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 typically found on alluvial flats, basin floors, valley floors, floodplains, and stream terraces. Slopes typically range from 0 to 9% and elevations vary from sea level to 3000 ft.

Climate

The average annual precipitation covers a diverse landscape in MLRA 19 of valleys and mountains and can range anywhere from 8 to 53 inches (215 to 1,354 millimeters), increasing with elevation. Most of the rainfall occurs as low- or moderate-intensity, Pacific frontal storms during winter. Rain can turn to snow at the higher elevations. A little snow may fall in winter, but it does not last. Summers are dry, but fog provides some moisture along the coast. The average annual temperature is 38 to 67 degrees F (3 to 19 degrees C). The freeze-free period averages 310 days in the valleys, 245 days in the mountains, and ranges from 125 to 365 days along the coast. It decreases in length with elevation. The longest freeze-free period occurs at the lower elevations along the western edge of the area.

Soil features

Soils in this ESG are extremely varied from fine-loamy to sandy, poorly drained to well drained, and water tables are between 30 inches to greater than 72 inches. They are good soils for agriculture and thus many many acres have been converted to irrigated croplands.

Some representative soils include Camarillo, a fine-loamy, mixed, superactive, calcareous, thermic Aquic Xerofluvent; Pacheco, a fine-loamy, mixed, superactive, thermic Fluvaquentic Haploxeroll; Hueneme, coarse-loamy, mixed, superactive, calcareous, thermic Oxyaquic Xerofluvent; and Mocho, a fine-loamy, mixed, superactive, thermic Fluventic Haploxeroll.

Vegetation dynamics

This ESG covers the areas of the valleys in MLRA 19 that were at one time part of a vast complex of marshes, tidal flats, estuaries, wetlands and wet meadows. The urbanized landscape in the valleys within this MLRA that exists today makes it difficult to imagine the natural landscape prior to human development.

These loamy bottoms were likely the loamy-textured depressional and deposition areas and isolated oxbows that were created from the network of freshwater and salt marshes, rivers and streams that ran through these valleys as their seasonal and tidally influenced flood waters stretched across the floodplains and terraces in spring and deposited sediment as they receded during summer. Once the area began to be settled, many of these water dominated ecosystems were drained, leveed, cleared for crops and other agriculture, and urbanized.

As this landscape was de-watered and houses and agriculture took over, the water table for many of these habitats moved deeper and deeper, creating soils that would no longer offer the available soil moisture for many of the plants that had evolved with the hydrologic function of the natural system that no longer existed. These loamy basins may have remained wetter than many of the surrounding soils, due to their prolonged available water capacity and their depressional location on the landscape. The variable range in soil textures will dictate the species composition and production, with the finer soils holding more water that results in more native perennials and forbs and higher annual production overall. The coarser textures will dry out more rapidly through both drainage and evapotranspiration in the summer months making them less hospitable for many of the native perennial grasses and more dominated by annual grasses and forbs. Annual production will still be higher than the other ESGs in bottoms, due to the loamy textures which provide decent available water and slightly slower but still well drained soil conditions.

Historically, this site may have looked similar to the CWHR wet meadow classification, however with the introduction of non-native annual grasses and the impacts from fragmentation, continued de-watering, and human alterations such as homes and roads, this site now reflects a lower producing, dry, annual grassland.

Currently, introduced annual grasses are the dominant plant species in this ESG. These include wild oats, soft chess, ripgut brome, red brome, wild barley, and foxtail fescue. Common forbs include broadleaf filaree, redstem filaree, turkey mullein, true clovers, bur clover, popcorn flower, and many others. Perennial grasses, found in moist, lightly grazed, or relic prairie areas, include purple needlegrass and Idaho fescue. Species composition is also related to water availability with greater amounts of relic perennial grasses in areas of greater precipitation or soil moisture.

Information from:
John G. Kie
California Wildlife Habitat Relationships System
California Department of Fish and Game
California Interagency Wildlife Task Group

Major Land Resource Area

MLRA 019X
Southern California Coastal Plains and Mountains

Subclasses

• R019XD067CA–WET MEADOW 9-20"
• R019XD068CA–SILTY BASIN
• R019XG907CA–Loamy Bottom

Correlated Map Unit Components

23477325, 23477322, 23477311, 23477388, 23477392, 23477475, 23477480, 22665563, 22665239, 23236873, 22665816, 22665827, 22665832, 22665730, 22665728, 22665990, 22665915, 22665916, 22665710, 22666081, 22666003, 22666305, 22666336, 22666510, 22666504, 22666509, 22644229, 22643986, 22669101, 22668579, 22670696, 22670691, 22670695, 22671062, 22671067, 22671423, 22671428, 22671613, 22671259, 22671257, 22670925, 22670919, 22670924, 22671119, 22671376, 22671496, 22671494, 22671495, 22671161, 22671356, 22671221, 22673471, 22673586, 22673585, 22673807, 22673625, 22673386, 22673411, 22673412

Stage

Provisional

Contributors

Curtis Talbot