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Lecture 9

BIO120H1 Lecture Notes - Lecture 9: Temperate Deciduous Forest, Climax Community, Spatial Ecology

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Jon Abbatt

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Lecture 9: Spatial ecology, plant communities, and disturbance
Disturbance: An event that causes rapid or marked change in a population or
community often thought of as displacing an ecological system from its
equilibrium.( E.g.: fire, windstorm, logging, agriculture)
Succession: a regular sequence of changes in the species composition of a community in
a newly forms or disturbed habitat that progresses to a stable state.
Climax community: the end point of a successional sequence, or sere; a community that
has reached a steady state under a particular set of environmental conditions
Sere: a series of stages of community change in a successional sequence leading toward
a stable state
Primary succession: new substrate created, no pre-existing vegetation
Secondary succession: pre-existing vegetation undergoes a disturbance
Stages of successional change
1. Soil development: solid lava breaks down into finer particles, dead plants contribute
organic matter.
2. Plants attract birds; birds bring in seeds
3. Herbaceous plants cover ground, trees grow
4. Tree canopy closes in, soil is well developed, and shade becomes important
Secondary succession in temperate deciduous forest biome: Koffler Scientific Reserve
Old-field succession, year 1: Annual weeds
Old-field succession, stage 2: Perennial weeds
Old-field succession, stage 3: Woody shrubs move in
Old-field succession, stage 4: Tree saplings
Old-field succession, stage 5: Tree canopy closes in
Old-field succession, stage 6: Shrub layer thins out
Old-field succession, stage 7: Only shade-tolerant spp. remain
Drivers of terrestrial succession
Soil development, especially accumulation of organic matter, N content, pH buffering,
water retaining capacity (especially important in primary succession)
Shading (especially important in secondary succession, where soil is already developed);
shade-tolerant species replace shade intolerant ones
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