Plant Ecology - Chapter 17

Climate & Physiognomy

The Abiotic Components of Ecosystems

1) Outside energy source1) Outside energy source

2) Physical factors that determine2) Physical factors that determine weather, climateweather, climate

3) Chemicals essential for life3) Chemicals essential for life

Outside Energy Source

PowersPowersphotosynthesisphotosynthesis

Warms earthWarms earth

Powers waterPowers watercyclecycle

Physical factors that determinePhysical factors that determineweather, climateweather, climate

HeatHeat

WindWind

PrecipitationPrecipitation

TopographyTopography

HeatHeatLocationLocation

ReflectionReflection

RetentionRetention

HeatHeat

HeatHeat

HeatHeat

HeatHeat

HeatHeat

Daily temperatures can also vary dramatically in some habitatsDeserts - dry air, loses heat rapidlyHigh altitudes - thinner “blanket” of atmosphere

HeatHeat

Long-term changes in earth’s orbit, positionCollectively produce Croll-Milankovic effects on climateOrbit shape changeAffects range of seasonal variation

HeatHeat

Degree of tiltAffects range of seasonal variation

HeatHeat

Direction of the tilt - the “wobble”Changes which hemisphere is pointed toward sun when orbit is closest to sunAffects severity of seasonal shift

Wind and PrecipitationWind and PrecipitationUneven heatingUneven heating

Ascending, Ascending, descending air descending air masses - masses - Hadley Hadley cellcell

Slide 13Slide 13Slide 13Slide 13Slide 13

Moist surface warmed by sun

Flows toward low pressure,picks up moisture and heat

Warm,dry air

Hot, wetair

Falls, is compressed, warms Rises, expands, cools

Heat releasedradiates to space

LOWPRESSURE

HIGHPRESSURE

Cool, dryair

Condensationand

precipitation

HIGHPRESSURE

HIGHPRESSURE

LOWPRESSURE

LOWPRESSURE

Figure 6-10Page 117

ModifiersModifiers

Rotation of Rotation of the globe - the globe - Coriolis Coriolis effecteffect

Hadley, Hadley, Ferrel cells, Ferrel cells, jet streamsjet streams

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Ocean Ocean currents, currents, gyres gyres induced by induced by surface air surface air mass mass movementmovementss

ModifiersModifiers

TopographTopography - y - mountainsmountains

Rain Rain shadowsshadows

ModifiersModifiers

TopographTopography - lakesy - lakes

Lake effect Lake effect precipitatiprecipitationon

ModifiersModifiers

Annual precipitation

ModifiersModifiers

Seasonal PatternsSeasonal Patterns

Multi-year PatternsMulti-year Patterns3-7-year El NinoSouthern Oscillation

Multi-year PatternsMulti-year Patterns

Combined Combined ocean ocean currents currents and jet and jet streamstream

Multi-year Patterns

Milder winters along US-Canada borderIncreased winter storms in CaliforniaFloods in SE, snow in SW mountainsDecreased hurricane activity in Atlantic

El Nino

Multi-year Patterns

More, stronger tornadoes in MidwestMore, stronger hurricanesDrought, forest fires in SW

La Nina

Plant Physiognomy

North-south gradient in vegetation form due to temperatureWest-east changes in response to precipitation

Plant Physiognomy

Evergreen broadleafDeciduous broadleafEvergreen coniferousTree line

Plant Physiognomy

Tree line climate can produce strange tree forms - krummholzAtypical growth pattern resulting from borderline growth conditions - mean annual soil temps. <5-8°C, air temps. ~10°C

Plant Physiognomy

Gradual transition from west to east, grassland to woodland to forestChanges in amount, seasonality of rainfall

Plant Physiognomy

East of Rockies, start with short-grass prairieLow-growing clumps of grass with bare patches between clumps

Plant Physiognomy

Gradual shift from midgrass prairie to tallgrass prairie in Nebraska/IowaTaller grasses, forbs, more diversity and biomassFollows pattern of increasing rainfall

Plant Physiognomy

Further east - trees appear in places other than along streamsWoodlands - dominated by trees, but without a closed canopy (oak savanna)

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Plant Physiognomy

Forests appear near Illinois-Indiana borderContinue to the east coast

Plant Physiognomy

Seasonality of precipitation (spring and fall) and warmer temperatures increase chance of drought in grasslands

Plant Physiognomy

Mid-, tall-grass prairies experience fire every 3-5 years (too little combustible material in short-grass prairie)Trees can’t survive frequent fires (apical meristems)

Plant Physiognomy

Woodlands appear where fire frequency is low enough to allow trees to grow tall enough to avoid fireStill are more fire-tolerant species

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Plant Physiognomy

Precipitation in forests is high enough to keep fire frequency low