| |
Changes in plant cover are a feature
of many wetland habitats and can occur through natural events like
wrack deposition
or through anthropogenic activities like invasion, restoration or
flushing regime changes. My research focuses on identifying the
importance of this
changing plant cover on wetland structure and function.
|
|
| |
| . |
|
|
Salt
marsh
vascular
plant
regulation
of
microalgal
and
infaunal community structure
In this experiment, we manipulated light and
plant cover to determine how vascular plants interact with benthic
microalgae and invertebrate communities. Clipping and shading
manipulations, designed to mimic the effects of vascular plant presence
and absence and their shading effects, revealed that plants exert
strong influence on abiotic environmental factors (salinity, water
content, and temperature at the soil surface) that mediate changes in
the biotic community. In the absence of plants, soils exhibited higher
temperature and salinity, and lower water content than those in
unclipped controls or shaded patches. The algal mats experienced
greater mortality in the unshaded treatment and increased thickness in
the shaded plots whose plants were removed.
|
Early successional stage infaunal communities
resembled communities seen in an early stage marshes; they had lower
species richness, a larger proportion of insect larvae and a smaller
proportion of annelids than when plants remain (control) or their
shading effects are removed. This experiment demonstrates the dramatic
effect of light reduction by the vascular plant canopy on the abiotic
environment as well as on the infaunal community. This research will
help elucidate the trophic ecology of salt marsh animal communities in
general and the implications of changing plant cover associated with
marsh restoration or plant invasion.
|
| . |
Impacts
of invasion: tamarisk (Tamarix.
spp.)
One of the most problematic invaders in the
western United States has been salt cedar, Tamarix spp.. The
impacts of this species in riparian and desert ecosystems have been
well-documented. We are researching the impacts of large populations of
tamarisk in the
intertidal salt marshes of Tijuana River
National Estuarine Research Reserve, a habitat not often considered
vulnerable to invasion by tamarisk. Initial research demonstrates that
there are multiple species and hybrids of Tamarix invading
the estuary and that the potential impact of tamarisk within this salt
marsh is significant, particularly on salt marsh food webs.
|
|
| ... |
|
Impacts of invasion:
perennial pepperweed (Lepidium
latifolium)
Perennial pepperweed (Lepidium latifolium,
LELA)
is
an
aggressive,
non-native
weed
that
has invaded wetland and riparian
areas throughout California. At Rush
Ranch, a brackish marsh in the San
Francisco Bay National Estuarine
Research Reserve, we applied a two-pronged approach to
understanding
and managing pepperweed: (1) mensurative experiment documenting impacts
of perennial pepperweed on the sediment community and food web, and (2)
eradication experiments evaluating efficacy and non-target impacts of
herbicide control in a seasonal wetland. Preliminary results
indicate altered the diversity and composition of the surrounding plant
and insect communities. In addition, we are evaluating potential
impacts of LELA on the Suisun song sparrow.
|
| .. |
Response of benthic
communities to changing
flushing regimes in a Southern California lagoon
The Southern California coast is dotted with
coastal lagoons and embayments. Typically, geographically small with
episodic freshwater input linked to rain events, these lagoons
sometimes close for extended periods or during specific reproductive
seasons, possibly causing key species with life cycles dependent on
ocean flushing and transport to disappear. The objective of this
research was to determine responses of the seagrass, Ruppia
maritima L. and associated benthic communities to changing ocean
flushing conditions in San Dieguito Lagoon. With loss of R.
maritima cover, porewater salinity increased, porewater
temperature decreased, and sediment redox values became more positive.
Multivariate analysis indicates differences in the invertebrate
community related to the presence of Ruppia, potentially as a
detrital food source.
|
 |
|
Photo: M. Alloush
|
Evaluating
functional recovery of a restored
coastal wetland in southern California (with B. Allen, C Lowe)
Our study will characterize the structure and
function of two wetland landscapes in the Huntington
Beach Wetlands before a major restoration
project begins in Brookhurst Marsh. Within each landscape we will (a)
detail the physical parameters of sediment communities, (b) quantify
benthic plant, algal, and faunal diversity, with special note of
invasive species, (c) characterize the trophic pathways that link the
primary producers and consumers, and (d) quantify fish use of newly
created channel habitat within the marsh.
|
| .. |
Evaluating restoration planting regimes
(with E. Blair, B. Allen)
Currently, it
is understood that following a
restoration event, marsh succession is highly contingent on the amount
of plant
cover within a communit. In a high marsh berm community in Huntington
Beach Wetlands, we are evaluating the recovery of plant, microalgal,
and invertebrate communities following poly- and monoculture
plantings.
Photos: E. Blair
|
|
