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Topographic Effects
The Physical Environment
Organisms function within the set limits of physical laws.
Properties of Water• liquid at ambient temperature
• solid state less dense than liquid- max density @ 4o C
• specific heat- absorbs heat; stabilizing temperatures within geographic regions
• thermal conductivity• heat of vaporization• transparent- absorbs IR & UV• polar solvent
Statistics for Earth's Water
• water covers >70% of the earth's surface
Oceans 97.61% Polar Ice & Glaciers 2.08 Groundwater 0.29 Freshwater lakes 0.009 Saline Lakes 0.008 Soil Moisture 0.005 Rivers 0.00009 Atmosphere 0.0009
Hydrologic Cycle
Hydrologic Principles• The amount of water that soil holds,
and its availability to plants, varies with the physical properties of the soil.
• Capillary Action and Surface Tension
• Soil Water Potential and Field Capacity• As soil water decreases, the remainder is held
by increasingly stronger forces.
Temperature• life processes occur within the
range at which water is a liquid (0-100 o C)
• few plants and animals can survive body temperatures above 45 o C
• the freezing point of water may be lowered by dissolved substances
• tissues of most animals freeze at a higher temperature than that of sea water
Inorganic Nutrients
nitrogen phosphorus
sulfur potassium
calcium magnesium
iron
Major Nutrients and Functions
• Nitrogen (N): component of proteins
and nucleic acids
• Phosphorus (P): component of nucleic
acids, phospholipids, and bone
• Sulfur (S): component of many
proteins
• Calcium (Ca): bone; regulator of cell
permeability
Major Nutrients and Functions
• Magnesium (Mg): component of chlorophyll; involved in enzyme function
• Iron (Fe): component of hemoglobin and many enzymes
• Sodium (Na): major solute in extracellular fluid of animals
Hydrology and Drainage Basin Morphology
Water Balance EquationInputs-Outputs + Storage = 0
or
P=RO+ET+ Swhere:
P= precipitationRO= runoffET= evapotranspirationS= storage
Processes in the Hydrologic Cycle
precipitation (P)- liquid or solid state
evapotranspiration (ET)-
evaporation- conversion of solid or liquid water to gaseous water; can take place from open water, soil, or vegetative surfaces
transpiration- water taken up by plants is released in the gaseous phase
runoff (RO)-that part of precipitation that flows out of a watershed.
– 1. overland flow- flow occurs on impermeable surfaces or when the infiltration capacity of the soil is exceeded.
– 2. subsurface flow- lateral movement of water through the soil
– 3. groundwater flow- slow discharge of water from an aquifer into a stream
– 4. stream flow
• storage (S)
Geomorphology
Lake Formation• graben- downfaulted trough; e.g. Lake Tahoe
• caldera- subsidence of magma chamber; e.g. Crater Lake, OR
• Landslides
• glacial activity- e.g. scour, morain dams, & ice melt
• solution- CaCO3 (limestone)
• Oxbow
• wind- playa lakes
• humans & beaver
Oxbow Lake
Drainage Basin
Stream Type
1. ephemeral- channels not well defined; flow during and shortly after precipitation events
2. intermittent- generally flow only during the wet season
3. perennial- year round
spatial scale in lotic ecosystems
World
Continent
Drainage
Watershed
Stream
Sedimentation & Channel Patterns
• erosion- chemical and mechanical processes by which stream channels are formed
Deposition
process where particles that have been entrained and transported are deposited.
factors effecting deposition
1. stream gradient
2. flow volume
3. particle size
4. impoundments
results of deposition
• delta- results when flowing water meets standing water
• alluvial fan- sediments are deposited on land after eroding from higher elevation
• alluvial flood plain-
Delta
Alluvial Fan
Alluvial Floodplain
Flood Plain
Global Climatic Patterns
Global climatic patterns result from differential heating and cooling of the earth’s surface.
Winds and ocean currents redistribute energy over the earth.
Global Precipitation
Global Ocean Currents
Topographic Effects & Local Variation
riparian zones
xeric
mesic
outcrops
endemics
Riparian Zone
Xeric
Mesic
Rocky Outcrops
Soils
Four factors generally determine the characteristics of soils:
parent material climate
vegetation topography
Soil Horizons
O (litter)
A1 (humus-partially decomposed organics)
A2 (region of extensive leaching)
B (chemically resembles underlying rock)
C (slightly altered parent material)
Soil Horizons
Weathering
• “the physical and chemical alteration of rock material near the earth’s surface”
freezing
thawing
dissolution
oxidation