Brief Community Description

Southern coastal salt marsh is a highly productive vegetation community full of herbaceous plants [1]. The majority of plants in this community are suffructescent, especially in the higher drier sites, and salt-tolerant hydrophytes. Vegetation forms moderate to dense cover up to 1 meter tall. Unlike northern coastal salt marsh where species are active in the summer and dormant in the winter, the southern coastal salt marsh has a longer growing season. It intergrades broadly with northern coastal salt marsh along the south central coast. Southern marshes are nowhere as extensive as the larger northern marshes.

Alliances

Species special to the southern coastal salt marsh include Atriplex watsonii, Batis maritima, Lycium californicum, Distichlis littoralis, Suaeda californica, and Arthrocnemum subterminale [2]. Characteristic species include: Amblyopappus pusillus, Atriplex watsonii, Batis maritima, Cressa truxillensis, Cuscuta salina, Distichlis spicata var. spicata, Frankenia grandifolia, Heliotropium curassavicun, Jaumea carnosa, Juncus acutus sphaerocarpus, Limonium californicum, Distichlis littoralis, Salicornia bigelovii, Salicomia spp., Spartina foliosa, and Suaeda californica. Nonnative plants that have invaded southern salt marsh include: Carpobrotus aequilateralis, Mesembryanthemum crystallimum, and M. nodiflorum.

Range wide dist. status

Bays, lagoons, and estuaries along the coast from Point Conception to the Mexican border [1].

MSPA distribution

There are 2,700 acres of salt marsh in the MSPA in MUs 1, 2, 3, 6, and 7, of which 2,296 acres are conserved. There are 1,557 acres in MU1 (1,260 conserved), 15 acres in MU2 (2 acres conserved), 10 acres in MU3 (0.6 conserved), 42 acres in MU6 (39 conserved), and 1,075 acres in MU7 (994 conserved).

Habitat affinities

Salt marsh is typically found along sheltered inland margins of bays, lagoons, and estuaries [1]. The hydric soils found at these sites are subject to regular tidal inundation by salt water for at least part of each year. Water and air temperatures are warmer in southern than northern coastal salt marsh. Frankenia grandifolia, Suaeda califomica, and/or Salicornia subterminalis often occur along the upper, landward edges of the marshes; Salicornia bigelovii, S. virginica, and Batis maritima at middle elevations; and Spartina foliosa closest to open water.

Ecosystem processes

Sites are subject to regular tidal inundation by salt water for at least part of each year [1].

Threats

Since 1850, 75% (5,819 ha) of Southern California salt marshes have been lost [3]. In Los Angeles, Orange, and San Diego County there has been a significant increase in subtidal water while both intertidal and vegetated wetlands have decreased. There are many challenges associated with urban salt marsh restoration, including: habitat isolation and fragmentation, impacts from exotic species, the loss of transitional upland habitats, and alterations to hydrologic and sediment dynamics [4]. The development of salt marsh functions, such as biomass and nitrogen accumulation, slow with low species richness. In many marshes with hydrological modifications nonnative species have invaded the upper reaches of the salt marshes. Some hydrological connections are impaired by roads and structures, constraining the natural migration of channels, and altering sediment dynamics that often lead to lagoon mouth closures. In extreme cases of increased sedimentation, the sediment can cover vegetation and convert salt marsh to upland. The biggest threat to salt marsh are the affects of climate change through accelerated sea-level rise [5, 6], shifting precipitation patterns [7, 8], erosion [9], and changing frequency and intensity of storms [10, 11].

Special considerations

The extensive loss of salt marsh in southern California highlights the need to preserve and restore remaining salt marsh [3]. For habitats that are isolated, planting is vital for ensuring the colonization of dispersal-limited plants [4]. There are additional restoration challenges in areas where the gradual slopes between wetland and upland have been replaced by sharp transitions next to urban developments. This severely limits the ability to restore rare plant and animal populations. Additionally, salt marsh may not be able to move upslope with sea level rise due to surrounding development. There are 15 MSP species associated with salt marsh vegetation.

Sources