2011 lecture 4b ecosystem dynamics ii
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8/7/2019 2011 Lecture 4b Ecosystem Dynamics II
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Ecosystem Dynamics II
NR216 Introductory Ecology
February 1, 2011
E&FB Ch 20, 21, 22 & 23
Kimmins Balancing Act Chapter 5 pp. 17 - 20
8/7/2019 2011 Lecture 4b Ecosystem Dynamics II
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Focus is on
Community Dynamics
Ecosystems and their communities change -
over distance &
over time
which leads to :
Patterns of Zonation & Succession
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Patterns of Zonation & Succession
FOUR PRINCIPLES
1. The fundamental niche of a species is the
most important factor :
where does it grow (distribution) &how much is there (abundance)
2. Species vary in their fundamental niches because
they have different sets of environmental tolerances
3. environmental conditions change in both time &space
4. Species interactions affect the fundamental niche
(realized niche)
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Community Dynamics:
Patterns of Zonation
Zonation : change over distance in response to
environmental gradient ie.
Temperature Moisture
Elevation & altitude
LatitudePatterns of zonation in a salt marsh E&FB p. 405
Distribution of tree species along an elevational transect E&FB p.399
8/7/2019 2011 Lecture 4b Ecosystem Dynamics II
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8/7/2019 2011 Lecture 4b Ecosystem Dynamics II
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Community Dynamics:
Patterns of Zonation
Ecocline :
the sequence of biotic communities & associated physical environment
along a major environmental gradient, like
elevation or latitude
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Community Dynamics:
Patterns of Zonation
Clinal Variation (in species) :
Variation in physiological characteristics such
as time of bud flush of plants/trees orseasonal coat colour change of some animals
Genetic basis
Seasonal fluctuation Diurnal variation
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Community Dynamics:
Patterns of Zonation
Ecotone :
The interface or zone of transition between
two plant communities that differ in life formor in species composition, or both.
A zone of tension between two different
communities characterized by higher
environmental, species & structural diversity
than the adjacent communities
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Community Dynamics:
Patterns of Zonation
Site:
Any physical or chemical condition or factor that sets thepotential for vegetation development, net PP andaccompanying animal & microbial communities.
ie.
soil & geology
topography (aspect/slope, slope position, elevation)
slope stability
hydrology
cold air drainage & frost pockets
fire risk
wind exposure
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Community Dynamics:
Patterns of Zonation
Classify Site :
Site Index tree growth potential
Ecological Land Classification vegetationcommunity potential
Wildlife habitat potential
Some other objective or goal forforest/watershed/land management
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Change over time :
Ecological Succession
Process of change in an ecosystem, over time
Complex interactions among plants, animals &
microbes (ie. pioneering species may make iteasier for other species to grow or may make
it difficult for other species to grow;
sometimes both)
Sere or seral stage = product of succession
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Change over time :
Ecological Succession
A sere is the sequence of ecosystems that
successively replace each other on a given
area of land, over time.
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Change over time :
Ecological Succession
Each stage in that sere :
Different plant associations (species
composition & community structure) Different age structure of dominant
vegetation (ie. even-aged, un-even aged trees)
Different microclimate, soil, forest conditions Different animal communities
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Change over time :
Ecological Succession
Pioneering stage Mid-seral stages Late seral stages
Pioneering Transitional Sub-climax Climax
relatively stable self-replicating
reproduce in own
shade
uneven-aged same species mix &
balance
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Change over time :
Ecological Succession
Primary succession from bare rock or water(E&FB pp.408ff.) more
Secondary succession reestablishment aftershort-term disturbance more
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Change over time :
Ecological Succession
Strongly influence by what was there before
(root sprouts, seed banks)
Xerarch = dry/xeric
Edaphic = soil (dry or wet and/or acidic)
Mesarch = mesic
Pyric = fire (cyclical climax) Hydrarch =wet/hydric
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Change over time :
Ecological Succession
Autogenic succession : E&FB pp.434-437
Change caused by modification of
environmental by plants growing there
ie. bog forest
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Change over time :
Ecological Succession
Biogenic succession :
animals/insects affect which plants survive
ie. spruce budworm
Tent caterpillar
grazing herbivores elephants
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Change over time :
Ecological Succession
Allogenic succession : E&FB pp.441-443
Change caused by changes to the environment
independent of living organisms Climate change
Glaciation
Sedimentation in freshwater lakes moredeep lake shallow lake
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Disturbances at the Landscape LevelE&FB Ch. 23
Typical landscape is
a mosaic of communities
at different successional stages and
occupying different habitats.
Rich, dynamic tapestry of vegetation,
providing an array of habitats for animals & microbes
(Perry, Forest Ecosystems, p.169)
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Dynamics at the Landscape LevelE&FB Ch. 23
Landscapes are composed of numerous
community types
Corresponding to changes in elevation, aspect
& soils
Zonation
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Dynamics at the Landscape LevelE&FB Ch. 23
Patterns of disturbance and change over time
overlay this with another pattern; succession sequence and timing
is not always predictable.
Succession
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Disturbances at the Landscape Level
fire (can be cyclical)
water, wind, (flooding, erosion)
volcanic eruption, landslides/avalanches
frost damage, insect/disease, harvesting
pollution (ie. acid rain)
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Disturbances at the Landscape Level
Mosaics of patches (E&FB p.450)
more
Practices across landscapes - Canada's ForestsEcosystem-based management - Canada's Forests
Edges (E&FB pp. 451-455) moresalt marshes
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Disturbances at the Landscape Level
Disturbance major factor in ecosystems,
especially in forests
Originate from ± outside the ecosystem (ie. fire) or from
± within the ecosystem (ie. native insect outbreaks);
± often disturbances interact (ie. weather affects
susceptibility to in populations of insects, insect
damage increases incidence of fire)
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Disturbances at the Landscape Level
Fire most common disturbance in wide variety
of forest types :
Coniferous forests of N, W & SNorth America more
Eucalyptus forests of Australia more more
Dry tropical forests in South Africa& North America
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Fire Ecology
Factors affecting natural fires :
Time of year
Quantity, condition & distribution of fuel
Prevailing climatic conditions (rain, wind,temperature)
Slope, aspect & elevation
Type of vegetation (species, species habit,age)
Type of soil
Sever ity & int ensity of fi re
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Fire Ecology
3 major Types of Fi res;
can occur in any combination
Ground fires
Surface fires
Crown fires
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Fire Ecology
Ground fires
Largely flameless
Burns in OG matter/duff Can be most destructive because kills &
consumes roots, preventing root sprouts
Kills dormant seeds banked in site
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Fire Ecology
Surface Fires
Move quickly, burn litter & above-ground
portions of herbs & shrubs Often sprouting from roots after
Often doesnt kill trees, esp. those with thicker
bark
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Fire Ecology
Crown fires
Burns crowns of woody vegetation
Often leaves most of woody stems & forestfloor untouched
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Fire Ecology
Technical Terms :
Intensity rate of energy released
Severity impact on organic matter Rate of spread speed leading edge travels
downwind
eg. High intensity/low severityFrom Ashes to Forest by Tony Ianzelo - NFB
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