Figure 26. Alkali weed ( Cressa 

 truxlllensis) . Photo by P. Zedler. 



Figure 27. Dodder ( Cuscuta salina ) , 

 parasitic on pickleweed. Photo by 

 J. DeWald. 



flowering stalks are unmistakable features 

 of the species. Its distribution may 

 ■correspond with lower soil salinities, 

 though ecological studies are lacking. 



2.3 TRANSITIONAL HABITATS 



Habitats between the higher salt 

 marsh and coastal scrub or dune vegetation 

 have undergone so much disturbance that 

 their communities are difficult to 

 characterize. Perhaps the best 

 understanding of their former composition 

 can be obtained by extrapolation from the 

 marshes at Bahia de San Quintin. 

 Neuenschwander et al. (1979) identified 

 the transitional zone as the area inland 

 of the highest debris line. Marsh species 

 had lower abundance and several desert and 

 coastal upland species were present. 

 Dominant species, both on the basis of 

 frequency and cover, were Monanthochloe 

 littoralis , Salicornia subterminalis , and 

 Frankenia palmeri . The latter species is 

 known only from San Diego Bay in the U.S., 

 where it is rare. Lycium brevipes and 

 Atr iplex julacea were occasional, and 

 Euphorbia mesera , Distichlis spicata , 

 Allenrolf ea occidentalis , Dudleya 

 brittonii , Haplopappus venetus , and three 

 cacti were relatively rare in the 

 transition zone. 



Transitional areas at Tijuana Estuary 

 are likewise distinguishable by the 

 appearance of a large variety of species 

 not common to lower elevations. The main 

 difference is that many of them are 

 introduced weeds. They grow among the 

 Salicornia subterminalis and shoregrass 

 ( Monanthochloe littoralis ) wherever soils 

 are low in salinity. 



2.4 SIMILARITIES WITH OTHER PACIFIC 

 COASTAL SALT MARSHES 



Macdonald (1977a) separates the 

 California marshes into three groups 

 (northern, San Francisco Bay, and southern 

 marshes) on the basis of species 

 composition. Information on soil 

 salinities is sparse,' but higher rainfall 



33 



