Gosselink 1976, and Hopkinson et al. 

 1978). 



Productivity studies have been 

 carried out in several of the southern 

 California wetlands (Table 7). All 

 investigators calculate increases in 

 biomass between periodic harvests of the 

 vegetation, a technique which does not 

 account for biomass lost to herbivores, 

 decomposers or export from the marsh. 

 Chris Onuf (unpub. ms) has also employed a 

 plant tagging technique, which is perhaps 

 the best means of estimating losses of 

 plant biomass between harvests. According 

 to his comparisons of harvest and tagging 

 methods at Mugu Lagoon (Onuf et al. 1978), 

 the harvest method underestimates 

 productivity by a factor of 2.1 to 2.2 for 

 pickleweed ( Salicornia virginica ), 3.7 for 

 Jaumea carnosa , 1.8 for sea lavender 

 ( Limonium californicum ) , and 2.9 for 

 saltwort ( Batis maritima ) . It is not 

 surprising that losses are high for the 

 brittle-stemmed pickleweed; its branches 

 are readily snapped off in trampling 

 (Mclntyre 1977) and presumably also by 

 wildlife and tidal currents. Errors in 

 harvest-derived productivity data clearly 

 vary with the marsh species composition. 

 Yet these are the most widely available 

 data. For purposes of comparing marsh 

 productivity from one marsh to another and 

 one region to another, estimates based on 

 periodic harvests must be relied upon. 



Tijuana Estuary (Zedler et al. 1980, 

 Winfield 1980) and Mugu Lagoon (Onuf et 

 al. 1978) have net above-ground 

 productivities of up to 1 kg/m per year. 

 The higher values tend to coincide with 

 cordgrass's dominance. These values are 

 probably representative of less disturbed, 

 seasonally hypersaline marshes in southern 

 California and they fall well below 

 estimates for Atlantic and Gulf of Mexico 

 marshes dominated by smooth cordgrass 

 ( Spartina alterniflora ) . 



Eilers (1981) presents productivity 

 data for two additional hypersaline 

 marshes in southern California, the 

 Sweetwater River marsh within San Diego 

 Bay and Upper Newport Bay marsh. However, 



by calculating productivity on the basis 

 of individual sampling stations (with one 

 quadrat per sample date), he produces 

 averages which are biased upward due to 

 spatial variability (see Turner's [1976] 

 discussion of error accumulation using the 

 Smalley calculations). Re-analysis of 

 Eilers' data, averaging biomass over all 

 quadrats sampled at each date, gives 

 results which are more in line vd.th those 

 of other studies (1.1 kg/m /yr for 

 Sweetwater River marsh and 0.7 for Upper 

 Newport Bay marsh) . 



High soil salinity is probably the 

 major limiting factor for vascular plant 

 growth in southern California. Laboratory 

 studies of Pacific Coast species (Barbour 

 1970, 1978; Barbour and Davis 1970; 

 Phleger 1971) support the conclusion that 

 fresh water enhances halophyte growth. 

 Field experiments to vary soil salinity 

 are less easily performed, and it becomes 

 necessary to compare events associated 

 with hypersaline and brackish conditions. 



2.8 PRODUCTIVITY FOLLOWING FRESHWATER 

 INPUT 



Since flooding substantially reduced 

 the soil salinity at Tijuana Estuary in 

 spring 1980, one would predict an increase 

 during that growing season. Although 

 the monitoring of productivity has not 

 continued, measurements of standing crop 

 are made at the end of each growing 

 season. The average live biomass in 

 August correlates well with annual 

 productivity (r=0.9, n=11 southern 

 California marsh study sites), so that 

 responses to changing soil salinity can be 

 crudely measured by one harvest period. 



The lower marsh vegetation at Tijuana 

 Estuary had August standing crops of 0.9 

 to 1.1 kg/m (live only) in years prior to 

 the 1980 floods (Zedler et al. 1980). 

 After the January-February floods and the 

 brief period of brackish soils, the August 

 1980 standing crop was 1.4 kg^m . 

 However, it dropped back to 1.1 kg/m in 

 1981, when soils were hypersaline all 

 year. Higher productivity in 1980 

 resulted from increases in both the 



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