Plant Ecology Chapter 17 Climate & Physiognomy

Plant Ecology - Chapter 17

• Climate & Physiognomy

The Abiotic Components of Ecosystems

Outside Energy Source

Physical factors that determine weather, climate

Heat

Heat

Heat

Heat

Heat

Heat

• Daily temperatures can also vary dramatically in some habitats

• Deserts - dry air, loses heat rapidly

• High altitudes - thinner “blanket” of atmosphere

Heat

• Long-term changes in earth’s orbit, position

• Collectively produce Croll-Milankovic effects on climate

• Orbit shape change

• Affects range of seasonal variation

Heat

• Degree of tilt

• Affects range of seasonal variation

Heat

• Direction of the tilt - the “wobble”

• Changes which hemisphere is pointed toward sun when orbit is closest to sun

• Affects severity of seasonal shift

Wind and Precipitation

• Uneven heating

• Ascending, descending air masses - Hadley cell

Modifiers

• Rotation of the globe - Coriolis effect

• Hadley, Ferrel cells, jet streams

Modifiers

• Ocean currents, gyres induced by surface air mass movements

Modifiers

• Topography - mountains

• Rain shadows

Modifiers

• Topography - lakes

• Lake effect precipitation

Modifiers

Modifiers

Seasonal Patterns

Multi-year Patterns

Multi-year Patterns

• Combined ocean currents and jet stream

Multi-year Patterns

• Milder winters along US-Canada border

• Increased winter storms in California

• Floods in SE, snow in SW mountains

• Decreased hurricane activity in Atlantic

Multi-year Patterns

• More, stronger tornadoes in Midwest

• More, stronger hurricanes

• Drought, forest fires in SW

Plant Physiognomy

• North-south gradient in vegetation form due to temperature

• West-east changes in response to precipitation

Plant Physiognomy

• Evergreen broadleaf

• Deciduous broadleaf

• Evergreen coniferous

• Tree line

Plant Physiognomy

• Tree line climate can produce strange tree forms - krummholz

• Atypical 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 forest

• Changes in amount, seasonality of rainfall

Plant Physiognomy

• East of Rockies, start with short-grass prairie

• Low-growing clumps of grass with bare patches between clumps

Plant Physiognomy

• Gradual shift from midgrass prairie to tallgrass prairie in Nebraska/Iowa

• Taller grasses, forbs, more diversity and biomass

• Follows pattern of increasing rainfall

Plant Physiognomy

• Further east - trees appear in places other than along streams

• Woodlands - dominated by trees, but without a closed canopy (oak savanna)

Plant Physiognomy

• Forests appear near Illinois-Indiana border

• Continue 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 fire

• Still are more fire-tolerant species

Plant Physiognomy

• Precipitation in forests is high enough to keep fire frequency low