Gallery forest
Narrow bands of forest along stream drainages.

Gene
A specific sequence of DNA that encodes for a specific trait, characteristic, or protein in an organism.

General circulation models (GCMs)
Mathematical representations of atmospheric and oceanic properties and processes that attempt to describe earth's climate system.

Genotypes
Individuals within a species that differ slightly in their genetic composition.

Geodetic
Something pertaining to or determined by the physical shape of the earth or a large portion of its surface.

Graminoids
Species of plants that typically are considered to be grasses or grass-like in morphology and function.

Greenhouse effect
A global warming phenomenon that results from the increase in the atmospheric concentration of a gas that is relatively transparent to the short wavelength solar radiation that emanates from the sun but that is fairly opaque to the longer wavelength thermal radiation that emanates from the surface of a planet.

Growth respiration
Respiration in which energy is used for the construction of new biomass.

Global carbon cycle
The cyclical movement of carbon within the biosphere.  Carbon is primarily removed from the air by plants during photosynthesis and by dissolving in bodies of water.  Carbon is generally returned to the air via biological respiration, decomposition of organic matter, volcanic activity, and society's industrial activities, including the combustion of fossil fuels.

Greenhouse gases
Gases such as water vapor, carbon dioxide and methane that are relatively transparent to the short wavelength solar radiation that emanates from the sun but that are fairly opaque to the longer wavelength thermal radiation that emanates from the surface of a planet.

Grounding line
The location where glacial ice resting on solid earth gives way to floating ice.

Guard cells
The specialized epidermal cells that regulate the aperture of stomata.