Biology Reference
In-Depth Information
a
California
Stillwater Cove
Sites 1-3
b
c
Both kelp
canopies
Both kelp
canopies
No kelp
canopies
No kelp
canopies
20 m
Desmarestia
10 m
Macrocystis
Macrocystis
Fig. 7.1
Diagram of kelp canopy clearing experiment used by Clark et al. (
2004
) showing (
a
)
location of the three replicate sites in Stillwater Cove, CA, USA. (
b
) Blocked canopy clearing
design showing the 20 m radius inner circles and 10 m radius outer tori from which kelp canopies
were removed either individually or in combination. Treatments include “No canopies”
¼
both
Macrocystis
and
Pterygophora
removed, “
Pterygophora
canopy”
¼
Macrocystis
removed and
Pterygophora
left unmanipulated,
“
Macrocystis
canopy”
¼
Pterygophora
removed and
Macrocystis
left unmanipilated, and “Both canopies”
both kelp species left unmanipulated
(also considered as control treatment). (
c
) Canopy clearings showing the placement of the
Desmarestia
removal treatment following dense
Desmarestia
recruitment. Diagram reproduced
from Clark et al. (
2004
)
¼
Harger (
1985
) and Reed (
1987
). Consequently, as the dominant kelps begin to
recover following a disturbance, they often recruit in much higher densities than
can be sustained when they are adults and thus undergo strong intraspecific compe-
tition (i.e., density dependence) that results in self-thinning of the population
(Fig.
7.3
). However, large variability exists in the interpretation of how important
density dependence is to algal populations, in part due to differences in the experi-
mental methodologies used to examine it (Flores-Moya et al.
1996
; Scrosati
2005
).
