superorganism community concept

1
(No Transcript)
2
(No Transcript)
3
(No Transcript)
4
superorganism community concept Clements argued
that because of interactions between species
during the climax phase of succession and because
of facilitation during seral stages, plants and
animals are bound together into tight communities
that behave like superorganisms. In this view,
all of the species in a community are like the
different organs of a larger organism. All the
species depend on the functioning of the other
species in the community and cannot persist
outside of this association. One attraction of
the superorganism model is that it allows
biogeographers to assume that the community types
that are described and mapped are stable features
of the biosphere.
5
individualistic community concept H.A. Gleason
argued that what we perceive as biological
communities are simply areas of similar habitat
where species coexist because they have somewhat
comparable environmental tolerances and resource
demands. Gleason argued that each of these
species has its own individual sets of tolerances
and demands and do not always occur together.
Since the species do not always have to occur
together, communities cannot be thought of as
superorganisms.
6
(No Transcript)
7
(No Transcript)
8
To simplify descriptions, plant biogeographers
and foresters often describe associations in
terms of the dominant plant species and call such
associations dominance types
9
In conducting surveys of stands, samples of
species composition are often made by laying out
square subsampling areas called quadrats. If
the quadrat is too small, it will not capture all
of the true species diversity of the stand. If
the quadrat it is too large, it takes too long to
sample and yields no additional information on
species diversity. When sampling large areas,
or examining dominant tree species only, line or
belt transects are often used. A line through the
stand is surveyed and all trees touching it, or
growing within a certain distance of the line,
are identified and recorded.
10
Quadrats normally consist of a square frame, the
most frequently used size being 1m2
As a general guideline, 0.5 - 1.0m2 quadrats
would be suggested for short grassland or dwarf
heath, taller grasslands and shrubby habitats
might require 2m quadrats, while quadrats of 20m2
or larger, would be needed for woodland habitats.
At the other end of the scale, if you are
sampling moss on a bank covered with a very
diverse range of moss species, you might choose
to use a 0.25m2 quadrat.
11
Systematic sampling is when samples are taken at
fixed intervals, usually along a line. This
normally involves doing transects, where a
sampling line is set up across areas where there
are clear environmental gradients. For example
you might use a transect to show the changes of
plant species as you moved from grassland into
woodland, or to investigate the effect on species
composition of a pollutant radiating out from a
particular source . Line Transect Method A
transect line can be made using a nylon rope
marked and numbered at 0.5m, or 1m intervals, all
the way along its length. This is laid across the
area you wish to study. The position of the
transect line is very important and it depends on
the direction of the environmental gradient you
wish to study.
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
(No Transcript)
34
(No Transcript)
35
(No Transcript)
36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
39
(No Transcript)
40
(No Transcript)
41
(No Transcript)
42
(No Transcript)
43
(No Transcript)
44
(No Transcript)
45
(No Transcript)
46
(No Transcript)
47
(No Transcript)
48
(No Transcript)
49
(No Transcript)
50
(No Transcript)
51
(No Transcript)
52
(No Transcript)
53
(No Transcript)
54
(No Transcript)
55
(No Transcript)
56
(No Transcript)
57
(No Transcript)
58
(No Transcript)
59
(No Transcript)
60
(No Transcript)