Tidally-Influenced, Freshwater

Description

The species composition of the two community phases of the reference state are poorly documented in relation to the site and are better understood at the scale of the land resource unit (LRU) as a diverse mosaic of both marsh and riparian forest vegetation types. Through the influence of both tidal and riverine hydrology, these soils represent both the immediate depositional zone of upstream sediments as well the plant communities most likely to be controlled by high water table influences.

This reference state consists two community phases, 1.1 which represents a recently disturbed, inundated and/or deposited soil dominated by pioneering emergent wetland vegetation, and community phase 1.2 representing a less recently disturbed and more diverse mosaic of herbaceous wetland communities. Not surprisingly, this vegetation of community phase 1.2 represents the continuous accumulation of organic material in the soil from onsite vegetation contributions leading to the histosol classification of the representative soils.

While most of the LRU has been subjected to significant hydrologic alteration, echoes of these two community phases remain observable in areas which were deemed too economically difficult to reclaim for agricultural purposes or where such efforts to reclaim the land failed and the preexisting hydrology exerted itself.

Submodel

Description

This state represents a partially controlled hydrology with notably drier soil conditions than historic conditions afforded by the application of levees and in some cases dewatering by pumping or marginally effective gravity drainage. It generally occurs side-by-side with State 3 in the form of fringe areas or blocks between actively cultivated fields or restored areas approaching some semblance of the reference state. The condition of these areas include some retention of natural topography and native vegetation.

This is the most likely state that the ecological site could be restored to as has been pursued in areas such as Twitchell Island.

There is potential in any State 2 community phase to restore conditions to the Reference State by removing artificial barriers to hydrology and other more superficial dewatering efforts. Due to the complexity of water flow regulation within the LRU, areas of approximate historic elevation and proximity to natural water flows present the highest opportunity for successful restoration to the Reference State. Restoration of this state in some cases presents unique complications for adjacent land management objectives which may be influenced by altered hydrology.

Submodel

Description

This is the representative state with over 90% of the ecological site in agriculture production. Based on ground and surface water management and other agronomic inputs, this state is considered to produce the most biomass of any of the three states.

This state represents the highest degree of alteration of the ecological site primarily through hydrologic alteration in the form of diversions and successful conversion to agricultural production. As a result of the historic reclamation practice of installing levees and the burning of the organic soil surface coupled with cultivation effects on carbon mineralization of organic accumulations, some of the histic soils have lost enough diagnostic organic matter content and subsequently have been classified as mollisols.

Restoration of the ecological site when in State 3 is substantially more complex, primarily due to the agricultural resources at stake. Typically held as some of the most productive land in California, restoration efforts within State 3 require very careful planning especially where land ownership is complex. Additionally, some island areas of this ecological site have elevations significantly lower than flanking waterbodies and in such cases, the possibility of an open body of water occurring where the island exists is of substantial concern in some cases.

Submodel