Table 4.4. Net aboveground productivity and 

 net carbon (C) productivity (estimated from 

 plant carbon data of 5/31/78) of salt marsh 



vascular plants (data 

 Winfield 1980). 



are per m^/yr from 



Species 



g dry wt 

 •76 '77 



gc 



•76 '77 



40 8 8 



Batis maritima 



saltwort 

 Frankenia grandifolia 



alkali heath 13 3 4 1 



Jaumea carnosa 85 126 23 34 



Limonium californicum 



sea lavender o <1 o o 



Monanthochloe littoralis 



shore grass 21102 8 36 



Salicornia bigelovii 



annual pickleweed 52 145 10 28 

 S. subterminalis 



perennial glasswort 9 14 3 4 

 S. virginica 



pickleweed 1 10 128 2 5 3 



Spartina foliosa 



cordgrass 307 224 98 72 



Suaeda esteroa 



sea-blite 17 53 4 11 



Triglochin concinnum 



arrow grass 1 5 4 



Total 



689 904 191 239 



45% for smooth cordgrass (Mclntire and 

 Dunstan 1976). After correcting the dry- 

 weight data to grams of carbon fixed, Winfield 

 obtained an average marsh productivity of 

 239 g C/m 2 /yr, which was much less than 

 the average given for Georgia (454 g 

 C/m 2 /yr) by Turner (1976). 



However, Onuf's (1987) work at Mugu 

 Lagoon established that harvest methods 

 significantly underestimate productivity of 

 pickleweed, sea lavender, and other southern 

 California salt marsh species (cordgrass was 

 not studied). Much greater production was 



estimated by tagging and remeasuring growth 

 of individual plants. In the case of pickleweed, 

 estimates from monthly harvests totaled half 

 those measured by the tagging method, because 

 so much plant material was broken off and 

 exported between harvests. Succulents are 

 very important in the Tijuana Estuary marsh; 

 thus, it is likely that Winfield's 1976 and 

 1977 data underestimated vascular plant 

 productivity. 



Two considerations discouraged us from 

 repeating the vascular plant productivity 

 studies. First, Onuf's experience convinced us 

 that the work was enormously labor 

 intensive, that funding agencies were unlikely 

 to support further efforts, and that journals 

 were unwilling to publish the detailed 

 demographic analyses required to track 

 branch production, loss, and replacement. 

 Secondly, large changes in biomass followed 

 the 1980 flood and indicated that short-term 

 intensive studies were inappropriate for 

 temporally variable marshes. Alternative 

 approaches were called for, namely, longer- 

 term monitoring of end-of-season biomass 

 (Figure 4.3). 



CM 



E 



in 



03 



E 

 o 



CD 



"O 



c 



en 



> 



s 



1550 



1350 - 



1150 - 



950 - 



750 - 



550 1  1 - i —  1 • r 



1975 1977 1979 1981 1983 



Figure 4.3. End-of-season live biomass of 

 cordgrass plots at Tijuana Estuary (unpubl. 

 data of PERL). Bars are ± standard error; n 

 varied but was always more than 3. 



86 



