Table 5.6. Cover (%) of 12 species 

 encountered in the lower-, middle-, and 

 upper-elevation transects. Data are means (4 

 transects x 3 years) for 1989-91, taken in 

 September. 



*=one sighting 



For all three years, cordgrass height 

 distributions (Figure 5.12) showed high 

 proportions of stems in the 61-90 and 91- 

 120 cm height classes. The increased 

 densities in 1990 and 1991 show up as larger 

 proportions of short stems for those two years 

 (Figure 5.12). 



5 . 7 TIJUANA ESTUARY AS A REFERENCE 

 SITE FOR "NATURALLY FUNCTIONING" 

 SALT MARSH 



The existence of a salt marsh monitoring 

 program has significance for two aspects of 

 coastal management. First, as a site that 

 currently supports endangered species, the 

 data from Tijuana Estuary can be used to set 

 goals for resource management and 

 restoration planning. Second, the information 

 can be used as reference data with which to 

 evaluate the functional equivalency of restored 

 or constructed marshes. 



Because Tijuana Estuary has a growing 

 population of clapper rails, it is reasonable to 

 assume that the cordgrass habitat is adequate 

 for rail nesting activities. A comparison of 

 the Tijuana Estuary cordgrass marsh and 

 other marshes that lack clapper rails 

 indicates that cordgrass height distributions, 

 rather than density, biomass, total stem 

 length, or cover data, are a critical attribute 

 of the habitat for nesting and cover (Zedler, in 

 review). In contrast to the height 

 distributions of Figure 5.12, constructed 

 marshes have most of their stems in classes 

 1-2 and few or no stems taller than 90 cm. 

 The problems for clapper rails are obvious 

 when the highest tides occur--this type of 

 cordgrass canopy is completely inundated, 

 while that of the natural marsh protrudes 

 above the water. 



Other species of the cordgrass marsh may 

 also require tall vegetation. The short plants 

 at Chula Vista's Wildlife Reserve (a large 

 dredge-spoil island) have suffered repeated 

 attacks by scale insects (Haliaspis spartina). 

 One natural predator of the scales is a beetle 

 (Coleomegilla fuscilabris; Figure 3.11), 

 which is not an aquatic insect. At high tide, 

 the beetles of the natural marsh can escape 

 inundation by crawling up the tall cordgrass 

 stems (K. Williams, SDSU, pers. comm.). The 

 failure of these beetles to become established 

 on the island may in part be due to its isolated 

 location. However, the failure of beetles to 

 control scales following transplantation to the 

 infested areas by K. Williams is more likely 

 an effect of inadequate cordgrass canopies. 



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