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Lecture 9

Biology Lecture 9 Article 3.docx

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Scott Browning

BIOLOGY LECTURE 9 The Ecology of Fire  Fire takes apart what photosynthesis has put together  Not something extraneous to life to which organisms must adapt, it is something that has emerged out of the nature of life on Earth  Its taxonomy reflects this diversity, with the various types of fires distinguished by the combustibles they feed on  Ground fire: burns organic soil  Surface fire: moves through grasses, forest litter, shrubs  Crown fire: goes through canopy of brush and woods  A burn can be all types of these fires – Resulting mix makes up a fire’s regime (statistical composite like climate)  Fire regime can hold many kinds of fires: but when grouped show diff patterns  Geographic conditions for regimes= rhythm of wetting + drying  Place must be wet enough to grow fuels and dry enough to burn  Regime concept IMP: orgs are no more “adapted to fire” than water They adapt to pattern of burning – a trait suitable to survive one kind of fire may not help another kind  Fires date back! Fossil fires in the form of fusain (fossilized charcoal), back to when plants first began colonizing  Major charcoal beds in Paleozoic have huge fractions from fossilized fires  Today: reverse, with buried biomass burned faster than being stores  Ancient role of fire is a selective presence (thanks to phylogenetics)  Pyrosphere realm of fire co-evolved with biosphere + atmosphere, change in one affects the others Fire + Life (flood/wind don’t)  Species don’t merely adapt to fire, they influence its character  Fire depends on a biotic matrix to sustain it and because communities accompany it, they change the way fire behaves  Many plants show adaptations for coping with fire:  Most involve a suite of traits that accommodate a suite of stresses Ex) Prairie grasses store most of the biomass underground  Some traits are more targeted to respond to influence of fire Ex) Thick bark, water dense leaves, seed banks – all shield vital features against wage of heat  Organisms slough off heat/respond quickly after  Aspen sucker after fire  Eucalypts report under bark, sending out new limbs to replace seared ones/ sucker from roots  Rerouting is a common feature, especially in areas with intensive browsing  Some traits rely on fire to assure organism’s reproductive success  *Serotiny: where plants store seeds in canopy of wax-sealed cones, woody capsules or inflorescences.  Coverings shield the seeds against pulse of flame, then open to release seeds  Some depends on heat/smoke to germinate seeds in soil Stimulate buds  Heat shock can crack open hard shells and free seeds or let water in
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