Knob – This rarely used term refers to a glacial deposit
in the shape
of an isolated hill. This hill is treeless (hence, it is 'bald') and
surrounded by relatively flat land. In the absence of development, a
bald knob supports prairie vegetation. With greater elevation, a bald
knob can support rocky alpine vegetation, although this type of habitat
is not found in Illinois.
– This ecological term is somewhat ambiguous in its meaning. As
it is used here, a "barrens" refers to a relatively open upland area
that is very rocky or sandy (similar to a glade, but less
prairie-like). A barrens is capable of supporting a few stunted trees,
small shrubs, and some ground vegetation. In the past, a
"barrens" often referred to any open area that had been burned-over,
regardless of the characteristics of the soil. It was assumed that such
burned-over areas had sterile soil, which was often not the case.
– A low sandy area along a major lake or river. The lower area of
a beach that is adjacent to a body of water supports very little
vegetation as a result of frequent wave action, however the upper area
of a beach can support small shrubs and various kinds of ground
vegetation that are adapted to very sandy areas.
– This is a wooded hill. Bluffs often occur along major rivers.
They tend to have smaller and less densely distributed trees than
woodlands on lower ground. As a result, they often support more shrubs
and ground vegetation.
– This is a wetland that is supplied with water solely
rainfall, rather than through a river, spring, or seep. The soil of a bog tends to be dominated by sphagnum moss or peat and it
is highly acidic. Because of the acidic water and low level of
nutrients in the soil, bogs support a more restricted variety of
vegetation. Open bogs support primarily ground vegetation consisting of
grasses, sedges, forbs (flowering dicots), and low shrubs, while
forested bogs support such trees as Tamarack (Larix decidua) and Black
Spruce (Picea mariana). A forested bog that is dominated by Tamarack is
referred to as a 'Tamarack Bog.' Bogs occur primarily in more northern
areas where the climate is cool and moist.
– This is an unusually large ravine that has a relatively large
flat bottom with steep rocky slopes on either side. The bottom of the
canyon consists of a river and the surrounding flood zone
area. Canyons often contain some trees, but they are stunted in size
and more sparsely distributed than surrounding wooded
areas. This is a rare ecological system in Illinois.
– A steep rocky slope, often facing a river valley or a canyon.
In Illinois, cliffs are usually found in the southern part of the
state, where they may consist of either limestone or sandstone. Some
kinds of vegetation are often found at the top of cliffs, while other
kinds of vegetation are found at the bottom of cliffs. Some small ferns
have specialized in colonizing the crevices of cliffs; they often
display a preference for cliffs consisting of either sandstone
(acidic substrate) or limestone (alkaline substrate).
– This is a relatively open
wetland that is supplied with water from an underwater spring or seep.
The mineralized ground water of a fen can support a variety of ground
vegetation, including some shrubs and small trees. Where Northern White
Cedar (Thuja occidentalis) is abundant in this kind of wetland habitat,
it is referred to as a 'White Cedar Fen.' The pH of the soil in a fen
varies from mildly acidic to alkaline.
– A flatwoods occurs on a depression in an upland wooded area where
the underlying soil contains a layer of clay, causing poor drainage. A
flatwoods contains trees that tolerate considerable variation in
moisture levels, from flooded conditions during the spring to droughty
conditions during late summer.
– This is a meadow
that occurs on thin rocky soil in a hilly wooded area. Glades are
normally located on top of a hill or mountain where a plateau exists.
They are usually surrounded along their margins by trees and other
woody vegetation (typically woodlands or savannas). The rocky soil is
usually too thin to support trees, although some glades are maintained
by occasional fires. The underlying bedrock of a glade can consist of
limestone, sandstone, chert (quartz-laden rock), and other rocky
material. Glades are found primarily in southern Illinois.
Bar – This is a low deposit of gravel along a
river. Gravel bars are sometimes created as a result of repeated flooding along major rivers.. They
primarily herbaceous ground vegetation that can colonize moist gravelly
that are subjected to occasional disturbance.
– A ledge usually refers to a short rocky shelf along a steep
vertical cliff. A ledge may be located at the top of a cliff, or it may
be located at a lower level of the cliff. Cliffs develop ledges in
response to past water erosion from flooded rivers. As a river sinks
lower into the bedrock, it can create new ledges during floods.
Different kinds of ground vegetation can be found along ledges,
depending on whether it is an exposed ledge (facing the wind and
sunlight), or a sheltered ledge (protected from wind and sunlight).
– This is a
wetland with a small body of open water that is surrounded primarily by
emergent aquatic vegetation and some ground vegetation, especially
sedges, bulrushes, and cattails. Some wetland shrubs (e.g., willows)
may colonize drier ground along the edge of a marsh. A marsh
may be adjacent to a lake or slow-moving river, or it may be isolated
from other wetlands. The ground soil of a marsh may be sandy or muddy
and, unlike the ground soil of a bog, it is not strongly acidic.
– As used here, a "meadow" refers to a sunny open area that
often surrounded by trees and other woody vegetation. The ground
vegetation of such meadows consists of grasses, sedges, and forbs
(flowering dicots). Some low shrubs and vines also occur in this
ecological system. Sometimes a meadow occurs along a river in an area
that is either too damp for most woody vegetation, or where beavers
destroy most of the woody vegetation. A special kind of flood-prone
meadow where sedges are dominant is called a "sedge meadow." Meadows
tend to occur where wooded areas
are the dominant ecological system, although some meadows are
surrounded by either water or development.
– This is a low flat sandy area that is prone to temporary
flooding by the water of a lake. Over time, a panne accumulates
minerals (including salt) that are suspended in the water as a result
of repeated evaporation. In Illinois, this habitat is found primarily
along Lake Michigan, where it is uncommon. Certain kinds of ground
vegetation and semi-aquatic vegetation can be found in sandy pannes
because of their need for minerals or their tolerance of saline
When this term is used in an ecological context, it refers to
a wooded area (usually somewhat open) that is mostly lacking in
shrubs, saplings, and
other low woody vegetation. A parkland can be the result of relatively
frequent ground fires that spare fire-resistant canopy trees, or it may
result from heavy grazing or mowing. The ground vegetation in a
parkland consists primarily of such herbaceous plants as grasses,
sedges, and forbs (flowering dicots).
Cemetery – Some cemeteries in Illinois were
established during pioneer days. Because of neglect, a small number of
these cemeteries and areas adjacent to these cemeteries have native
ground vegetation that has largely disappeared from more developed
areas of the state. Typically, such pioneer cemeteries and adjacent
areas are overgrown with prairie vegetation, although some of them also
have savanna and woodland vegetation along their edges.
Clearances – Electric power companies often
woody vegetation underneath powerlines. Such clearances create
temporary meadows where various kinds of ground vegetation and small
shrubs are dominant. When trees and other woody vegetation recolonize
such areas, they are cut to ground level yet again, enabling the
resurgence of ground vegetation. This cycle is repeatedly indefinitely.
Powerline clearances reduce or remove trees and other woody vegetation
from woodlands, overgrown fence rows, and other habitats. Telephone
companies engage in similar activities to a lesser extent.
– An open treeless
area consisting of grasses, sedges, and forbs (flowering dicots) as the
dominant ground vegetation. Some sub-shrubs and vines also occur in
this ecological system. Where prairies occur, they are usually the
dominant ecological system. As a result, prairies tend to surround
wooded areas, rather than the other way around. The moisture gradient
of prairies can vary from wet to dry. Different kinds of prairie have
been identified according to their soil type. In Illinois, this
includes black soil prairie, sand prairie, dolomite prairie, and gravel prairie. In the
past, prairies dominated the northern two-thirds of Illinois.
– This is a long deep depression that is surrounded on
both sides by steep slopes. Many ravines occur in rocky wooded areas
where the underlying bedrock has been exposed by water erosion. Either
temporary or permanent streamlets are often present at the bottom of
Bar – This is a low deposit of sand along a major river or
Sand bars are created as a result of repeated flooding or wave action. They support
primarily herbaceous ground vegetation that can colonize moist sandy
areas that are subjected to occasional disturbance.
Dune – This is a hill consisting primarily of sand that is
sometimes found along major rivers or lakes. Some inland sand dunes are
relatively isolated from major bodies of water because the rivers or
lakes that created them have disappeared from the vicinity a long time ago. Such
extinct rivers or lakes can be dated to an earlier time period, often
shortly after the last glaciation. Young sand dunes support
very little vegetation, but over time sand dunes become more
stabilized, when they can support some trees and other vegetation.
– This is a
thinly wooded area that admits some sunlight between the trees. The
trees in a savanna are more widely spaced apart than the trees of a
woodland. Because of the greater availability of sunlight, savannas
tend to support a greater variety of shrubs, vines, and ground
vegetation than a dense woodland. A savanna can occur as the result of
fire or other disturbance destroying some of the trees, or it may
result from a natural thinning of the trees because of the
characteristics of the soil (e.g., too sandy or rocky to
abundant trees). In Illinois, there are typical savannas with loamy
soil, sandy savannas, and rocky upland savannas. Oaks are often the
dominant trees in a savanna.
– This is a wetland that is caused by ground water slowly oozing to the
soil surface, creating an area that is more or less permanently damp
and soggy. A seep may occur on relatively low flat ground, or it may
occur along a hillside from the horizontal movement of ground water. At
some seeps, shallow pools of water may accumulate. Seeps can occur in
either open areas or wooded areas. In a wooded seep, the tree canopy
tends to be less dense than in drier areas.
– This is a river-like depression in a relatively open area that
becomes temporarily flooded after a heavy rain. Afterwards, the
slough dry up into puddles of water and exposed ground. The
water of a slough migrates (usually rapidly) to lower ground in another
– This is a wet pool-like depression in an open area that is
prone to temporary flooding. The water of a swale is stagnant and
doesn't migrate to other areas. When a swale occurs between adjacent
sand dunes it is called an "interdunal swale." Many swales are found in
This is a wetland that is dominated by flood-resistant trees. In
southern areas, Bald Cypress (Taxodium
distichum) and Water Tupelo
are common trees of swamps, while in more northern
areas swamps are dominated by various deciduous trees. Swamps usually
have standing water at certain times of year, although they are not
usually permanently flooded in most places. Drier areas of swamps support a variety of
understory and ground vegetation, while wetter areas support both
aquatic and emergent-aquatic plants.
– This is an area
that is dominated by shrubs and vines, rather than trees or low ground
vegetation. A thicket may occur at the edge of a wetland, woodland, or
prairie. Thickets may colonize burned-over woodlands or invade prairies
in the absence of fire. They also occur in wetlands that are too soggy
to support trees. When wetland areas are dominated by either willows
or alders (Alnus spp.),
they are referred to as 'Willow
Thickets' and 'Alder Thickets.'
Pool – This is a pool of water in a wooded area. A vernal
is usually filled with water after a period of rainy weather (especially during the
spring), but it has a tendency to dry out in response to a protracted
drought. Vernal pools often support shade-tolerant wetland vegetation
along their margins and they provide breeding grounds for certain amphibians (e.g., frogs and salamanders).
Ground – This refers to
open ground in a developed area that is largely ignored or poorly
maintained. It may refer to areas around junk yards, landfills, vacant
lots, neglected areas along back alleys, rail yards, grounds
surrounding abandoned buildings, and various edge habitats between
– This is an area
that is dominated by canopy trees. Underneath these canopy trees, there
is usually other kinds of vegetation consisting of shade-tolerant
understory trees, shrubs, woody vines, and herbaceous plants. However,
some canopy trees may cast shade that is sufficiently dense to kill
off understory and ground vegetation. Old-growth woodlands are
dominated by large old trees that eventually topple and fall to the
ground. Second-growth woodlands are dominated by younger trees that
have not achieved their full size. Woodlands can be dominated by either
deciduous trees or coniferous trees, although some woodlands are mixed
(consisting of both deciduous and coniferous trees). Floodplain
woodlands usually occur along the flood zone of rivers, although
sometimes they are on low ground that is far removed from
major bodies of water. Upland woodlands are more dry and
better-drained, although they may contain small moist depressions.
Border – This refers to the edge of a woodland along an
open area. This
open area may consist of a prairie or meadow, a clearance along a road
or some other developed area, or an open wetland.
Opening – This refers to a sunny
opening in a woodland that is too small to be considered a meadow.
Woodland openings are often caused by fallen trees.