transects dominated by cordgrass (lower 

 marsh ) n =102 stations monitored since 1979. 



transects dominated by succulents (upper 

 marsh) 1 1 5 stations established in 1984. 



Figure 5.1. Map of lower and upper marsh 

 monitoring transects at Tijuana Estuary. 

 Wide lines = transects dominated by cordgrass 

 ("lower marsh");n = 102 stations monitored 

 since 1979. Thin lines = transects dominated 

 by succulents ("upper marsh"); n = 115 

 stations established in 1984. 



Table 5.1. Elevation (cm above MSL) of 

 quadrats in the 1984 monitoring program. 

 Lower marsh transects are designated 

 cordgrass; upper marsh transects are called 

 noncordgrass. 



5 . 2 PHYSICAL CHANGES FOLLOWING 



ECOSYSTEM-WIDE DISTURBANCES 



5.2.1 Soil Salinity Changes 



Interstitial soil salinities, measured 

 annually in September, indicate that the lower 

 marsh is usually hypersaline, i.e., more 

 saline than sea water (Figure 5.2). Additional 

 data from April of each year help to show the 

 effect of winter rainfall, although the salinity 

 minimum may not always be depicted by the 

 April sampling date. Long-term records show 

 the following: 



• Soil salinity dropped to 15 ppt in April 

 1980, after major flooding in both January 

 and February. The minimum soil salinity may 

 have been lower and earlier than measured. 



1 00 



