The Ecology of Tijuana Estuary, California: An Estuarine Profile

and height were lower than ever before recorded.
The delayed reaction of cordgrass tsl
measurements was due to the longevity of the
plant. Individual stems live 1.5-2.0 years, and the
1984 measurements included stems with some live
materlal from the previous growing season. By
1985, there were few plants from the previous year
and few individuals from 1985, even though tidal
flushing had been reinstated throughout the entire
growing season.
To interpret these variations in cordgrass
growth requires consideration of the effects of
hydrological change on pickleweed, because
pickleweed is the competitive dominant (Zedler
1982; Covin 1984) and its distribution overlaps
with cordgrass throughout most of the lower marsh.
Years of high pickleweed cover were 1979, 1981,
and 1984-85 (Table 26). These same years had
low cordgrass biomass. Cordgrass tsl can be high
when two conditions are met. First, there must be
appropriate salinity, nutrients, and soil moisture;
and second, there must be reduced competition
from pickleweed. The latter condition appears to
be associated with reduced drainage, that is.
increased inundation. Several experimental tests
of these hypotheses have been initiated.
5.4.1 Hydrology and Salinity Experiments
Figure 66. Changes in average height of cordgrass.
Means are based on the total number of stems
measured each year.
An experimental field study was initiated in
1984 to determine how coastal wetlands would
respond to increased streamflow caused by treated
wastewater. The data provide a test of the above
hypotheses concerning cordgrass responses to
salinity reductions at different times of the year. A
brief summary and pertinent findings follow from
the work of Beezley and Beare (SDSU, unpubl
data).
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Year
Figure 67. Changes in the maximurn height of Figure 68. Changes in the density of cordgrass stems.
cordgrass. Means are from the number of quadrats in Means are from the number of quadrats in which
which cordgrass was present each year (Figure 621. cordgrass was present each year (Figure 62).