Natural Resources
Conservation Service
Ecological site R151XY677TX
Saline Fluid Marsh
42+ PZ
Last updated: 3/24/2025
Accessed: 08/17/2026
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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.
MLRA notes
Major Land Resource Area (MLRA): 151X–Gulf Coast Marsh
Major land resource area (MLRA)151, Gulf Coast Marsh, is in Louisiana (95 percent), Texas (4 percent), and Mississippi (1 percent). It makes up about 8,495 square miles (22,015 square kilometers). The towns of Gretna, Chalmette, and Marrero, Louisiana, and the city of New Orleans, Louisiana, are in the eastern part of this MLRA. The town of Port Arthur, Texas, is in the western part. Interstate 10 and U.S. Highway 90 cross the area. The New Orleans Naval Air Station is in this MLRA. Fort Jackson, overlooking the mouth of the Mississippi River, and the Jean Lafitte National Historic Park and Preserve are in the MLRA. A number of national wildlife refuges and State parks occur throughout this area. MLRA 151 is a very complex ecosystem with active deltaic development and subsidence with extreme anthropogenic impact by man with construction of flood protection levees and channelization occurring on the eastern portion of the MLRA. The Western portion of the MLRA is more stable in that portions of the landscape is protected naturally by the Chenier's, although there is Anthropogenic affects of the interior due to channelization for navigation.
Classification relationships
Major Land Resource Area (MLRA) and Land Resource Unit (LRU) (USDA-Natural Resources Conservation Service, 2006)
Ecological site concept
This plant community is dominated by smooth cordgrass which is specifically adapted to this site. Average depth of water at high tide ranges from 2 to 12 inches and water salinity varies from 12 to 50 ppt, but may become fresher during periods of high rainfall. Increaser plants are seashore saltgrass, glassworts, maritime saltwort, and saltmarsh bulrush. Widgeongrass may occupy some of the open water adjacent to the tidal flat.
Associated sites
R151XY673TX INTERMEDIATE Firm MARSH
R151XY676TX INTERMEDIATE Fluid MARSH
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Avicennia germinans
Herbaceous (1) Spartina alterniflora
(2) Distichlis spicataPhysiographic features
This site occurs adjacent to saline bays and bayous in areas subject to direct tidal inundation. The site is a broad, nearly level, coastal flat.
Table 2. Representative physiographic features
Landforms (1) Salt marsh
(2) Tidal flat
(3) Estuary
Flooding duration Very long (more than 30 days) Flooding frequency Very frequent Ponding duration Very long (more than 30 days) Ponding frequency Frequent Elevation 0 – 1 ft Slope 0 % Ponding depth 1 – 12 in Water table depth 0 – 6 in Aspect Aspect is not a significant factor Climatic features
The following climatic data is from the weather station listed below. Site specific weather data should be used for land management decision making. For site specific weather conditions, obtain data from a weather station close to the site.
Winds effect surface water levels on this site. Southerly winds tend to elevate tides and prevent fresh water run off. Northerly winds lower tides in the Gulf of America and allow water to escape from shallow marshes and bays. Strong cold fronts periodically deplete all surface water until the winds subside and incoming tides return.
Severe tropical storms occur about once every 10 years and lesser strength storms once every five years. The main tropical storm months are August and September but a storm may occur as late as October.Table 3 Representative climatic features
Frost-free period (average) 350 days Freeze-free period (average) 300 days Precipitation total (average) 60 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
Figure 3. Annual precipitation pattern
Figure 4 Annual average temperature pattern
">Influencing water features
This site is subject to direct tidal inundation. The site is continuously saturated with saline water that varies from 12 to 50 parts per thousand but may become fresher during periods of high rainfall. The average water depth at high tide is two to twelve inches. During low tides, all but one or two inches will drain off.
Soil features
The only soil series in this site is Scatlake. It is a saline, loamy to clayey light gray to dark gray, moderately acid to moderately alkaline soil. It is very deep, very poorly drained, very slowly permeable fluid mineral soil. Surface runoff and internal drainage are lacking. The soil is permanently saturated to the surface. The soil is too soft to support the weight of livestock.
Table 4. Representative soil features
Surface texture (1) Mucky clay loam
Family particle size (1) Clayey
Drainage class Poorly drained Permeability class Very slow Soil depth 80 in Surface fragment cover <=3" Not specified Surface fragment cover >3" Not specified Available water capacity
(0-40in)4 in Electrical conductivity
(0-40in)8 – 16 mmhos/cm Sodium adsorption ratio
(0-40in)9 – 18 Soil reaction (1:1 water)
(0-40in)5.6 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)Not specified Subsurface fragment volume >3"
(Depth not specified)Not specified Ecological dynamics
This is a permanently saturated or flooded wetland site that occurs along the immediate upper Texas coastline as a broad, nearly level, coastal flat. The vegetation of the site is entirely influenced by elevation, daily tidal inundation, and salinity levels. Natural shallow drains and ponds are interspersed throughout the site.
Subsidence, a drop in land elevation, may cause a transitional shift from a marsh plant community to a deep open water state. Subsidence may occur naturally or be influenced by human activities such as pumping from wells or the creation of navigation channels. As subsidence progresses, vegetation is submerged and may weaken and die. Loss of anchoring vegetation and subsequent subaqueous erosion of surface sediment and organic detritus through current or wave action moves the site to a deep open water state. Transition back to the fluid saline marsh state will only occur when elevations are restored by filling and the smooth cordgrass community has been re-established by planting and subsidence mechanisms have been removed.
Prescribed fire is not a tool used to maintain this site. Fires occuring when the marsh is dry may remove the organic matter that anchors the herbaceous plant community and allow currents, tides, or wave action to sweep surface sediments and plants away resulting in a deep open water state.
Grazing has no influence on the site as the soils are too soft to support the weight of domestic livestock.
State and transition model
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Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 2 submodel, plant communities
State 1
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant Community
Figure 5. Smooth Cordgrass Plant Community
This historic climax plant community is virtually a monoculture of smooth cordgrass (Spartina alterniflora). Other species that occur in small amounts include seashore saltgrass (Distichlis spicata), marshhay cordgrass (Spartina patens),needlegrass rush (Juncus roemarianus), maritime saltwort (Batis maritimus), Dwarf glasswort (Salicornia bigilovii), Virginia glasswort (Salicornia virginica),Saltmarsh bulrush (Schenoplectus robustus),Perennial saltmarsh aster (Symphyotrichum tenuifolium), Bushy sea-oxeye (Borrichia frutescens), and Black mangrove (Avicennia germinans).
A transition away from the smooth cordgrass dominant community to deep open water occurs when subsidence or fire allows waves or tides to remove the organic substrate that anchors the herbaceous plant community in place.Figure 6. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
Plant type Low
(lb/acre)Representative value
(lb/acre)High
(lb/acre)Grass/Grasslike 8550 9975 11400 Forb 450 525 600 Shrub/Vine 0 0 0 Total 9000 10500 12000 Table 6. Ground cover
Tree foliar cover 0% Shrub/vine/liana foliar cover 0-10% Grass/grasslike foliar cover 70-90% Forb foliar cover 0-10% Non-vascular plants 0% Biological crusts 0% Litter 10-30% Surface fragments >0.25" and <=3" 0% Surface fragments >3" 0% Bedrock 0% Water 10-30% Bare ground 0% Table 7. Soil surface cover
Tree basal cover 0% Shrub/vine/liana basal cover 0-10% Grass/grasslike basal cover 40-60% Forb basal cover 0-10% Non-vascular plants 0% Biological crusts 0% Litter 40-60% Surface fragments >0.25" and <=3" 0% Surface fragments >3" 0% Bedrock 0% Water 40-60% Bare ground 0% Table 8. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – – – – >0.5 <= 1 – – – – >1 <= 2 – – 0-10% 0-10% >2 <= 4.5 – – 70-90% – >4.5 <= 13 – 0-1% – – >13 <= 40 – – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – Figure 7. Plant community growth curve (percent production by month). TX8001 , Fluid Saline Marsh. Smooth cordgrass, warm season perennial, 365 day growing season, permanently flooded or saturated site..
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec J F M A M J J A S O N D 1 5 15 20 20 10 10 5 5 5 3 1 State 2
Open WaterMarsh plants exist in a delicate balance with water depth and salinity levels. When this balance is altered, the plant community adapts to the new regime. The Open Water community is where the system is breaking up or where open water ponds exist within the landscape. This phase requires knowledge of the landscape to determine whether it is breaking up. The open water areas within a planning unit are beneficial for wildlife, but require monitoring to insure that they are not enlarging due to erosion of the shorelines which can be a symptom of a marsh unit that it deteriorating.
Community 2.1
Open WaterTransition 1
State 1 to 2Subsidence
Restoration pathway 1
State 2 to 1Fill and or Plant site
Additional community tables
Table 9. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 7700–10300 smooth cordgrass SPAL Spartina alterniflora 7700–10300 – 2 430–570 saltgrass DISP Distichlis spicata 430–570 – saltmeadow cordgrass SPPA Spartina patens 430–570 – 3 430–570 needlegrass rush JURO Juncus roemerianus 430–570 – Forb4 350–900 turtleweed BAMA5 Batis maritima 350–900 – dwarf saltwort SABI Salicornia bigelovii 350–900 – perennial saltmarsh aster SYTE6 Symphyotrichum tenuifolium 350–900 – Shrub/Vine5 0 black mangrove AVGE Avicennia germinans 0 – Table 10. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
This site provides habitat for a great variety and quantity of birds, animals, and marine life. Research indicates that up to 16,000 pounds of detritus per acre has been produced on this site. Detritus is the beginning of the entire marine ecosystem. Oysters, crabs, and many species of fish depend on this site to supply nutrients. Post-larval shrimp must have smooth cordgrass as a nursery ground during their life cycle.
Hydrological functions
This site is at or slightly above sea level and is flooded by tides daily. The water table is at or above the ground year round. Surface runoff and internal drainage are lacking. The average depth of water at high tide is 2 to 12 inches. During low tides, all but one or two inches will drain off. Tide flood water associated with tropical storms may be four or more feet deep for short periods.
Recreational uses
Fishing, crabbing, hunting, bird watching.
Wood products
None
Supporting information
Type locality
Location 1: Jefferson County, TX UTM zone N UTM northing 29.6884 UTM easting 93.84542 Latitude 29° 41′ 18″ Longitude 93° 50′ 43″ General legal description Texas Point NWR Other references
NRCS Soil Survey for Jefferson and Orange Counties.
NRCS NASIS soils database.
USDA Plants database.
Tidal Flat Range Site Description (TX).
Saline Mineral Marsh Range Site Description (LA).
Shallow Stratigraphic Evidence of Subsidence
and Faulting Induced by Hydrocarbon
Production in Coastal Southeast Texas.
Morton, R.A., Purcell, N.A.,Peterson, R.L.
USGS Open File Report 01-274.
Aquatic and Wetland Plants of the Western Gulf
Coast. Stutzenbaker, C.D., Texas Parks and
Wildlife Press. 1999.
Contributors
Mike Stellbauer, Zone RMS, NRCS, Bryan, Texas
Approval
Matthew Duvall, 3/24/2025
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
Author(s)/participant(s) Mike Stellbauer Contact for lead author Mike Stellbauer, Zone RMS, NRCS, Bryan, Texas Date 09/23/2005 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
None -
Presence of water flow patterns:
None -
Number and height of erosional pedestals or terracettes:
None -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
None -
Number of gullies and erosion associated with gullies:
None -
Extent of wind scoured, blowouts and/or depositional areas:
None -
Amount of litter movement (describe size and distance expected to travel):
None noticeable. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface is resistant to erosion. Stability class range is expected to be 5-6. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Soil surface structure is about 6 inches thick very dark gray organic layer over dark gray fluid mucky clay. SOM is 2-25%. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
This tallgrass marsh site with adequate cover and little bare ground provides for maximum infiltration and little runoff under normal rainfall events. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
None -
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Warm-season tallgrasses/grass-likes >>Sub-dominant:
Cool-season grasses/grass-likes >Other:
Warm-season forbsAdditional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Decadence of warm-season tallgrasses/grass-likes is normal and contributes to the high percentage of organic matter that characterizes this site. -
Average percent litter cover (%) and depth ( in):
-
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
9000# for below average moisture years to 12000# for above average moisture years. -
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
None -
Perennial plant reproductive capability:
All perennial plants should be capable of reproducing
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