Nitrogen Assessments in a Constructed and a Natural Salt Marsh of San Diego Bay

Abstract

Soil nitrogen pools were lower in a 4-yr-old constructed salt marsh than in an adjacent natural marsh of San Diego Bay. Aboveground biomass and foliar nitrogen content of Spartina foliosa were both lower for the constructed marsh. Soil organic carbon, which was highly positively correlated with total nitrogen, was also lower in the constructed marsh. Rates of nitrogen fixation were higher for the natural marsh in surface soils (1 cm depth) but not in the rhizosphere (10 cm depth). Experimental additions of organic matter increased rates of nitrogen fixation substantially for both the constructed and natural marsh soils, with glucose stimulating greater increases than Spartina foliosa detritus (roots and rhizomes). In comparison with natural marshes studied elsewhere, the San Diego Bay sites have low nitrogen pools and little soil organic carbon. Nitrogen mineralization rates (in situ incubations) were high in both marshes studied. The low nitrogen pools reflect low tidal import and infrequent streamflow influxes and, possibly, high nitrogen demands of vegetation stressed by hypersaline soils.

The Pace of Ecosystem Development of Constructed Spartina Alterniflora Marshes

“…east coast marshes revealed that c.onstructed (192 gesting that decomposition is not restricted by a threshglm2) and natural (453 glm2) marshes in southern Cal-old C concentration. Soil N is important because it ifornia contained less Spartina biomass than marshes represents ecosystem N capital, but, because most soil in North Carolina (constructed marsh = 713 g/m2, nat-N is bound in organic C compounds in fairly fixed ural marsh = 992 g/m2) (Langis et al 1991, Craft et ratios, its abundance usually tracks that of organic C. al.…”

“…In this study, our 3-yr-old constructed marsh contained three times more biomass (671 glm2) than a Surprisingly, N was not correlated with measures of 4-yr-old S. foliosa marsh in southern California (192 Spartina aboveground production (Table 4). Both C and glm2) (Langis et al 1991). N were predictable, relatively easy to use and inexHuman alteration of the surrounding landscape and pensive (Table 3).…”

“…Also, the amount of Spartina biomass produced in southern California marshes is less a s compared to marshes o f the southeastern U.S. (Langis et al 1991, Craft et al 1999 Attributes linked t o heterotrophic processes tracked the development o f soil organic C pools and gradually increased t o convergence over time. Primary producers (Spartina, epiphytic algae) and heterotrophic activity (decomposition, benthic invertebrates) converged to equivalence within 5-15 years following marsh construction.…”

Changes in the Food Web Linked to Restoration Effort Intensity and Watershed Conditions

“…Dredge spoil soils vary in texture, but many used for marsh creation have tended to be very sandy [33] [34]. Several studies have found that soils of dredge spoil marshes have higher sand, less clay, and less organic matter, including MOM, than adjacent natural marshes [10] [12] [35] [36].…”

The biospheric life support system: a unifying concept for ecotoxicologists and ecologists

“…Research from Zedler and her colleagues, which examines both structure and function of constructed salt marshes in Southern California, illustrates how complex these relationships are and the importance of monitoring a range of parameters to understand them (Langis et al, 1991;Zedler, 1993;Boyer and Zedler, 1998). …”