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33 Cards in this Set

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aerosols
Solid, liquid, or gaseous particles suspended in the atmosphere.
atmospheric deposition
The movement of particulate and dissolved matter from the atmosphere into ecosystems by gravity or in precipitation.
biogeochemistry
The study of the physical, chemical, and biological factors that influence the movements and transformations of chemical elements.
biological crust
A soil crust composed of a mix of species of cyanobacteria, lichens, and mosses; also called a cryptobiotic or cryptogamic crust.
catchment
The area in a terrestrial ecosystem that is drained by a single stream; a common unit of study in terrestrial ecosystem studies; also called a watershed.
cation exchange capacity
A soil’s ability to hold nutrient cations such as Ca²⁺, K⁺, and Mg²⁺ and exchange them with the soil solution, determined by the clay content of the soil.
chemical weathering
The chemical breakdown of soil minerals leading to the release of soluble forms of nutrients and other elements. Compare mechanical weathering.
clays
Fine soil particles (< 2 μm) that have a semicrystalline structure and weak negative charges on their surfaces that can hold onto cations and exchange them with the soil solution.
decomposition
The physical and chemical breakdown of detritus by detritivores for energy capture, leading to the release of nutrients as simple, soluble organic and inorganic compounds that can be taken up by other organisms.
denitrification
A process by which certain bacteria convert nitrate (NO₃⁻) into nitrogen gas (N₂) and nitrous oxide (N₂O) under anoxic conditions.
eutrophic
Nutrient-rich; characterized by high primary productivity. Compare oligotrophic.
eutrophication
A change in the nutrient status of an ecosystem from nutrient poor to nutrient rich; such a change may occur naturally in some lakes due to the accumulation of sediments, but it may also be caused by anthropogenic nutrient inputs.
horizons
Layers of soil distinguished by their color, texture, and permeability.
lignin
A structural compound that strengthens plant tissues.
litter
Fresh, undecomposed organic matter.
loess
Thick layers of sediment deposited by wind.
mean residence time (turnover rate)
The amount of time an average molecule of an element spends in a pool, such as a plant or the soil, before leaving it.
mechanical weathering
The physical breakdown of rocks into progressively smaller particles without a chemical change. Compare chemical weathering.
mesotrophic
Having a nutrient status that is intermediate between oligotrophic and eutrophic, usually used in reference to lakes.
mineralization
The chemical conversion of organic matter into inorganic nutrients.
nitrification
A process by which certain chemoautotrophic bacteria, known as nitrifying bacteria, convert ammonia (NH₃) and ammonium (NH₄⁺) to nitrate (NO₃⁻) under aerobic conditions.
nitrogen fixation
The process of taking up nitrogen gas (N₂) and converting it into chemical forms that are more chemically available to organisms.
nitrogenase
A nitrogen-fixing enzyme found only in certain bacteria.
nutrient
A chemical element required by an organism for its metabolism and growth.
nutrient cycling
The cyclic movement of nutrients between organisms and the physical environment.
occlusion
A process by which soluble phosphorus combines with iron, calcium, and aluminum to form insoluble compounds that are unavailable as nutrients.
oligotrophic
Nutrient-poor, characterized by low primary productivity.
parent material
The rock or mineral material broken down by weathering to form a soil; usually the bedrock underlying the soil.
pool
The total amount of a nutrient or other element found within a component of an ecosystem.
sand
The coarsest soil particles
(0.05–2 mm).
soil
A mix of mineral particles, detritus, dissolved organic matter, water containing dissolved minerals and gases (the soil solution), and organisms that develops in terrestrial ecosystems.
till
Thick layers of sediment deposited by glaciers.
weathering
The physical and chemical processes by which rock minerals are broken down, eventually releasing soluble nutrients and other elements.