Tamaulipan Floodplain

Geology

Quaternary alluvium.

Landform

Floodplains of rivers and large creeks where sediment is deposited. Topography is relatively level with some relief associated with levees and depressions developed from meanders of the waterway, or historical meanders of the Rio Grande (Resaca).

Soils

Alluvial soils of the Bottomland Ecological Sites, including loamy, clayey, and sandy. The Lowland Ecological Site type also supports this system.

Parent Description

This ecological system occurs along rivers and major drainages in south Texas from the central portion of the Nueces River south to northeastern Mexico and west to the vicinity of Del Rio, Texas. Generally, the system is expressed as a deciduous woodland or forest with tree height reaching to 15 meters, and canopy cover variable but sometimes reaching near 100 percent. The canopy may have a conspicuous (sometimes dominant to co-dominant) evergreen component of species such as Ebenopsis ebano (Texas ebony) and Ehretia anacua (anacua). Dominant species of the overstory canopy often includes one or more of the following species: Celtis laevigata (sugar hackberry), Ulmus crassifolia (cedar elm), Fraxinus berlandieriana (Mexican ash), Prosopis glandulosa (honey mesquite), Acacia farnesiana (huisache), Diospyros texana (Texas persimmon), Leucaena pulverulenta (tepeguaje), Celtis ehrenbergiana (granjeno), Sapindus saponaria var. drummondii (western soapberry), Ebenopsis ebano (Texas ebony), Ehretia anacua (anacua), and Parkinsonia aculeata (retama). In northern portions of the range of this system, particularly within the Nueces River drainage, Carya illinoinensis (pecan) and Quercus fusiformis (plateau live oak) may be conspicuous components of the overstory. Forests and woodlands may have significant shrub cover including saplings of the overstory species in addition to species such as Zanthoxylum fagara (colima), Condalia hookeri (brasil), Forestiera angustifolia (desert olive), Sideroxylon spp. (bumelias), Aloysia gratissima (whitebrush), Acacia greggii var. wrightii (Wright's acacia), Malpighia glabra (Barbados cherry), Guaiacum angustifolium (guayacan), Ziziphus obtusifolia (lotebush) and Amyris texana (Texas torchwood). Other shrub species, such as Buddleja sessiliflora (Rio Grande butterflybush), Phaulothamnus spinescens (snake-eyes), Lippia alba (white lipia), and Amyris madrensis (Sierra Madre torchwood) may be encountered in southern expressions of the system. Salix nigra (black willow) may dominate sites, especially at river's edge and wet sites. Riverbanks and other sites with a reduced overstory canopy (either from disturbance or prolonged inundation) may also be shrub dominated, often with one or few species such as Baccharis neglecta (Rooseveltweed), Baccharis salicifolia (seepwillow), Arundo donax (giant reed), Sesbania drummondii (rattlebox sesbania), or Cephalanthus occidentalis (common buttonbush), and Salix exigua (Texas sandbar willow), Mimosa asperata (black mimosa), or Cephalanthus salicifolius (willowleaf buttonbush) in the lower Rio Grande Valley. The herbaceous layer is typically not well developed, but may include species such as Trichloris pluriflora (multiflower false Rhodes grass), Setaria scheelei (southwestern bristlegrass), Panicum virgatum (switchgrass), Paspalum langei (rustyseed paspalum), Paspalum denticulatum (longtom), Carex crus-corvi (crowfoot sedge), Cyperus articulatus (jointed umbrellasedge), Rivina humilis (pigeonberry), Calyptocarpus vialis (straggler daisy), Chromolaena odorata (cruciata), Teucrium cubense (Cuban germander), Urtica chamaedryoides (slim stinging nettle), Parietaria pensylvanica (cucumberweed), Verbesina microptera (southern frostweed), Chloracantha spinosa (spiny aster), Parthenium confertum (false ragweed), and Malvaviscus arboreus var. drummondii (Drummond Turk's cap). Vines such as Serjania brachycarpa (littlefruit sipple-jack), Cocculus diversifolius (orientvine), Clematis drummondii (old man's beard), and Cissus trifoliata (ivy treebine) are frequently encountered, and Tillandsia usneoides (Spanish moss) often drapes the branches of overstory species. Non-native grasses such as Cynodon dactylon (bermudagrass), Urochloa maxima (guineagrass), Pennisetum ciliare (buffelgrass), Bothriochloa ischaemum var. songarica (King Ranch bluestem), and Bromus catharticus (rescuegrass) are often present to dominant, and sometimes to the exclusion of most other herbaceous species.