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Community organization and succession in rocky intertidal surfgrass beds

Succession and organization of rocky intertidal zone surfgrass beds
(Phyllospadix scouleri Hook) were examined experimentally at two sites
on the Oregon coast. The interaction of three attributes of the plant
-- high persistence, high preemption, and slow recovery -- strongly
influences the organization of surfgrass beds. Permanent plots indicate
that surfgrass is persistent. Comparisons of experimental surfgrass
removal and control plots demonstrate its preemptive ability, because
removal plots are invaded by many algal species, but these algae are
preempted from control plots. The slow growth of surfgrass rhizomes and
the slower recruitment of surfgrass seeds indicate its recovery ability
is low. The interaction of these phenomena produces a mosaic of
surfgrass and algae in different successional stages.
The successional sequence following a disturbance is more complex
than predicted by any simple model because of temporal and spatial
variation as well as differences in the species replacement mechanism.
In some plots the early colonists, the perennial brown algal blade
Phaeostrophion irregulare and the annual green algal blade Ulva sp.,
dominated for three years; in others they were replaced by a suite of
middle successional species including the branched red algae
Cryptosiphonia woodii. In other plots the slowest growing middle
successional species, the branched red alga Rhodomela larix replaced
other species. Part of this variability appears to be caused by large
waves in the fall and winter, which remove large areas of algal cover,
allowing dominant species to be replace by either earlier or later
successional species. Part of the variability appears to be caused by
local differences in the surfgrass understory before disturbance.
Rhodomela larix is usually not completely removed by disturbance and
regrows from its holdfast more readily than it recruits from spores.
The mechanisms by which later species replace earlier ones differ
depending on the successional stage. Established Phaeostrophion
inhibits Ulva and filamentous diatoms. In contrast, certain middle
successional species are necessary for seeds of the late successional
surfgrass to recruit. The barbed seeds become attached to algal species
with a central axis approximately 1 mm in diameter but not to algae with
other forms. / Graduation date: 1983
Date28 July 1982
CreatorsTurner, Teresa
ContributorsMenge, Bruce A.
Source SetsOregon State University
Detected LanguageEnglish

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