. The ecology of Tijuana Estuary, California : a national estuarine research reserve . -i—i—i—i—i—i—i—|—i—|— 1978 1980 1982 1984 1986 1988 Figure Frequency of occurrence of cordgrass (Spartina foliosa) and pickleweed (Salicornia virginica) in original low-marsh sampling stations (n = 102) from 1979 through 1988. Data are from September of each year. The estuary was nontidal for 8 months during 1984. plants that still had some green leaf material were clearly dead, and the annual census showed minimum occurrences. The widespread pattern of mortality was unprecedented in our data base, and
. The ecology of Tijuana Estuary, California : a national estuarine research reserve . -i—i—i—i—i—i—i—|—i—|— 1978 1980 1982 1984 1986 1988 Figure Frequency of occurrence of cordgrass (Spartina foliosa) and pickleweed (Salicornia virginica) in original low-marsh sampling stations (n = 102) from 1979 through 1988. Data are from September of each year. The estuary was nontidal for 8 months during 1984. plants that still had some green leaf material were clearly dead, and the annual census showed minimum occurrences. The widespread pattern of mortality was unprecedented in our data base, and there is every reason to conclude that it was caused by drought and hypersalinity. Recovery of the cordgrass did not immediately follow the restoration of tidal flows, which was completed in December of 1984. After four years, the species had not quite regained its average frequency before closure. Pickleweed (Salicornia virginica) was the second most abundant species in the lower marsh, but its occurrence changed little from 1979-1984 (Figure ). After closure, however, there was a gradual increase in the distribution of the species. The habitat changed in ways that were not documented; this expansion is not explained by soil salinity. Perhaps the one-time reduction in waterlogging during 1984 removed barriers to establishment, and once mature plants were present, they were able to persist. Species interactions may explain some of the patterns of occurrence for cordgrass and pickleweed, although data other than occurrence are needed to test their potential interactions. Biomass data are useful measures of plant abundance, but sampling for biomass is very destructive, especially at permanent monitoring stations. Instead, we use surrogates of biomass. Cordgrass is sampled as the total stem length (sum of all plants heights in a quadrat). The correlation between cordgrass TSL and dry weight is significant for September data at Tijuana Estuary (r = , n =
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