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BIO120H1 Lecture Notes - Lightning, Conifer Cone, Pioneer Species

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Ingrid L.Stefanovic

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L09- BIO 120
Science also perceives with theories, and generalization
Biological integration species playing a role with another (depend on each
Inidividualistic hypothesis- the reason species work together b/c they have
similar ranges of tolerancesame temp, habitat..etc
How were the conflicting hypotheses (Clements vs. Gleason) tested?
Invective, and decades later, by data (gradient analysis- )
Graph D is what whitticher found on slide 9. Each pseices behaves
individualistically, do not respond to each others presence but the
envornment conditions that vary.
Another piece of evidence- post-glacial migrations of tree species. Howveer,
different tree specied went along different path, they differently.
Vegetation is PRIMAILY INDIVIDUALISTIC: envornment affects them not
the presence of other vegetation.
Pioneer species(stars with r-strategists) seral stagesclimax stage (end)
Plants attract birds, bird bring in seeds new colonists to keep succession
moving along.
Primary succession- new species colonizes a placeeventually grow into a
lot more vegetation
Secondary succession: disturbance is caused (fire, logging), and then
vegetation grows back.
Annual plantsPerrenial weeds woody shrubssmall trestrees with
closed canopyshrub layers goes away(only shade-tolerant shrubs remain.
Sometimes you dont get a stable climax! Such example are: boreal forest;
acid,sandy soils; fire-prone ecosystems; systems driven by seasonality,
cycling of dominants (A replaces B, the B replace A);transient substrates
(decay of log)
Pine forest is at a flammable stage when pine cones cover ground (serve as
fuelignited by lightning from a storm)
Two kinds of fires:
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