Geo Soils Exam #2

Chp 6 - Ch 11 UWF Dr Gilliam

ocean

holds 97% of earth’s water

permafrost/snow

holds 2% of earth’s water

groundwater

holds 1% of earth’s water

atmosphere

holds 0.001% of earth’s water

global hydrological cycle

interplay of water as it moves through the largest global stock (ocean) and smallest global stock (atmosphere)

evaporation

transformation or loss of H2O from a liquid to a gas/vapor

transpiration

loss of H2O vapor from leaves through stomates

evapotranspiration

total return of H2O to the atmosphere from the earth’s surface, including evaporative loss from the surface and transpiration loss from plants

global H2O vapor

2.6 cm total

global ppt

66 cm/year

global turnover

26 times per year, ppt/H2O vapor

throughfall

gross precipitation that passes through the plant canopy to the surface

stemflow

precipitation intercepted by stems, branches, and trunks, later draining through them

interception

total precipitation trapped by leaves, stems, and leaf litter

precipitation

liquid vapor entering a system from clouds

gravitational water

amount of water following saturation that moves out of a soil column from the pull of gravity

water table

underground zone of an aquifer where the saturated zone and unsaturated zone meet

water balance equation

precipitation = soil storage + evapotranspiration + discharge

P = SS + ET + D

discharge (D)

water moving out of a drainage system on the surface and below the surface as runoff

soil storage

capacity of soil water held by pores through capillary and matric processes

↓ Ts =

↑ H2O yield

watershed

any area of land drained by a single stream

watershed divide

elevated boundary line that separates drainage basins

percolation

gravitational movement of water through soil pores and permeable rock

tributaries

smaller stream which flows into a larger main river

aquifer

underground layer of semipermeable rock holding groundwater in varying degrees

plant canopy

upper layer of plant branches and leaves which catch precipitation

prairie pothole

shallow, depressional freshwater wetland formed by glacial activity

↑ canopy height/size =

↑ intercepted precipitation

interception =

ppt - (TF + SF)

infiltration

process of surface water entering the soil profile

↑ vegetation =

↑ soil infiltration

↑ soil management =

↑ infiltration

↑ tillage =

↓ infiltration

↑ urban watershed =

↓ infiltration

↑ runoff

fragipan

dense, prismatic, cemented layer of soil causing a bottleneck for infiltrating water

open stable soil structure =

↑↑↑ infiltration

soil plant atmosphere continuum (SPAC)

continuous and integrated system of water traveling through the pedosphere, biosphere, and atmosphere through precipitation and evapotranspiration; driven by different water potentials

water potentials

potential energy gradient of soil water relative to pure H2O

Pure H2O Ψ =

0 MPa

saturation water

amount of water under saturated conditions (0 MPa)

field capacity

amount of water in the soil after movement of gravitational water (-0.015 MPa)

permanent wilting point (PWP)

amount of water in soil following enough drying to lead to permanent wilting of leaves (-1.5 MPA)

available soil water =

field capacity - PWP

hygroscopic coefficient

maximum amount of water a dry soil can absorb from a saturated atmosphere; completely unavailable from plants (-3.10 MPa)

soil water

water in the pores of a soil profile

soil moisture

total level of soil water held in the pores of a soil profile

water use efficiency

capacity of a plant to use water before transpiration dependent on soil texture, structure, OM, and climate

ET efficiency

how effectively soil and plants hold usable water

hydraulic redistribution

passive movement of soil water from moist to dry soil across the water potential gradient

xylem

vascular plant tissue that transports water up the stem with cohesion and adhesion

stoma

microscopic pore on plant leaf that releases water through transpiration

cohesion

attraction between identical molecules

adhesion

attraction between different molecules

water deficit

water demand of evapotranspiration > precipitation and soil moisture

leaching

loss of minerals, nutrients, and organic matter through the dissolving of downward moving water

runoff

excess surface water not absorbed by soil

atmospheric Ψ

-100 MPa

leaf at top of tree Ψ

-1.5 MPa

stem Ψ

-0.6 MPa

root cells Ψ

-0.2 MPa