Agriculture Reference
In-Depth Information
100.000
(a) Postfire chaparral
Ec
= 7.67
(b) Postfire chaparral
Ec
= 10.82
10.000
1.000
0.100
0.010
0.001
100.000
(c) Mature chaparral
Ec
= 2.11
(d) Mature chaparral
Ec
= 1.73
10.000
1.000
0.100
0.010
0.001
100.000
(e) Australian heath
Ec
= 42.59
(f) Australian heath4
Ec
= 47.26
10.000
1.000
0.100
0.010
0.001
0 1020304050607080
Rank sequence
0 1020304050607080
Rank sequence
Fig. 11.4
Dominance-diversity curves for (a,b) Californian and (c,d,e,f) Australian shrublands
based on cover (from Keeley & Fotheringham
2003b
). Californian sites fit a geometric model
and Australian sites showed a significant fit to MacArthur's broken stick model. Ec, Whittaker's
equitability index.
species, being found in a very small fraction of quadrats within a site as well as
within a small fraction of sites (Keeley
et al.
2005c
). Based on dispersal capacity
this does not appear to be driven by metapopulation dynamics but rather micro-
habitat specialization.
In contrast, Australian heathland species are more equitably distributed, as
illustrated by their narrow species-abundance distribution and dominance-
diversity relationship that fits MacArthur's broken stick model (
Fig. 11.4c
,
d
).
The implication of this model is that populations reach a stable equilibrium
without the development of dominance by any one species (Whittaker
1972
). This
leads to an exponential species-area curve because most species in a community
are common and occur within a small subsample of the area, leading to a sharp
increase in diversity between 1 and 100 m
2
evident by a linear fit to a semi-log plot
