Definitions chapter 4: The terrestrial environment Flashcards
Water Balance
Maintenance of the balance of water between organisms and their surrounding environment
Leaf Area Index (LAI)
The total leaf area of a plant exposed to incoming light energy relative to the ground surface area beneath the plant
Regolith
The unconsolidated debris layer composed of exposed rock overlaying the hard, unweathered rock in most places on the Earth’s surface. It varies in depth from virtually nonexistent to tens of meters
Mechanical Weathering
Breakdown of rocks and minerals in place by disintegration processes such as freezing, thawing, and pressure that do not involve chemical reactions (also referred to as physical weathering)
Parent Material
The material from which soil develops
Leaching
Dissolving and washing of nutrients out of soil, litter, and organic matter
Soil Profile
Distinctive layering of horizons in the soil
Horizon
Major zone or layer of soil, with its own particular structure and characteristics
O Horizon
Surface stratum of mineral soil, dominated by organic material and consisting of undecomposed or partially decomposed plant materials, such as dead leaves
A Horizon
Surface stratum of mineral soil, characterized by maximum accumulation of organic matter, maximum biological activity, and loss of such materials as iron, aluminum oxides, and clays
B Horizon
Soil stratum beneath the A horizon, characterized by an accumulation of silica, clay, and iron and aluminum oxides, and possessing blocky or prismatic structure
C Horizon
Soil stratum beneath the solum (A and B horizons), little affected by biological activity or soil-forming processes
E Horizon
Mineral horizon characterized by the loss of clay, iron, or aluminum, and a concentration of quartz and other resistant minerals in sand and silt sizes; light in color
Saturation
The state of a soil when the water content is greater than the pore space can hold
Field Capacity
Amount of water held by soil against the force of gravity
Capillary Water
That portion of water in the soil held by capillary forces between soil particles
Available Water Capacity
Supply of water available to plants in a well-drained soil
Laterization
Soil-forming process in hot, humid climates, characterized by intense oxidation; results in loss of bases and in a deeply weathered soil composed of silica
Calcification
Process of soil formation characterized by accumulation of calcium in lower horizons
Salinization
The process of accumulation of soluble salts in soil, usually by upward capillary movement from a salty groundwater source. Also called salination
Podzolization
Soil-forming process in which acid leaches the A horizon and iron, aluminum, silica, and clays accumulate in lower horizons
Gleization
A process in waterlogged soils in which iron, because of an inadequate supply of oxygen, is reduced to a ferrous compound, giving dull gray or bluish mottles and color to the horizons
