elevational range, and their distributions 

 overlap considerably in most marshes. 

 Small- scale boundaries between different 

 dominants result from their vegetative 

 mode of reproduction. Still, a pattern of 

 compositional change with elevation can be 

 seen, because the elevation of greatest 

 abundance differs among the nine most 

 common species (cf. Figure 9). Cordgrass 

 ( Spartina foliosa ) dominates the lowest 

 elevations; pickleweed ( Salicornia 

 virginica) is a major dominant through low 

 and middle elevations; a number of other 

 succulents and low-growing perennials 

 become common in middle and high 

 elevations. Transitions from intertidal 

 marsh to coastal scrub vegetation are 

 usually highly modified by disturbance and 

 several introduced weeds intermix with the 

 native halophytes. 



Changes in the distribution of 

 individual species within marshes are seen 

 to be common events. Under conditions of 

 local or whole-wetland disturbance from 

 trampling or herbivory to elimination of 

 tidal circulation, individual species may 

 be reduced in area of distribution or 

 eliminated from large patches. Events 

 such as flooding may stimulate widespread 

 expansion, particularly of cordgrass, 

 provided a source of propagules is 

 available. Most of the halophytes do not 

 establish readily from seed; instead, they 

 expand their distributions vegetatively . 

 Only three native annuals, the annual 

 pickleweed ( Salicornia bigelovii ) , the 

 endangered salt marsh bird's beak 

 ( Cordylanthus maritimus ssp. maritimus ) , 

 and the parasitic dodder (Cuscuta salina ) 

 are found; all others are short-lived 

 perennials. Two pickleweeds ( Salicornia 

 virginica and S. bigelovii ) and sea-blite 

 ( Suaeda californica ) appear to be the most 

 opportunistic species. Once established 

 in a newly exposed habitat, Salicornia 

 virginica can probably outcompete other 

 species, especially when soils are 

 hypersaline. Freshwater input stimulates 

 germination of most halophytes and 

 flooding events appear to be important for 

 establishment and expansion of species' 

 distributions. Chance establishment after 

 disturbance is no doubt an important 



factor in understanding the patchy 

 distributions found in many southern 

 California marshes. 



The net annual productivity of the 

 marsh vascular plants (above-ground only) 

 tends to be under 1 kg/m /yr. In 

 comparison with salt marshes of the 

 Atlantic and Gulf of Mexico coasts, where 

 soils are predominantly brackish, the 

 southern California marshes have lower 

 vascular plant productivity. That 

 hypersaline soils are responsible for 

 their relatively low productivity is 

 demonstrated by increases in end-of-season 

 live biomass following reduction of soil 

 salinity by flooding and by higher 

 productivity of marshes with brackish 

 soils. Their relatively short, open 

 canopies are evidence that the vegetation 

 is usually under environmental stress. 

 Both plant density and height increase 

 after flooding. 



43 



