- S alleles
- Alleles that control the self-incompatibility response.
- scavenger
- An opportunist who searches for or takes advantage of useful dead organic material
- scree
- Accumulation of unsorted rock fragments of fist-size or smaller. Result of in-place weathering of larger rock fragments e.g. on a talus slope
- sedimentary rock
- Rock formed by the deposition and compression of mineral and rock particles, often also including material of organic origin. It may be classified as a terrigenous, organic or chemical sediment.
- segregation ice
- Ice in discrete layers or ice lenses, formed by ice segregation
- self-incompatibility
- The inability of a fertile hermaphrodite seed plant to produce zygotes after self-pollination. A mechanism ensuring outbreeding.
- selfing
- Fertilisation of an ovule by a pollen grain of the same genetic individual.
- senescence
- Decline of physiological state with age causing a decrease in fecundity and an increase in mortality.
- sesquioxides
- General term for the hydrated oxides and hydroxides of iron and aluminum
- small intestine
- The small intestine, despite its name, is the longest part of the digestive tract. Food that passes from the stomach into the small intestine, is broken down there into nutrients that the body can absorb and use. Most of the digestive process occurs in the small intestine.
- snow line
- The lower limit of permanent snow cover, below which snow does not accumulate
- solifluction
- Gradual downhill movement of saturated soil upon an impermeable layer of frozen ground or bedrock; produces terraces and lobes
- species diversity
- The variety of species within a particular geographical area
- sporadic discontinuous permafrost
- (a) (North-American usage) Permafrost underlying 10 to 35 percent of the exposed land surface
(b) (Russian usage) Permafrost underlying 5 to 30 percent of the exposed land surface
- stigma
- Part of the gynoecium which receives pollen grains on papillae, often borne on the end of a style.
- stomata
- Pores in the leaf which actively regulate gas exchange
- strategy
- A behavior or set of behaviors used by an individual to deal with an important lifehistory problem. Strategies are largely innate, but can also be learned.
- subalpine
- A term with many different definitions referring either to the transition between the upper montane forest to the alpine belt (a synonym to treeline ecotone) or the varying parts of the upper montane forest itself
- subarctic
- climate: characterized by very cold winters, and brief, often warm, summers. This kind of climate offers some of the most extreme seasonal temperature variations found on the planet: In winter, temperature can drop to -40° Celsius and at summer, the temperature may reach 30° Celsius. Most subarctic reagions are also affected by inland climate.
- subglacial
- The area below the glacier. Subglacial features include deformed sediments, ice caves, and eskers, mounds of sand, gravel or boulders.
- subnival
- The transition zone from the alpine to the nival belt
- succession
- The process of sequential change in species composition. Primary succession denotes vegetation development on newly exposed substrate without prior soil development. In a secondary succession, at least some pre-disturbance soil remains.
- symbiont
- One of the partners in a symbiosis
- symbiosis
- (s. l.) A close, often obligatory association of organisms of different species
(s. str.) A close, often obligatory association of organisms of different species with an advantage for all partners
- sympatric
- Occurring in the same area without interbreeding
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