Texas Coast Dune Grassland
Summary
This ecological system consists of wetland and upland herbaceous and shrubland vegetation of barrier islands, near-coastal areas, and the Coastal Sand Plain along the Texas coast in the northern Gulf of Mexico. Plant communities of primary and secondary dunes, interdunal swales, barrier flats, and adjacent mainland are included. Salt spray, saltwater overwash, and sand movement are important ecological forces. Some examples of this system naturally occurred as an open matrix of midgrass species within native mesquite - acacia shrublands dominated by Prosopis glandulosa, Acacia farnesiana, and Acacia rigidula but have become shrub-dominated due to the lack of fire.
Source: NatureServe Explorer
Vegetation
This system includes upland, grass-dominated vegetation on deep sands. Dunes are often dominated by Uniola paniculata, with other species such as Croton punctatus, Panicum amarum, Ipomoea pes-caprae, Ipomoea imperati, Tidestromia lanuginosa, Cakile spp., and Sesuvium portulacastrum also present. Upland grasslands are often dominated by Schizachyrium littorale and Paspalum monostachyum. Numerous other species, such as Sorghastrum nutans, Paspalum plicatulum, Muhlenbergia capillaris, Cenchrus spinifex, Elionurus tripsacoides, Eragrostis secundiflora, Bothriochloa laguroides ssp. torreyana, Heteropogon contortus, Andropogon glomeratus, Spartina patens, and Dichanthelium spp., may also be common. Numerous forbs, including such species as Heterotheca subaxillaris, Croton spp., Chamaecrista fasciculata, Rayjacksonia phyllocephala, Physalis spp., Helianthus argophyllus, Gaillardia pulchella, Solidago sempervirens, Baptisia spp., Indigofera miniata, Eriogonum multiflorum, Conoclinium betonicifolium, and Rudbeckia hirta, are also commonly encountered. Some woody species are found in the system but typically make up very little cover. Cover of woody species is limited but may include Baccharis spp., Opuntia engelmannii var. lindheimeri, Morella cerifera, Quercus fusiformis, Quercus virginiana, and stunted Prosopis glandulosa. Non-native woody species such as Tamarix spp., Schinus terebinthifolius, and Triadica sebifera may be present to dominant. Small areas may have sufficient woody cover to be mapped as a shrubland (Elliott 2011).
Source: NatureServe Explorer
Environment
This system occupies deep eolian sands and Pleistocene barrier island and beach deposits that sit on top of underlying geologic formations, especially the Beaumont Formation. This includes deep sands well inland on the South Texas Sand Sheet, which represents by far the largest continuous patch of this type. It is found on primary and secondary dunes, as well as relatively level areas such as barrier flats, and on the mainland on deep sands of stranded beach ridges. Significant local topography, in the form of swales and pothole wetlands, may be present. Significant surface drainages are generally scarce. Soils are deep or coastal sands (Elliott 2011).
Source: NatureServe Explorer
Dynamics
Substrate, hydrology, drought, coastal processes (including tropical storms) and fire play a role in maintaining this ecological system (Lonard et al. 2004, Morton et al. 2004, Britton et al. 2010). Composition and structure vary depending on these processes.
Source: NatureServe Explorer
Threats
In some areas this system has been virtually eliminated due to conversion to tame pasture, cropland, urban and recreational development, dominance by invasive species, or due to woody plant encroachment because of lack of burning. Threats include habitat conversion, alteration of natural fire regime, sea-level rise, coastal development, habitat degradation from recreational vehicles, and coastal engineering that interferes with sand movement and shoreline migration (Defeo et al. 2009). Increasing sea-level rise associated with global climate change will lead to more loss of coastal grasslands, especially in developed areas where development restricts the potential for inland migration of the grasslands. Invasive plant threats include exotic pasture grasses (such as Bothriochloa ischaemum var. songarica, Dichanthium annulatum, and Urochloa maxima (= Panicum maximum)), Triadica sebifera, and off-site native shrubs such as Baccharis spp. Invasive animals such as imported red fire ants (Solenopsis invicta) and feral hogs (Sus scrofa) prey on the eggs of various animals (Defeo et al. 2009). Feral house cats, dogs, and coyotes are a threat to nesting birds and other small animals which occur in coastal habitats. The recent increase in prevalence of the native grass Heteropogon contortus has raised some concern (Bielfelt 2013).
Source: NatureServe Explorer
Distribution
This system is found in the northern Gulf of Mexico along the Texas coast.
Source: NatureServe Explorer
Ecologically Associated Plant Species
Plant species that characterize this ecosystem type, organized by vegetation stratum. These are species ecologically associated with the ecosystem, not confirmed present in any specific area.
Tree canopy
Schinus terebinthifolius, Triadica sebifera
Herb (field)
Hydrocotyle bonariensis, Oenothera drummondii, Panicum amarum, Paspalum monostachyum, Schizachyrium scoparium ssp. littorale, Sesuvium portulacastrum, Sisyrinchium biforme, Spartina patens, Trichoneura elegans
Source: NatureServe Ecological System assessment
Ecologically Associated Animals (4)
Animal species ecologically associated with this ecosystem type based on NatureServe assessment. These are species whose habitat requirements overlap with this ecosystem, not confirmed present in any specific roadless area.
Source: NatureServe Ecological System assessment
Component Associations (6)
Plant community associations that occur within this ecological system. Associations are the finest level of the U.S. National Vegetation Classification (USNVC) and describe specific, repeating assemblages of plant species. Each association represents a distinct community type that may be found where this ecosystem occurs.
| Name | G-Rank | |
|---|
| Acacia rigidula Shrubland | G4 | NatureServe |
| Panicum amarum - Paspalum monostachyum Grassland | G3 | NatureServe |
| Schizachyrium littorale - Paspalum monostachyum Grassland | G3 | NatureServe |
| Spartina patens - Fimbristylis (caroliniana, castanea) - (Panicum virgatum) Marsh | G2 | NatureServe |
| Spartina patens - Panicum amarum - Hydrocotyle bonariensis Grassland | G2 | NatureServe |
| Uniola paniculata - Panicum amarum - Croton punctatus Grassland | G3 | NatureServe |
State Conservation Ranks (1)
Subnational conservation status ranks (S-ranks) assigned by Natural Heritage Programs in each state where this ecosystem occurs. S1 indicates critically imperiled at the state level, S2 imperiled, S3 vulnerable, S4 apparently secure, and S5 secure. An ecosystem may be globally secure but imperiled in specific states at the edge of its range.
Methodology and Data Sources
Ecosystem classification: Ecosystems are classified using the LANDFIRE 2024 Existing Vegetation Type (EVT) layer, mapped to NatureServe Terrestrial Ecological Systems via a curated crosswalk. Each EVT is linked to the USNVC (U.S. National Vegetation Classification) hierarchy through pixel-level co-occurrence analysis of LANDFIRE EVT and NatureServe IVC Group rasters across all roadless areas.
Vegetation coverage: Coverage percentages and hectares are derived from zonal statistics of the LANDFIRE 2024 EVT raster intersected with roadless area boundaries.
Ecosystem narratives and community species: Sourced from the NatureServe Explorer API, representing professional ecological assessments of vegetation composition, environmental setting, dynamics, threats, and characteristic species assemblages.
IVC hierarchy: The International Vegetation Classification hierarchy is sourced from the USNVC v3.0 Catalog, providing the full classification from Biome through Association levels.
Component associations: Plant community associations listed as components of each NatureServe Ecological System. Association data from the NatureServe Explorer API.
State ranks: Conservation status ranks assigned by NatureServe member programs in each state where the ecosystem occurs.