Agriculture Reference
In-Depth Information
35
Woody-N
Woody-S
r
2
= 0.974
30
Herbs-N
r
2
= 0.979
25
Herbs-S
20
r
2
= 0.974
15
10
r
2
= 0.986
5
0
0.1
1
10
Area (m
2
)
100
1000
10 000
Fig. 11.5
Species-area relationships for different growth forms (N and S refer to slope aspect;
from Pausas
et al.
1999
) and similar patterns have been observed in California chaparral
(Keeley & Fotheringham
2003b
).
(
Fig. 11.3
). An important contributor to these patterns is the fact that these
heathlands are dominated by perennials, and more than three quarters are
resprouters (George
et al.
1979
). Thus, following fire there are fewer opportunities
for community reassembly and less chance of dominance by one or a few species.
Thus, comparing the species-area curves between communities provides some
insight into the compositional differences in functional types. Those types deter-
mining the exponential vs. power model are evident even when the species-area
relationship is observed within communities. For example, woody plants typically
follow a different species-area relationship from herbaceous species (
Fig. 11.5
).
The climate, fire, geology filter controlling different fire-response functional
types in these MTC ecosystems appears to be strongly influenced by soils. The
more fertile Mediterranean Basin shrublands match Californian communities
closely in their species-area power law fit (Pausas
et al.
1999
) and dominance-
diversity relationships (Basanta
et al.
1989
). In contrast, the low-fertility South
African fynbos resembles Australian heathlands in its fit to an exponential model
(Bond
1983
; Cowling
1983b
; but cf. Schwilk
et al.
1997
).
Landscape Effects on Community Diversity Patterns
Landscape variation in resources is an important environmental filter in commu-
nity diversity patterns (Keeley
et al.
2005c
) and is likely a primary factor respon-
sible for the wide disparity in 0.1-ha scale species richness, ranging from 10 to 180
in the MTC communities surveyed in
Table 11.2
. Fire increases light and nutrients
