Definitions chapter 4: The terrestrial environment

Question 1

Water Balance

Answer 1

Maintenance of the balance of water between organisms and their surrounding environment

Question 2

Leaf Area Index (LAI)

Answer 2

The total leaf area of a plant exposed to incoming light energy relative to the ground surface area beneath the plant

Question 3

Regolith

Answer 3

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

Question 4

Mechanical Weathering

Answer 4

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)

Question 5

Parent Material

Answer 5

The material from which soil develops

Question 6

Leaching

Answer 6

Dissolving and washing of nutrients out of soil, litter, and organic matter

Question 7

Soil Profile

Answer 7

Distinctive layering of horizons in the soil

Question 8

Horizon

Answer 8

Major zone or layer of soil, with its own particular structure and characteristics

Question 9

O Horizon

Answer 9

Surface stratum of mineral soil, dominated by organic material and consisting of undecomposed or partially decomposed plant materials, such as dead leaves

Question 10

A Horizon

Answer 10

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

Question 11

B Horizon

Answer 11

Soil stratum beneath the A horizon, characterized by an accumulation of silica, clay, and iron and aluminum oxides, and possessing blocky or prismatic structure

Question 12

C Horizon

Answer 12

Soil stratum beneath the solum (A and B horizons), little affected by biological activity or soil-forming processes

Question 13

E Horizon

Answer 13

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

Question 14

Saturation

Answer 14

The state of a soil when the water content is greater than the pore space can hold

Question 15

Field Capacity

Answer 15

Amount of water held by soil against the force of gravity

Question 16

Capillary Water

Answer 16

That portion of water in the soil held by capillary forces between soil particles

Question 17

Available Water Capacity

Answer 17

Supply of water available to plants in a well-drained soil

Question 18

Laterization

Answer 18

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

Question 19

Calcification

Answer 19

Process of soil formation characterized by accumulation of calcium in lower horizons

Question 20

Salinization

Answer 20

The process of accumulation of soluble salts in soil, usually by upward capillary movement from a salty groundwater source. Also called salination

Question 21

Podzolization

Answer 21

Soil-forming process in which acid leaches the A horizon and iron, aluminum, silica, and clays accumulate in lower horizons

Question 22

Gleization

Answer 22

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