Bioturbation of soil and subsoil is the physical

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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 playa. 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 leaves. 9 C 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 ground-water reservoir. 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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