PhysicalGeography.net | GLOSSARY OF TERMS

Glossary of Terms: N

Native Species
Species that normally exists and reproduces in a specific region of the Earth. Compare with immigrant species, indicator species, and keystone species.

Natural Gas
Hydrocarbon based gas, mainly composed of methane, commonly found in the pores of sedimentary rocks of marine origin.

Natural Hazards
(1) Natural phenomena that produce negative effects on life.
(2) The study of the hazards of natural phenomena.

Ionizing radiation that comes from natural sources in the environment.

Natural Selection
Environment's influence on the reproductive success of individuals in a population. It results in the exclusion of maladapted genetic traits found within individuals in a population.

Neap Tide
Tide that occurs every 14 to 15 days and coincides with the first and last quarter of the moon. This tide has a small tidal range because the gravitational forces of the moon and Sun are perpendicular to each other. Contrasts with spring tide.

Needle Ice
A form of periglacial ground ice that consists of groups ice slivers at or immediately below the ground surface. Needle ice is about a few centimeters long.

Negative Feedback
Change in the state of a system that counteracts the measured effect of the initial alteration.

Balance between incoming and outgoing longwave radiation. Mathematically expressed as:

### L* = (LD- LU)

where L* is net longwave radiation at the surface,
LD is atmospheric counter-radiation (greenhouse effect) directed to the Earth's surface,
and LU is longwave radiation lost from the Earth's surface.

Net Primary Productivity
Total amount of chemical energy fixed by the processes of photosynthesis minus the chemical energy lost through respiration.

Balance between incoming and outgoing shortwave and longwave radiations. Mathematically expressed as:

### Q* = (K+k)(1 -a) - LU + LD

where Q* is surface net radiation (global annual values of Q* = 0, because input equals output, local values can be positive or negative),
K is surface direct shortwave radiation,
k is diffused shortwave radiation (scattered insolation) at the surface,
a is the albedo of surface,
LD is atmospheric counter-radiation (greenhouse effect) directed to the Earth's surface,
and LU is longwave radiation lost from the Earth's surface.

Balance between incoming and outgoing shortwave radiations. Mathematically expressed as:

### K* = (K+k)(1 -a)

where K* is surface net shortwave radiation,
K is surface direct shortwave radiation,
k is diffused shortwave radiation (scattered insolation) at the surface,
and a is the albedo of surface.

Neutral
Any substance with a pH around 7.

Neutral Atmosphere
Condition in the atmosphere where isolated air parcels do not have a tendency to rise or sink. The parcels of air tend to be same temperature as the air that surrounds them.

Neutralism
Interspecific interaction where the species do not directly influence each other fitness.

Neutral Solution
Any water solution that is neutral (pH approximately 7) or has an equal quantity of hydrogen ions (H+) than hydroxide ions (OH-). Also see acidic solution and basic solution.

Neutron
Atomic sub-particle found in the nucleus of an atom. This particle is similar in mass to a proton but does not have an electromagnetic charge.

Névé
Partially melted and compacted snow that has a density of at least 500 kilograms per cubic meter.

Newton
A unit of force that creates an acceleration on a mass of 1 kilogram equal to 1 meter per second with no friction and under the conditions of a vacuum.

Niche
Adaptive role that a species has in a habitat. This includes its behavior and interactions with other species.

Niche Specialization
Process where evolution, through natural selection, adapts a species to a particular set of abiotic and biotic characteristics within a habitat.

Nickpoint (Knickpoint - British spelling)
Point on the long profile of a stream where the gradient is broken sudden drop in elevation. Nickpoints are the locations of rapids and waterfalls.

Nimbostratus Clouds
Dark, gray low altitude cloud that produces continuous precipitation in the form of rain or snow. Found in an altitude range from the surface to 3,000 meters.

Nitrate
Form of nitrogen commonly found in the soil and used by plants for building amino acids, DNA and proteins. It is commonly produced by the chemical modification of nitrite by specialized bacteria. Chemical formula for nitrate is NO3-.

Nitric Acid
Acid with the chemical formula: HNO3.

Nitric Oxide
A gas produced by bacterial action in the soil and by high temperature combustion. Nitric oxide is a component in the production of photochemical smog. This colorless gas has the chemical formula is NO.

Nitrification
The biochemical oxidation of ammonium to nitrite and nitrite to nitrate. This process is carried out by specialized bacteria.

Nitrite
Form of nitrogen commonly found in the soil. It is commonly produced by the chemical modification of ammonium by specialized bacteria. This form is toxic to plants and animals at high concentrations. Chemical formula for nitrite is NO2-.

Nitrogen Cycle
Model that describes the movement of nitrogen in its many forms between the hydrosphere, lithosphere, atmosphere and biosphere.

Nitrogen Dioxide
A gas produced by bacterial action in the soil and by high temperature combustion. Nitrogen dioxide is a component in the production of photochemical smog. This reddish brown gas has the chemical formula NO2.

Nitrogen Fixation
Biological or chemical process where gaseous nitrogen is converted into solid forms of nitrogen. Biological fixation of nitrogen is done by specialized organisms like microorganisms like bacteria, actinomycetes, and cyanobacteria. Chemical fixation occurs at high temperatures. One natural process that can produce enough heat to fix atmospheric nitrogen is lightning.

Nitrogen Oxides
Consists of two gases nitric oxide (NO) and nitrogen dioxide (NO2). These gases are produced by bacterial action in the soil and by the high temperature combustion. Both gases are components in the production of photochemical smog.

Nitrogen Saturation
Over abundance of nitrogen in natural ecosystems because of human induced inputs related to agriculture and fossil fuel combustion.

Nitrous Oxide
Gas found in the atmosphere that contributes to the greenhouse effect. Sources for nitrous oxide include: land-use conversion; fossil fuel combustion; biomass burning; and soil fertilization. Chemical formula for nitrous oxide is N2O.

Nivation
Process where snow patches initiate erosion through physical weathering, meltwater flow, and gelifluction.

Nivation Hollow
Ground depression found in periglacial areas that is created by nivation.

Noctilucent Clouds
High altitude clouds composed of ice crystals that appear to glow silver or bright blue shortly after sunset.

Non-Clastic Sedimentary Rock
Sedimentary rocks that are created either from chemical precipitation and crystallization, or by the lithification once living organic matter.

A form of electromagnetic radiation that does not have enough energy to cause ionization of atoms in living tissue. Examples of this type of radiation include radio waves, microwaves, infrared light, and ordinary light. Also see ionizing radiation.

Non-Parametric Statistical Test
Statistical tests that do not assume the sample data is normally distributed.

Non-Renewable Resource
Resource that is finite in quantity and is being used faster than its ability to regenerate itself.

Nonsymbiotic Mutualism
Mutualistic interaction where the mutualists live independent lives yet cannot survive without each other. For example, pollinating insects like bees and some flowering plants.

Normal Distribution
A common probability distribution displayed by population data. If the values of the distribution are plotted on a graph's horizontal axis and their frequency on the vertical axis the pattern displayed is symmetric and bell-shaped. The central value or mean represents the peak or the most frequently occurring value.

Normal Fault
Vertical fault where one slab of the rock is displaced up and the other slab down. It is created by tensional forces acting in opposite directions.

Normal Lapse Rate
Average rate of air temperature change with altitude in the troposphere. This value is approximately a decrease of 6.5° Celsius per 1000 meters rise in elevation.

Northing
Second measurement of a grid reference used to specific the location of a point on a rectangular coordinate system. The distance measured northward from the origin of a rectangular coordinate system.

North Magnetic Pole
Location in the Northern Hemisphere where the lines of force from Earth's magnetic field are vertical. This point on the Earth gradual changes its position with time.

North Pole
Surface location defined by the intersection of the polar axis with Earth's surface in the Northern Hemisphere. This location has a latitude of 90° North.

Nuclear Energy
Energy released when the nucleus of an atom experiences a nuclear reaction like the spontaneous emission of radioactivity, nuclear fission, or nuclear fusion.

Nucleic Acid
Is an organic compound composed primarily of different combinations of carbon, hydrogen, nitrogen, oxygen, and phosphorus. They are very complex compounds being created by the atomic linking of thousands of individual atoms. DNA or deoxyribonucleic acid, the genetic blueprint of life, is an example of a nucleic acid.

Nucleus
(1) Dense central portion of an atom that is composed of neutrons and protons.
(2) Structure found in eukaryotic cells that contains the chromosomes.

Nuee Ardente
A glowing cloud of dense hot volcanic gas and ash that moves downslope at high speeds, incinerating the landscape.

Null Hypothesis (H0)
Is a hypothesis that has been suggested because it is believed to be true or because it is to be used as a starting point for scientific argument. Used in statistical testing to organize arguments.

Nutrient
Any food, chemical element or compound an organism requires to live, grow, or reproduce.

Nutrient Cycle
The cycling of a single element by various abiotic and biotic processes through the various stores found in the biosphere, lithosphere, hydrosphere, and atmosphere.

Citation: Pidwirny, M. (2006). "Glossary of Terms: N". Fundamentals of Physical Geography, 2nd Edition. Date Viewed. http://www.physicalgeography.net/physgeoglos/n.html

 Created by Dr. Michael Pidwirny & Scott Jones University of British Columbia Okanagan Email Corrections and Suggestions to: Copyright © 1999-2008 Michael Pidwirny 05/07/2009 15:28

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