Frederic Clements

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Last Time
Frederic Clements The Dev. of vegetation can be
seen as a sequence of stages resembling the
development of an individual organism reaching
towards a climax stage -Ecological
Succession Primary Secondary
.
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Today
Some Updates Opposition to Clements Henry
Gleason (Opposition to Clements)
Vegetation as a Continuum Plant
formations What is Vegetation
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But First, Carols Comment
Ecological Succession in a Glacial Lake V
Spring Fed Lake
Lake in-filling or Eutrophication
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Matt and Paulas Question Acacia holosericea
A Successful Newcomer for the Dry Tropics from
its Native Australia !
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Matt and Paulas Question Acacia holosericea
Excellent for fuel, charcoal, animal fodder,
land rehabilitation, ornamental -in Africa and
the Indian subcontinent
In the Sudan
Niger
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Matt and Paulas Question Acacia holosericea
Excellent for fuel, charcoal, animal fodder,
land rehabilitation, ornamental -in Africa and
the Indian subcontinent
Charcoal Depot
Feed and Shade
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Opposition to Clementsian Theory
Fault with aspects of Clements's theory of The
dev. of vegetation, particularly his concept of
plant formation that the vegetation of a
given area is itself a living organism subject
to growth, maturity, and decay
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What is a Plant formation? -broad physiognomic
units (the vegetation of a given area) (-when
animals are included Biome) Examples of Plant
Formations Tropical Rainforest, Temperate
Deciduous Forest, Mid-latitude Grassland
etc. Clements stressed climate at the expense of
other factors in determining types of vegetation
growing in an area.
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Plant formation The definition of a plant
formation has nothing to do with the component
species, it is simply based on physiognomy
(general appearance).
For Example Plant formation in different areas
of the world may consist of very different
species, for example, the so-called Mediterranea
n-type vegetation of southern Europe, California
, Central Chile, southern Africa, and
southwestern Australia.
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Opposition to Clements Henry Allen Gleason
(1882-1975) (BA, MA U of Illinois) Botanist,
plant geographer, and ecologist. He developed
theindividualistic' or 'continuum' concept of
plant associations
Argued that Clements' view was overly
simplistic that individual species have
individual responses to environmental factors.
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Henry Allen Gleason
In 1926, H.A. Gleason published an important
paper "The Individualistic Concept of the
Plant Association. Revised the paper in
1939 He made four important points
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• Every species has more reproductive capacity than
• is needed to ensure the next generation survives.
• e.g. an oak tree during its lifetime will produce
• millions of acorns when only one successful acorn
  is
• needed to maintain the population.

2. Each species has some means of dispersing its
seeds or fruits. So some viable seeds or fruits
will exist beyond the present range of the
species.
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3. The environment is constantly changing on a
range of time scales, seasonally,
inter-annually, decadally, etc.
4. The development of a new association
depends upon the creation of new ground, or the
removal of pre-exisisting vegetation.
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All of this led him to conclude " ... it may be
said that environment varies constantly in time
and continuously in space environment selects
from all available immigrants those species which
constitute the present vegetation, and as a
result vegetation varies constantly in time and
continously in space."
There was little hard evidence to support his
thesis
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In essence, Gleasons view represented an
individualistic concept rather than a community
concept.
Clements-Communities
Gleason-individualistic
The continuum approach is more realistic than the
cummunity type approach.
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Gleason's ideas are embodied in disturbance
theory -suggests the straight line
trajectories implied during the successional
track of communities are much more complex. In
fact, disturbances are continually occurring to
create a mosaic of patches of communities across
the landscape.
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straight line trajectories..
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Pattern of Change-Directional
Middleton, N., 2003. The Global Casino. Hodder
Arnold, London.
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Patterns of Change - Episodic
Middleton, N., 2003. The Global Casino. Hodder
Arnold, London.
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Patterns of Change - Cyclical
Middleton, N., 2003. The Global Casino. Hodder
Arnold, London.
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Patterns of Change - Constant
Middleton, N., 2003. The Global Casino. Hodder
Arnold, London.
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Patterns of Change - Catastrophic
Middleton, N., 2003. The Global Casino. Hodder
Arnold, London.
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• Disturbance mechanism
• Fires (Mt Vision Fire, 1995)
• We will see this on the Point Reyes Field Trip,
• wind storms, volcanic eruptions, logging,
• climate change, severe flooding, disease,
• and pest infestation.
• These disturbances operate across certain
• temporal and spatial scales, and emphasize the
• complexity of responses by organisms to
• changes in the environment.

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• So, which theory is more accurate?
• Well, both really, depending on the community
• one is investigating.
• We should keep in mind that some communities
• we see and study are of relatively recent origin,
  
• some having derived since the end of the last
• glaciation about 10,000 years ago.

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• So, which theory is more accurate?
• These communities would seem very simple
• and easy to classify, given they've had little
• time to evolve.

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• Contrast this with communities that never
• suffered from glaciation, such as the tropics.
• These communities have had many millennia
• to evolve and are therefore more complex.

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What is Vegetation?
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What is Vegetation?
Describing can be very subjective!
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Vegetation Maps
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Vegetation Mapping
Some vegetation maps are based simply on
physiognomy others also include some floristic
information.
Vegetation mapping is one way of classifying
vegetation into varies "types."
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Vegetation Mapping
Kuchler gets around this problem by mapping
what he believes would be the vegetation of an
area if no humans were present.
Kuchlers Natural Vegetation of California
map illustrates this approach.
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What is Vegetation? The word "vegetation" is
simply a collective noun for the plant life of a
particular area. Definition of Vegetation is
the regional analysis of plants ecological
description of plant forms, including indication
of dominant species, predominant ecological
types, etc.
Natural?
Cultural?
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What is Vegetation? The study of vegetation
involves the synecological (study of the
ecological interrelationships among communities
of organisms) rather than the autecological
(branch of ecology that deals with the biological
relationship between an individual organism or an
individual species and its environment) approach.
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What is Vegetation? On the other hand, one can
view vegetation as consisting of a loose
assemblage of species, each species having its
own ecology and history.
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• What is Vegetation?
• In order to appreciate this point, we should
  recognize that there are two fundamentally
  different approaches to the study of vegetation
• the approach that assumes that vegetation can be
  subdivided into a finite number of types or
  units and
• (2) the approach that assumes that vegetation
  consists of a loose assemblage of species whose
  individual importance varies continually in time
  and space.

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• What is Vegetation?
• In order to appreciate this point, we should
  recognize that there are two fundamentally
  different approaches to the study of vegetation
• the approach that assumes that vegetation can be
  subdivided into a finite number of types or
  units and
• (2) the approach that assumes that vegetation
  consists of a loose assemblage of species whose
  individual importance varies continually in time
  and space.