Soil Types: Variations in the six components lead to diverse soil types.
Soil Texture: Amounts of sand, silt, and clay are crucial characteristics.
Loam Soils: Best for agriculture due to a balanced mixture.
Brazilian Tropical Soils: Weathered red clays with low nutrients and water retention.
Central US Black Soils: Nutrient-rich with good water retention properties.
Pages 5-6: Soil Texture
Granule Sizes:
Sand: 0.05 - 2mm
Silt: 0.02 - 0.05mm
Clay: <0.02 mm
Soil Texture Pyramid: Visual representation of soil texture proportions.
Page 7: Grassland vs. Tropical Rainforest Soil
Comparison of soil characteristics between different ecosystems.
Page 8: Soil Fauna and Fertility
Decomposition Process: Bacteria, algae, and fungi recycle nutrients from litter.
Soil Diversity: One gram can contain hundreds of bacteria and vast fungal networks.
Worms and Insects: Aid in processing organic material, aerating the soil.
Mycorrhizal Symbiosis: Partnership between plant roots and fungi improving nutrient uptake.
Page 9: Soil Ecosystem Diversity
Overview of various soil organisms contributing to soil health.
Pages 10-11: Soil Horizons
Soil Layers: Horizontal layers called horizons make up a soil profile.
Types of Horizons:
O Horizon: Organic layer with leaf litter and organisms
A Horizon: Surface soil with minerals and organic material
E Horizon: Leached of nutrients
B Horizon: Denser subsoil
C Horizon: Weathered rock fragments
Page 12: Soil Types and Composition
Soil Variability: Different soils have unique layers influencing their productivity (e.g., temperate deciduous, forest, grassland).
Page 13: Importance of A Horizon
Key Soil Types:
Mollisols: Thick organic-rich A-Horizon prevalent in farmland.
Alfisols: Thinner A-Horizon, less organic material, also significant for agriculture.
Page 14: Watersheds
Water Behavior: After precipitation, water may evaporate, percolate to groundwater, or runoff into streams.
Watershed Definition: Area of land catching and draining water into a specific body of water.
Pages 15-17: Watershed Examples
Mapping: Various watersheds including Lake Erie and Ohio River with visual aids.
Page 18: Factors Affecting Watershed Quality
Elevation: High points create watershed boundaries.
Pollution Sources: Activities like road runoff, pesticide use, and sewage impact water quality downstream.
Impermeable Surfaces: Increase runoff and pollution risk.
Page 19: Storm Drains and Wastewater Treatment
Pollution Flow: Stormwater runoff is untreated, in contrast to treated wastewater from sewer systems.
Sewage Treatment Processes: Overview of how wastewater is processed versus stormwater.