CHAPTER 2 

 VASCULAR PLANT VEGETATION 



Given the relatively short list of 

 species known to tolerate saline 

 conditions worldwide and realizing that 

 even these species grow best in 

 environments less saline than the 

 intertidal zone, one might predict a 

 rather limited flora and highly stressed 

 community for hypersaline marshes. This 

 appears to be the case. Up to 17 

 halophytes (mostly succulents) are common 

 in the areas of greatest tidal influence 

 (Table 4). They intermix to produce a 

 low-growing, relatively open canopy of 

 vegetation which readily responds to 

 decreased salinities by becoming taller 

 and more dense. 



Despite the short list of species 

 found in southern California marshes, 

 there is wide variation in vegetation 

 structure and functioning from marsh to 

 marsh, as well as within individual 

 wetlands. At the smaller scale, 

 compositional differences relate to 

 position over the intertidal elevational 

 range and to patterns of establishment, 

 followed by vegetative expansion. At a 

 larger scale, many of the structural 

 patterns relate to the size of the wetland 

 and its history of tidal circulation and 

 other disturbances. Functional patterns, 

 especially differences in primary 

 productivity, show strong correlations 

 with soil salinities. Plant growth 

 differs both spatially and from year to 

 year, increasing in areas of brackish 

 soils and during years of heavy rainfall. 



This description of marsh vegetation 

 begins with the patterns of composition 

 which occur from low to high intertidal 

 position. Factors controlling the 

 distribution of the more common halophytes 

 are discussed, and changes in species 

 composition following various types of 

 disturbances are documented. Together, 

 the observations of spatial and temporal 

 patterns of composition suggest a 



conceptual model of marsh community 

 development. Plant productivity data are 

 summarized and the relationships between 

 plant growth and freshwater influence are 

 demonstrated. 



Although a thorough understanding of 

 what controls marsh structure and 

 functioning awaits experimental tests of 

 the ideas put forth here, we can conclude 

 with certainty that southern California 

 marshses are highly dynamic communities 

 which readily respond to both natural and 

 man-caused environmental changes. 



2.1 COMPOSITION AND INTERTIDAL POSITION 



While this profile of marsh structure 

 does not include all of the variation 

 within southern California, it summarizes 

 present knowledge, indicates what 

 ecologists have determined to be the most 

 likely characterization of undisturbed 

 marsh vegetation, and provides a model for 

 restoration and enhancement of degraded 

 systems . 



Distributional changes of species 

 with elevation can be described at the 

 small-scale or individual-marsh level. 

 Because most of the halophytes rely on 

 vegetative reproduction (rather than 

 seedling establishment) for areal spread, 

 discrete patches and boundaries can be 

 seen in the marsh. In fact, patches seem 

 to be the rule rather than the exception, 

 suggesting that species distributions are 

 commonly in a state of change. Also, 

 since heights of a few species, such as 

 cordgrass ( Spartina foliosa ) and spiny 

 rush ( Juncus acutus ), greatly exceed those 

 of the low-growing succulents, a marsh may 

 display discrete boundaries where the 

 upper or lower limits of such species 

 occur. However, averaging occurrences or 

 cover values over the full elevational 

 range of a marsh shows that (1) most 



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