Plant Ecology - Chapter 20

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Plant Ecology - Chapter 20

• Paleoecology

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Paleoecology

• The study of historical ecology
• Changes in global patterns of vegetation,
  diversity
• Driven by ecological, evolutionary processes

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Paleoecology

• Plants invaded land during the Paleozoic era,
  during the later Ordovician and Silurian
• Major time of evolution, diversification

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Paleoecology

• Diversity of biotic interactions developed early
• Mycorrhizae, herbivory, animal pollination,
  animal seed dispersal

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Paleoecology

• Fossil carbon deposits formed from plants during
  Carboniferous period
• Coal from remains of wetland plants (ferns,
  mosses, gymnosperms)

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Paleoecology

• Oil, gas developed from mostly marine plankton
  (phyto-, zoo-), and maybe wetland plants
• Dramatic climate change at end of Carboniferous -
  drier - seed plants began to dominate

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Paleoecology

• Mesozoic era was time of major tectonic plate
  movement
• Encompassed Triassic, Jurassic, and Cretaceous
  periods

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Paleoecology

• Moved from supercontinent Pangaea to breakup into
  current continents
• Improved conditions for plant growth,
  diversification

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Paleoecology

• Ferns, seed ferns, gymnosperms became the
  dominant flora
• CO2 levels 3-4 X higher than today provided warm
  climate and plentiful CO2 for photosynthesis

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Paleoecology

• Decline in CO2 (248-65 mya) changed conditions
  for plants
• Cooler, more seasonality
• Changing climate and continental breakup led to
  development, diversification of angiosperms

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Paleoecology

• Asteroid impact at end of Mesozoic (65 mya, K-T
  boundary)
• Impact debris and/or massive fires led to massive
  animal and plant extinctions
• Dinosaurs, and 25-80 of N. Amer, plants (more in
  south, fewer in north)

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Paleoecology

• Continued decline in CO2 concentrations (chemical
  reactions during new mountain weathering)
  resulted in slow, re-evolution of new species of
  angiosperms
• Evolution of C4 grasses from C3 ancestors
• Do better at low CO2

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Paleoecology

• Recent trends?
• Global changes in CO2?
• Change in C3 and C4 plant abundance, distribution?

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Paleoecology

• Microfossils - pollen grains
• Macrofossils - leaves, stems, flowers
• Used to understand changing plant communities,
  changing climates

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Paleoecology

• Glacial and interglacial cycling
• 100,000 years
• Change in angle, degree of tilt of Earths axis

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Paleoecology

• Change in species present in MN from 22,000 ya to
  present
• Spruce, ash, birch
• Pine, elm, oak
• Grasses
• Now pines,oaks,sedges

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Paleoecology

• Can track shifts in species distribution through
  time