Principles of terrestrial ecosystem ecology.pdf

Phototroph. Nitrogen-fixing microorganism
that produces its own organic carbon through
photosynthesis.
Phreatophyte. Deep-rooted plant that taps
groundwater.
Phyllosphere decomposition. Decomposition
that occurs on leaves before leaf fall.
Phytoplankton. Microscopic algae suspended
in the surface water of aquatic ecosystems.
Pixel. Individual cell of a satellite image that
provides a generalized spectral response for
that area.
Planetary boundary layer. The layer of the
atmosphere that is directly affected by the
fluxes and friction of Earth’s surface.
Planetary wave. Large (greater than 1500km
length) wave in the atmosphere.
Plankton. Microscopic organisms suspended
in the surface water of aquatic ecosystems.
Plant-based trophic system. Plants, herbivores,
and organisms that consume herbivores and
their predators.
Plant defense. Chemical or physical property
of plants that deters herbivores.
Plasmodesmata. Cytoplasmic connections between
adjacent cortical cells.
Plinthite layers. Laterite layers in tropical soils.
Podzol. Spodosol.
Poikilothermic. Organism whose body temperature
depends on the environment.
Polar cell. Atmospheric circulation cell
between 60° and the pole driven by
subsidence at the poles.
Polar front. Boundary between the polar and
subtropical air masses characterized by rising
air and frequent storms.
Polyphenol. Soluble organic compound with
multiple phenolic groups.
Pool. Quantity of energy or material in an
ecosystem compartment such as plants or
soil.
Positive feedback. Interaction in which two
components of a system have a positive effect
on the other or in which both have a negative
effect on one another; this amplifies the
rate of change in the system.
Potential biota. Organisms that are present in a
region and could potentially occupy the site.
Potential vegetation. Vegetation that would
occur in the absence of human disturbance.
Glossary 387
Precession. A “wobbling” in Earth’s axis of
rotation with respect to the stars, determining
the date during the year when solstices
and equinoxes occur.
Precipitation. Water input to an ecosystem as
rain and snow.
Pressure potential. Component of water
potential generated by gravitational forces
and by physiological processes of organisms.
Prevailing wind. Most frequent wind direction.
Primary forest. Forest that has never been
cleared.
Primary minerals. Minerals present in the rock
or unconsolidated parent material before
chemical changes have taken place.
Primary producers. Organisms that convert
CO2, water, and solar energy into biomass
(i.e., plants); synonymous with autotroph.
Primary production. Conversion of CO2,
water, and solar energy into biomass. Gross
primary production is the net carbon input
to ecosystems, or the net photosynthesis expressed
at the ecosystem scale (gCm -2 yr -1 ).
Net primary production is the net carbon
accumulation by vegetation (GPP minus
plant respiration).
Primary succession. Succession following
severe disturbances that remove or bury most
products of ecosystem processes, leaving little
or no organic matter or organisms.
Production efficiency. Proportion of assimilated
energy that is converted to animal
production, including both growth and
reproduction.
Profile. Vertical cross-section of soil.
Protease. Protein-hydrolyzing enzyme.
Proteoid roots. Dense clusters of fine roots
produced by certain families such as the
Proteaceae.
Protozoan. Single-celled animal.
Quality. Chemical nature of live or dead
organic matter that determines the ease with
which it is broken down by herbivores or
decomposers, respectively.
Quantum yield. Moles of CO2 fixed per mole
of light quanta absorbed; the initial slope of
the light-response curve.
Quinone. Highly reactive class of compounds
produced from polyphenols.