Geoscience Reference
In-Depth Information
Ombrotrophic -
Peatland that receives all of its
nutrients exclusively from rain (including
snow and atmospheric fallout), which makes
nutrients extremely oligotrophic. Also named
ombrogenous.
Oxbow -
Abandoned river channel, usually
curved or loop shaped, that may contain a
lake, swamp or marsh.
Pakihi -
Peatland in southwestern New Zealand
dominated by sedges, rushes, ferns, and scat-
tered shrubs. Usually found on terraces or
plains of glacial or l uvial outwash; acidic and
exceedingly infertile.
Paleosol -
Ancient, fossil or buried soil that
formed under past climatic and biologic con-
ditions that may be quite different from the
modern environment.
Palsa -
Peatland found near the southern limit
of tundra region, consisting of large peat pla-
teaus that are 20 to 100 m in width and length
and up to 3 m high, generally underlain by
permafrost. Also spelled paalsa. Etymol: Sami.
Paludii cation -
Creation of wetlands by rising
ground water which leads to saturation of the
soil and ponding at the surface.
Palustrine -
Non-tidal wetlands that are sub-
stantially covered with emergent vegetation
including bogs, swamps, l oodplains and
marshes.
Palynology -
Scientii c study of pollen, its clas-
sii cation and environmental signii cance.
Panne (pan) -
Bare, muddy spots within salt-
marsh complex, normally above tidal range,
but may be l ooded occasionally.
Pangaea -
Ancient supercontinent that included
all modern continents during the late Paleo-
zoic and early Mesozoic.
Pântano -
Swamp or bog in South America.
Etymol: Portuguese.
Páramo -
Term specii c to the Andes Mountains
of Venezuela and Columbia referring to the
wet alpine zone characterized by perennial
cloud cover in which annual precipitation
exceeds 2.5 m.
Pearl -
Organic concretion formed within
certain mollusks and often valued as
gemstones.
Peat -
Organic-rich soil characterized by anaer-
obic and acidic conditions and consisting pri-
marily of partly decayed plant materials that
are still recognizable. Varieties are i bric,
hemic, and sapric, which are respectively
least, partly, and most decomposed.
Peatland -
All types of wetlands, including
bogs, fens and swamps, in which peat has
built up and continues to accumulate from
partly decayed plant materials. Equivalent to
mire.
Permafrost -
Soil and ground that remains per-
manently frozen at depth; a shallow active
layer may thaw during the summer. Typical
of high-latitude regions.
Phreatophyte -
Vegetation with deep roots that
reach the water table; typical in semi-arid and
arid riparian environments.
Plant hardiness zone -
Geographic range
of climatic conditions, primarily minimum
winter temperature, that limit plant survival.
Playa
(coast)
-
a) Small, generally sandy, land
area at the mouth of a stream or along the
shore of a bay. b) Flat, alluvial coastland, as
distinguished from a beach. Etymol: Spanish
- beach, shore, strand or coast.
Playa
(geomorph)
-
Dry, vegetation-free l at
area at the lowest part of an undrained
depression underlain by stratii ed clay, silt or
sand and commonly by soluble salts. May be
marked by an ephemeral lake. See also salina,
salar, salada. Syn: dry lake, vloer, sabkha,
kavir, takir. Playa basin
bolson.
Pleistocene -
Next to last epoch of the geologic
time scale,
=
2.6 million to 10,000 years ago.
Popularly associated with the Ice Age, during
which ice sheets, sea level, and climate
underwent multiple cycles of glaciation and
interglaciation.
Pneumatophore -
Plant breathing roots that
grow from saturated soil up into the air to
allow for gas exchange.
Pocosin -
Peat-accumulating, non-riparian,
fresh-water wetland, generally dominated by
evergreen shrubs and trees. Coastal plain of
southeastern U.S. Etymol: Algonquin - swamp
on a hill.
Pothole -
Shallow, marshlike pond, particularly
in the U.S. Dakotas and Canadian Prairie
provinces; prairie pothole region.
Prop (stilt) roots -
Root system that holds plant
body above the ground or water surface, as
in many mangroves.
∼
