Ecological site group description

Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.

Physiography

This ESG is found on tidal flats near the coastline, with slopes from 0-1% and elevations at -10 ft below sea level to approximately 30 ft.

Climate

The average annual precipitation in this area is 11 to 53 inches (272 to 1,353 millimeters). The higher amounts of precipitation occur at the higher elevations in the area north of San Francisco. Most of the rainfall occurs as low- or moderate-intensity, Pacific frontal storms during winter. This area is very dry from midspring to midautumn. Snowfall is rare. The average annual temperature is 54 to 61 degrees F (12 to 16 degrees C). The freeze-free period averages 315 days and ranges from 265 to 365 days. It is longest near the coast, and it becomes shorter with elevation.

Soil features

Soils for these tidal flats are variable, but all will be saline and wet, with a water table at or near the surface most of the year. They are poorly drained soils that experience frequent flooding and vary between frequently ponded to no ponding. The soils textures and pH will vary depending on parent material and source waters with most being alkaline, and others being acidic.

Representative soils may include Reyes, Novato, Alviso and Coquille

Vegetation dynamics

This tidal salt flats ESG represent the myriad of seasonal wetlands that are characteristic of the Mediterranean climate coastal environment of MLRA 14 in Northern California. They are subject to intermittent flooding due to tidal or freshwater influence and remain unvegetated due to salt concentration, with soil salinities often exceeding 100-200 ppt. They are extremely dynamic features, experiencing large fluctuations in salinity and inundation. They were widespread historically and are present in many Southern California estuaries today, providing an array of ecosystem functions for resident and migratory wildlife. However, due to the extent of urbanization in this ESG, many of these tidal flats no longer exist and have become fragmented and significantly altered. Little is known about their formative processes, historical and contemporary distribution, and ecosystem functions and services of salt flats in the region relative to other estuarine habitat types.

These tidal salt flats indicate some degree of disconnectivity from regular tidal inundation that would allow for desiccation, either due to elevation (e.g., above Mean Higher High Water where inundation is infrequent) or a physical barrier such as sand dunes or inlet closure. As a result, salt flat conditions and dynamics (including shape and landscape position, inundation regime, soil and water salinity, sediment dynamics) are variable from year to year and feature to feature.

Major Land Resource Area

MLRA 014X
Central California Coastal Valleys

Stage

Provisional