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Term Term description

Constant streamline flow of fluid or gas with no disruption or later mixing; not turbulent..

land grab

The contentious issue of large-scale land acquisitions: the buying or leasing of large pieces of land in developing countries by domestic and transnational companies, governments, and individuals.

land ice

Land ice includes any form of ice that lasts longer than a year on land, such as mountain glaciers, ice sheets, ice caps and ice fields (both similar to but smaller than an ice sheet), and frozen ground or permafrost. The result of melting land ice includes rising sea levels, long-term decline in fresh water resources, short-term increase in flash floods and accelerated warming from decreased albedo reflectance.

Law of Conservation of Mass

The principle that matter can neither be created nor be destroyed. Matter can be changed from one form into another, substances can be chemically or physically decomposed, but the total amount of mass remains the same .

Laws of Thermodynamics

Any of three principles governing the relationships between different forms of energy.


(In regards to a mountain) the side that is not exposed to wind and weather; on the leeward side of a mountain it is relatively dry and warm.


lentic systems

Still fresh water systems, can range from small, temporary rainwater pools a few inches deep to ponds of various sizes and depth to the largest and deepest lakes any where on earth.


Large order of scaly-winged insects, including the butterflies, skippers, and moths; adults are characterized by two pairs of membranous wings and sucking mouthparts, featuring a prominent, coiled proboscis.

light soils

Soils with a high percentage of large sand particles and characterized by rapid water infiltration and percolation, high soil aeration, but low water holding capacity. Light soils (sands and loamy sands) lend themselves to management practices designed to reduce soil salinity by leaching salts from the soil with applications of excess, low-salt irrigation water.

light-dependent reactions

The stage of photosynthesis during which light energy is absorbed by chlorophyll and transformed into chemical energy stored in ATP.

light-independent reactions

The stage of photosynthesis involving the reduction of carbon dioxide and the dissociation of water, using chemical energy stored in ATP: does not require the presence of light.


A complex organic compound that binds to cellulose fibers and hardens and strengthens the cell walls of plants. It is the chief noncarbohydrate constituent of wood.

limiting nutrient

The nutrient in short supply relative to the others will be exhausted first and will thus limit cellular growth. The other ingredients may play various roles such as exhibiting toxicity or promoting cellular activities, but there will not be an acute shortage to restrict growth as in the case of the limiting nutrient becoming exhausted. The usual way of determining which nutrient is limiting is to increase the concentration of one nutrient. If there is no effect, some other nutrient is limiting.


Any of various substances that are soluble in nonpolar organic solvents (as chloroform and ether), that are usually insoluble in water, that with proteins and carbohydrates constitute the principal structural components of living cells, and that include fats, waxes, phosphatides, cerebrosides, and related and derived compounds.


The geologic process through which unconsolidated materials are converted into solid rock, as by compaction or cementation. Sedimentary rocks are the simplest example of lithification.


The lithosphere, which is about 100 kilometers (60 miles) deep in most places, includes the brittle upper portion of the Earth's mantle and the crust. The movement of the lithosphere, called plate tectonics, is the reason behind a lot of Earth's most dramatic geologic events. When one plate moves beneath another, or when two plates rub together, they can create earthquakes, volcanoes and mountain ranges.

Little Ice Age

A period between about 1300 and 1870 during which Europe and North America were subjected to much colder winters than during the 20th century.


A soil with roughly equal proportions of sand, silt, and clay.

long wave infrared radiation

A type of long-wave radiation that extends from the red edge of the visible spectrum. Earth emits longwave radiation because Earth is cooler than the sun. When solar radiation reaches Earth the ground heats up and re-emits energy as longwave radiation in the form of infrared rays.

lotic systems

Flowing water systems that can range in size from a spring that is only a few centimeters wide to a major river that is miles in width and thousands of miles long.

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