The ecology of Tijuana Estuary, California : a national estuarine research reserve ecologyoftijuana00zedl Year: 1992 Live Weight Standing Dead Weight I MAMJJASONDJ FMAMJJ ASONDJFMAMJJ ASON ' 1976 1 1977— —' 1978 ' Figure Live biomass and dead standing crop for salt marsh vascular plants. Vertical bars are ±_1 standard error, n = 25. Reprinted from Winfield (1980) with permission. Species-specific differences in standing crop are easiest to see in the 1977 harvest data, for which the number of sampling stations was constant. The annual pickleweed (Salicornia bigelovii) had the largest
The ecology of Tijuana Estuary, California : a national estuarine research reserve ecologyoftijuana00zedl Year: 1992 Live Weight Standing Dead Weight I MAMJJASONDJ FMAMJJ ASONDJFMAMJJ ASON ' 1976 1 1977— —' 1978 ' Figure Live biomass and dead standing crop for salt marsh vascular plants. Vertical bars are ±_1 standard error, n = 25. Reprinted from Winfield (1980) with permission. Species-specific differences in standing crop are easiest to see in the 1977 harvest data, for which the number of sampling stations was constant. The annual pickleweed (Salicornia bigelovii) had the largest temporal increase (), while shore grass had the least (). Year-to-year differences in August biomass were also large. Variability, then, is the rule; it is high from species to species, season to season, and year to year. Onuf (1987) reached the same conclusion in his analysis of pickleweed biomass at Mugu Lagoon. NUTRIENT INTERACTIONS Our understanding of the nutrient cycles at Tijuana Estuary is limited. Most of the work has focused on nitrogen, because nitrogen has long been accepted as the major limiting factor in coastal ecosystems. Smith (1984) has challenged that dogma and claimed that phosphorus is likely to limit estuarine systems, even though small-scale experiments might indicate that nitrogen controls plankton growth. Howarth and Cole (1985) support the theory of nitrogen limitation and provide a convincing argument that anaerobic conditions favor nitrogen limitation. Winfield (1980) studied nitrogen dynamics in detail and determined that there is a net flux of inorganic nitrogen from the tide waters to the marsh. His estimate of the amount of nitrogen imported by the marsh ( g N/m2/yr) was far less than the total required for above-ground plant growth (only 28), and even a smaller portion of the nitrogen required for vascular-plant and algal productivity combined (6). While these calculations do not rule out phosphorus or other nutrient
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