Plant Ecology Chapter 17 Climate & Physiognomy


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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



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



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



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



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



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