| Halophyte responses to soil variation and interspecific competition were studied in four Southern California marshes. In a constructed marsh in Mission Bay, experiments were conducted to test whether establishment of planted Spartina foliosa depended on transplant source, soil texture, soil organic matter, or organic soil amendments: alfalfa, kelp, peat, and processed sewage. Short transplants from the adjacent natural marsh exhibited greater initial survival and growth than more robust transplants from other Mission Bay donor marshes but “Donor effects” did not persist beyond three months. S. foliosa grew best on relatively fine-grained, organic-rich soils (>14% mud and >5% organic content). Of all organic fertilizers tested, only processed sewage enhanced Spartina foliosa growth.; Salicornia bigelovii rapidly colonized fertilized and unfertilized areas. S. bigelovii in sewage-treated soil was taller and produced more seeds than in peat- or kelp-treated soil. The tallest seed-bearing individuals were found in fine-grained (mud >14%), organic-rich (organic content >5%) soil.; Experiments in the Northern Wildlife Preserve (Mission Bay) tested effects of freshwater and nitrogen addition on Spartina foliosa grown with or without its potential competitor, Salicornia virginica. Nitrogen increased growth of both species, suggesting that plants in this marsh are nitrogen limited. Freshwater application increased herbivory on S. foliosa. Substitutive and additive experiments did not reveal competitive interactions between S. virginica and Spartina foliosa.; Relationships between marsh vegetation and soils were compared in four marshes. Soil and assemblage composition, relationships between plant and soil variables, and S. virginica morphology varied significantly among the Mission Bay constructed marsh, Northern Wildlife Preserve, Tijuana River National Estuarine Research Reserve, and Upper Newport Bay marshes. The constructed marsh was the most distinct in many respects, however its assemblages were similar to those of the adjacent Northern Wildlife Preserve.; Compared to east-coast counterparts, southern California marshes are discontinuous and isolated, and their halophytes seem highly adapted to local conditions. Halophyte responses to physical factors are marsh-dependent in nature and intensity, making extrapolations across marsh systems difficult. Each southern California marsh must be viewed as a unique entity and managed accordingly. |
