Principles of terrestrial ecosystem ecology.pdf

390 Glossary
Soil phase. Soils belonging to the same soil
type that differ in landscape position, stoniness,
or other soil properties.
Soil resources. Water and nutrients available in
the soil.
Soil series. Soils belonging to the same order
that differ in profile characteristics, such as
number and types of horizons, thickness, and
horizon properties.
Soil structure. Binding together of soil particles
to form aggregates.
Soil types. Soils belonging to the same soil
series but having different textures of the A
horizon.
Solifluction. Downslope flow of saturated soils
above a frozen layer.
Solubility pump. Downward flux of carbon
from surface to deep waters due to the
downwelling of CO2-rich North Atlantic or
Antarctic waters.
Sorption. Binding of an ion to a mineral
surface, ranging from electrostatic attraction
to covalent binding.
Source. Part of a plant that shows a net export
of a compound.
Southern oscillation. Atmospheric pressure
changes over the southeastern Pacific and
Indian Ocean.
Specialist herbivore. Herbivore that specializes
on consumption of one or a few plant
species or tissues.
Species composition. Identity of species in an
ecosystem.
Species diversity. Number, evenness, and composition
of species in an ecosystem; the total
range of biological attributes of all species
present in an ecosystem.
Species evenness. Relative abundances of
species in an ecosystem.
Species richness. Number of species in an
ecosystem.
Specific heat. Energy required to warm a gram
of a substance by 1°C.
Specific leaf area. Ratio of leaf area to leaf
mass.
Specific root length. Root length per unit root
mass.
Spiraling length. Average horizontal distance
that a nutrient moves between successive
uptake events.
Spodosol. Soil order characterized by highly
leached soils that develop in cold climates;
Formerly termed podzols.
Stand-replacing disturbance. Large disturbances
that affect entire stands of vegetation.
State factors. Independent variables that
control the characteristics of soils and ecosystems
(climate, parent material, topography,
potential biota, and time).
Steady state. State of a system in which increments
are approximately equal to losses,
when averaged over a long time (e.g., the
turnover time of the system); there are no
directional changes in the major pools in a
system at steady state.
Stem flow. Water that flows down stems to the
ground.
Stomata. Pores in the leaf surface through
which water and CO2 are exchanged between
the leaf and the atmosphere.
Stomatal conductance. Flux of water vapor or
CO2 per unit driving force between the leaf
and the atmosphere.
Stratopause. Boundary between the stratosphere
and the mesosphere.
Stratosphere. Atmospheric layer above the
troposphere, which is characterized by an
increase in temperature with height.
Strength of soil. Amount of force required to
initiate slope failure.
Stress. Environmental factor that reduces
plant performance; physical force that promotes
mass wasting of soils.
Stroma. Gel matrix within the chloroplast in
which the carbon-fixation reactions occur.
Subduction. Downward movement of a plate
margin beneath another plate.
Suberin. Hydrophobic waxy substance that
occurs in the cell walls of the endodermis and
exodermis of plant roots.
Sublimation. Vaporization of a solid.
Subsidy. Energy or nutrient transfers from one
ecosystem to another; synonymous with
allochthonous input.
Succession. Directional change in ecosystem
structure and functioning resulting from
biotically driven changes in resource supply.
Sunfleck. Short period of high irradiance that
interrupts a general background of low
diffuse radiation.