Recent evidence suggests that this 

 boundary is unstable and that competition 

 with pickleweed restricts the abundance of 

 cordgrass at its landward boundary. To 

 determine if distributional limits were 

 stable, Chris Nordby examined eight areas 

 along the upper boundary of cordgrass at 

 Tijuana Estuary (Zedler, Nordby and 

 Williams 1979). The study was done in 

 fall of 1979, following two wet years 

 (Chula Vista's rainfall was 39 cm in 1978 

 and 36 cm in 1979, compared to a 23- cm 

 average) . Comparing numbers of live and 

 dead stems, Nordby found that cordgrass 

 was expanding in five of the areas, 

 temporarily stable in one location and 

 receding in only two areas. Instability 

 was the rule", stability, the exception. 



The role that competition plays in 

 the abundance of cordgrass in this ecotone 

 was indicated in a 1981 field experiment 

 carried out near three of Nordby's study 

 plots. Removal of pickleweed from PjLots 

 which averaged 65 cordgrass stems/m in 

 February resulted in nearly a 3-fold 

 increase in numbers of cordgrass stems and 

 a 1.7-fold increase in biomass (Table 6). 

 The two species probably compete for both 

 light and nutrients. Differential 

 tolerance to salinities could shift the 

 competitive advantage toward pickleweed 

 during years of high salinity stress (i.e. 

 drought years) ; the upper limit of 

 cordgrass should recede in response to 

 high salinities, as well as reduced 

 competitive ability. During wet years, 

 both species would do well and cordgrass 's 

 rapid spring growth would allow expansion. 

 Additional features of these two southern 

 California marsh dominants are given in 

 the following section. 



Since the speculations of Edith 

 Purer, some forty years ago, we have 

 progressed relatively little in explaining 

 the distributional limits of species 

 across the intertidal zone. Future 

 research should recognize the dynamic 

 aspects of both the soil's environment and 

 species distributions, and it must consider 

 the importance of species interactions 

 under a variety of changing conditions. 



Experiments to determine the competitive 

 advantage of cordgrass and pickleweed over 

 a range of salinity and inundation regimes 

 are badly needed. Likewise, experiments 

 to assess the establishment ability of 

 annuals during short- and long-term 

 periods of wet, brackish soils are needed. 

 These experiments would be complex and 

 difficult to carry out because both the 

 timing and duration of freshwater 

 influence would have to be manipulated. 



2.2 COMMON SPECIES 



Macdonald (1977a) has summarized 

 autecological features of seven common 

 California halophytes, and the anatomical 

 descriptions given by Purer (1942) have 

 yet to be improved upon. Hence this 

 discussion will emphasize recent 

 information about the most common southern 

 California marsh plants, proceeding from 

 low to high marsh. 



Cordgrass ( Spartina foliosa ) (Figure 

 13) forms robust stands in the lowest 

 elevations of most tidally flushed 

 wetlands. At Tijuana Estuary densities 

 averaged 60 stems/m ; heights averaged 0.8 

 to 1.5 m; and August standing crops were 

 1.0 to 1.4 kg/m in 1980. All values are 

 for nrlOO plots between 3 and 6 dm MSL 

 (decimeters above mean sea level) (Zedler 

 unpub. ms.) and represent growth under 

 unusually good conditions. 



Because of the importance of 

 cordgrass as habitat (Jorgensen 1975) for 

 the endangered light-footed clapper rail 

 ( Rallus longrirostris lev i pes ).consider able 

 attention has been given to the artificial 

 propagation of this species. Although 

 Phleger (1971) was unable to germinate its 

 seeds, Seneca (1974) and Mason (1980) 

 achieved success with seeds from San 

 Francisco Bay populations; and several 

 populations have yielded viable seed in 

 San Diego County (Zedler 1981a). 

 Seedlings are extremely rare in nature, 

 however, and most of the spread of the 

 species is vegetative. Transplantation 

 has been successful in expanding the 

 species' local distribution, suggesting 



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