Some of the compositional differences 

 between 1974 and 1984 were probably due to 

 sampling in different locations. The 1974 

 data set included three transects, located at 

 TJE-36, 40, and 43, and the 1984 data set 

 included a larger proportion of samples from 

 cordgrass-dominated areas. The higher 

 frequency of cordgrass in 1984 is a 

 consequence of more intensive sampling, 

 rather than a real increase in the marsh. For 

 these reasons, the 10-year comparison 

 ascribes significance only to large changes in 

 occurrence or cover. If nontidal drought 

 affected the salt marsh, the greatest impact 

 should have been on shallow-rooted species, 

 especially annuals. Species known to have 

 broad ecological tolerance as adults (e.g., the 

 perennial pickleweed and alkali heath, 

 Frankenia grandifolia) should have declined 

 little in response to nontidal drought. 



Most notable in the 10-year comparison 

 are the absences of annual pickleweed 

 (Salicornia bigelovii) and sea-blite (Suaeda 

 esteroa, formerly called S. californica) in the 

 1984 data. Annual pickleweed was a dominant 

 component of the marsh in 1974 (64% 

 frequency), as well as during the 1976 

 productivity study (Chapter 4). During a 

 1975 population study of annual pickleweed, 

 its densities exceeded 4,000/m 2 . In spring 

 1984, the species was observed in seedling 

 stage, although densities were not 

 particularly great. These seedlings did not 

 survive the nontidal spring and summer; no 

 plants were seen in any of the monitored 

 quadrats (n = 215 quadrats) in September 

 1984. Except for a tiny patch located near 

 TJE-28, the population was eliminated at 

 Tijuana Estuary. That small patch has 

 persisted through 1991, and a second sighting 

 occurred near the mouth, which indicates that 

 the species has not been extirpated. Yet its 

 distribution and influence on the marsh are 

 greatly diminished. The decline was 

 restricted to Tijuana Estuary, as annual 

 pickleweed remained abundant at the tidally 

 flushed marsh in Mission Bay, San Diego. 

 Thus, the nontidal period, which coincided 

 with a dry year, was the cause of extreme 



mortality, not only of the seedlings that 

 germinated in early 1984, but also of the seed 

 bank, which has never recovered. 



A second species also declined during 

 1984. The sea-blite is a short-lived 

 perennial that occurred in 37% of the 

 quadrats sampled in 1974 but in only one of 

 those sampled in 1984. Sea-blite was 

 present in the 1976 productivity study and 

 was commonly seen up until 1984. The large 

 change in frequency documents a significant 

 decline, and we attribute it to the nontidal 

 drought. The fact that sea-blite is a short- 

 lived plant without a well-developed root 

 system (Purer 1942) may explain its 

 susceptibility to drought. Likewise, rooting 

 depth and root development limit survival of 

 young seedlings. 



Pickleweed and alkali heath remained 

 abundant through the nontidal period, 

 supporting the hypothesis that perennial 

 species are drought tolerant. Pickleweed was 

 the dominant species throughout the marsh in 

 both 1974 (Zedler 1977) and 1984 (Table 

 5.3). Alkali heath was also very tolerant of 

 the nontidal conditions. Between 80 and 110 

 cm MSL, alkali heath was over 80%-90% 

 frequent in 1974, and it persisted with 

 frequencies of 60%-85% during 1984. 



Compared to the near extinctions of annual 

 pickleweed and sea-blite, the longer-lived 

 species were much less affected by the 

 prolonged period with neither tidal flushing 

 nor rainfall. Mature, long-lived perennials 

 may be able to track a declining water table by 

 extending their roots further into the 

 substrate. Both the perennial pickleweed and 

 alkali heath are frequent and high in biomass 

 at Los Pefiasquitos Lagoon, where tidal 

 flushing has been intermittent over the past 

 several decades (Purer 1942; Bradshaw 

 1968; Carpelan 1969; Zedler et al. 1980). 

 The tolerance of mature perennials to extreme 

 environmental conditions exceeds that of 

 species that rely on seed germination and 

 establishment for persistence. 



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