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