species have rather 

 distribution and (2) 

 overlap occurs (Vogl 1966, 

 (Figure 9) . 



broad ranges 

 a high degree 



Zedler 



of 

 of 

 1977) 



The most detailed vegetation surveys 

 have been conducted at Tijuana Estuary, 

 where species occurrences and cover were 

 recorded along with elevation, soil 

 conductivity, and other environmental 

 characteristics at 357 sampling points 

 (Zedler 1977). Summary of these data 

 (Figure 9) illustrates the changes which 

 occur with elevation. Distributions of 

 species at Tijuana Estuary are similar to 

 other large marshes, such as Sweetwater 

 Marsh (Mudie 1970), Mission Bay (Macdonald 

 1967), Upper Newport Bay (Vogl 1966, 



Massey and Zembal 1979), Anaheim Bay 

 (Massey and Zembal 1979), and Mugu Lagoon 

 (Onuf, unpub. data), with one major 

 exception. The lower elevations of all 

 except the marsh at Mugu Lagoon are 

 dominated by cordgrass ( Spartina foliosa ) . 

 The limited occurrence of cordgrass at 

 Mugu Lagoon may be due to habitat 

 elimination resulting from past dredging 

 activities. Most of the evidence suggests 

 that cordgrass was the typical low marsh 

 dominant in tidally flushed marshes of 

 southern California. It has disappeared 

 from Los Penasquitos Lagoon where it was 

 once abundant (Purer 19^2), and this too 

 is probably due to disturbance of tidal 

 flushing (Zedler et al. 1980). 



Figure 9. Distribution of the most common halophytes by elevation, at Tijuana 

 Estuary (Zedler 1977). Data from Anaheim Bay (Massey and Zembal 1979) were used 

 to extend the ranges of species beyond the 3- to 12-dm MSL range observed at Tijuana 

 Estuary. 



17 



