Principles of terrestrial ecosystem ecology.pdf

Exoenzyme. Enzyme that is secreted by an
organism into the environment.
Extensification. Expansion of the aerial
extent of land cover change due to human
activities.
Extinction coefficient. Constant that describes
the exponential decrease in irradiance
through a canopy.
Exudation. Secretion of soluble organic compounds
by roots into the soil.
Facilitation. Processes by which some species
make the environment more favorable for
the growth of other species.
Fast variable. Variable that changes rapidly.
Feedback. Response in which the product of
one of the final steps in a chain of events
affects one of the first steps in this chain;
fluctuations in rate or concentration are minimized
with negative feedbacks or amplified
with positive feedbacks.
Fermentation. Anaerobic process that breaks
down labile organic matter to produce
organic acids and CO2.
Ferrell cell. Atmospheric circulation cell
between 30° and 60° N or S latitude.
Field capacity. Water held by a soil after
gravitational water has drained.
Filter feeder. Aquatic animal that feeds on
suspended particles.
Fine particulate organic matter. Particulate
organic matter in aquatic ecosystems that is
smaller than 1mm diameter.
Fire intensity. Rate of heat production.
Fixation. Covalent binding of an ion to a
mineral surface.
Flux. Flow of energy or materials from one
pool to another.
Food chain. Group of organisms that are
linked together by the linear transfer of
energy and nutrients from one organism to
another.
Food web. Group of organisms that are
linked together by the transfer of energy and
nutrients that originates from the same
source.
Forward modeling. Modeling that estimates
the outputs of a simulation model based
on the temporal and spatial patterns of
inputs.
Glossary 381
Fractionation. Preferential incorporation of a
light isotope (e.g., 12 C vs. 13 C).
Fragmentation. Breaking up of intact litter
into small pieces.
Fulvic acids. Humic compounds that are
relatively water soluble due to their extensive
side chains and many charged
groups.
Functional type. A group of species that is
similar with respect to their impacts on
community or ecosystem processes (effects
functional type); functional types have also
been defined with respect to their similarity
of response to a given environmental change,
such as elevated CO2 (response functional
types).
Gap-phase succession. Succession that occurs
in small patches within a stand due to death
of individual plants or plant parts.
Gelisol. Soil order characterized by presence
of permafrost.
Generalist herbivore. Herbivore that is relatively
nonselective in its choice of plant
species.
Geotropism. Growth response of plant organs
with respect to gravity.
Gley soil. Blue-gray soil due to loss of
ferric iron; formed under anaerobic
conditions.
Graminoid. Grasslike plant (grasses, sedges,
and rushes).
Grazer. Herbivore that consumes herbaceous
plants (terrestrial ecosystems) or periphyton
(aquatic ecosystems).
Grazing lawn. Productive grassland or wetland
ecosystem in which plants are heavily grazed
but supported by large nutrient inputs from
grazers.
Greenhouse effect. Warming of the atmosphere
due to atmospheric absorption of
infrared radiation.
Greenhouse gas. Atmospheric gas that absorbs
infrared radiation.
Gross primary production. Net carbon
input to ecosystems—that is, net photosynthesis
expressed at the ecosystem scale
(gCm -2 yr -1 ).
Ground heat flux. Heat transferred from the
surface into the soil.