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Unformatted text preview: of soil and subsoil is the physical rearrangement of sediment particles forming the
soil and subsoil fabric by churning, stirring, or disruption through organic or biophysical
processes of resident lifeforms; included types of bioturbation, or faunal and floral soil
disturbance, are the effects of worms, rodents, and ungulates, as well as root expansion and, in
forested areas, sediment movement due to treefall.
Block field is a continuous surface cover of large angular to subangular rocks derived from a
source of well jointed bedrock either beneath or upslope from the block covering. The blocks
are generally dislodged by frost action and form a layer greater than one or two clast
thicknesses (as opposed to a rock veneer, which has a thickness no greater than two clast
thicknesses). A block field can occur on a steep slope if the source rock is exposed along a high
ridge or similar topographic feature, whereas the term felsenmeer refers to a block field that
occurs on a flat or gently sloping surface that is derived from an underlying source
Bole, derived from an English term for a shade of brown, refers to the trunk, or stem, of a tree;
as applied by plant ecologists, the bole of a tree is often the wood of the trunk and does not
necessarily include the bark.
Bolson, or playa basin, is a drainage basin of an arid to semiarid area with interior drainage
toward the playa; it is the surface area that contributes excess precipitation, as runoff, to the
Bottomland is that part of an alluvial valley formed of and underlain by alluvium that has been
transported by and deposited by the stream flowing through the valley reach; bottomlands may
include the channel bed and one or more terraces.
Boulder, as bed sediment or bed material, is sediment defined to be of particle diameter
greater than 256 mm in diameter (b-axis).
Brackish water is water on or beneath a land (or water) surface that accumulates as a result of
natural processes of precipitation and which contains dissolved solids (mostly salts) of
concentration intermediate between that of fresh water and salt water; the concentration of
dissolved solids in brackish water is sufficient to cause deleterious effects by ingestion of living
organisms adapted to a dependency on fresh water.
Braided stream is one with a wide, relatively horizontal channel bed over which water during
low flows forms an interlacing pattern of splitting into numerous small conveyances that again
coalesce a short distance downstream; the conveyances, or sub-channels, lack channel
characteristics, are highly ephemeral, and thereby are distinguishable from anabranches. A
synonym is anastomosing stream, a biological term referring to the vein patterns of some plant
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Caespitose trees are those with trunks growing in clusters or tufts. As applied to plant ecology
and hydrology, caespitose trees are generally willows and cottonwoods that have been sheared
at the surface by a destructive flood; if the root system survives the event, multiple trunks are
likely to spout from the below-surface root mass.
Calcrete, a calcium-rich type of duricrust, is a near-surface pedogenic accumulation, usually less
than a meter in thinckness, of secondary precipitates of calcium carbonate and other calcium or
silica salts. Calcrete is typical of a semiarid climate and forms a poorly permeable to nearly
impermeable layer or crust binding silt, sand, and gravel of poorly developed mineral soils.
Because calcrete formation reduces soil permeability and porosity, infiltrating rainfall may be
temporarily perched on its top, providing soil moisture to vegetation.
Canopy is the cover or crown of leaves, needles, and branches of trees forming a forest; the
canopy affects erosion by intercepting rainfall and causing evaporation of a portion of it,
thereby preventing that portion from reaching the surface and becoming runoff, and by
protecting soil particles at the surface from erosion by rainsplash impact.
Capillary fringe is a zone of the subsurface that is continuous with the overlying zone of
saturation, contains capillary interstices (some or all of which are filled with water), and in
which the pressure is less than atmospheric.
Carrying capacity of a watershed, landscape, drainage network, lake, or ground-water system is
the production, through natural biophysical processes, of ecosystem services that each can
yield without sustaining loss in function; for a grassland the carrying capacity might be the
annual growth of grass that can support grazing by herbivores without environmental damage,
whereas the carrying capacity of a ground-water system is the rate at which water can be
extracted from wells, and replaced by natural recharge, without a reduction in volume of the
Capacity of a stream, which is synonymous with competence, or stream competence, refers to
the ability of a current of water (or wind) to transport specified particle sizes of sediment.
Catchment is a synonym for drainage basin, but the term often has the connotation of a
smaller area than that of a drainage basin (a sub-basin).
Catena, from th...
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This document was uploaded on 02/26/2014 for the course ES 322 at Western Oregon University.
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