Crosstimbers Oak Forest and Woodland

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Nature Serve ID: CES205.682

Geology

The eastern occurrences of this system are associated with sandy members of the Cretaceous Woodbine Formation, while western occurrences occupy soils derived from the sands of the Cretaceous Trinity Group (such as Paluxy, Antler, and Twin Mountain- Travis Peak Sands). Further west, in the fringe of the Western Crosstimbers, the system occurs on more rugged, rocky and gravelly sites derived from Pennsylvanian formations.

Landform

Gently rolling, moderately dissected uplands, and irregular plains becoming more rugged in the western fringe of the distribution of this system.

Soils

Sands or sandy loams, some with a claypan, are characteristic of this system. Ecological Sites typical of the eastern expressions include Sandy Loam, Tight Sandy Loam, Claypan Prairie, Sandstone Hill, and Sandy. Those more typical of the western expressions include Sandy Loam, Loamy Sand, Tight Sandy Loam, Sandy, and Clay Loam.

Parent Description

This system is generally described as a savanna or woodland dominated by Quercus stellata (post oak) and/or Quercus marilandica (blackjack oak) and occurring in southwest-northeast trending bands separated by the Grand Prairie. Other species in the canopy may include Ulmus crassifolia (cedar elm), Quercus fusiformis (plateau live oak), Celtis laevigata (sugar hackberry), and Juniperus virginiana (eastern redcedar). The understory may have been historically dominated by Schizachyrium scoparium (little bluestem), but current understory composition may be largely determined by land use history and grazing pressure. In the east, where precipitation is greater, tallgrass species such as Andropogon gerardii (big bluestem) and Sorghastrum nutans (Indiangrass) may be important components of the understory, or occupy prairie patches. In the drier west, shortgrass species such as Buchloe dactyloides (buffalograss) become more conspicuous. Other graminoid species that may be present include Schizachyrium scoparium (little bluestem), Paspalum setaceum (fringeleaf paspalum), Sporobolus compositus (tall dropseed), Bouteloua curtipendula (sideoats grama), Bouteloua hirsuta (hairy grama), Bouteloua rigidiseta (Texas grama), Bothriochloa laguroides ssp. torreyana (silver bluestem), Nassella leucotricha (Texas wintergrass), and Aristida spp. (threeawn). Non-native species such as Bromus catharticus (rescuegrass)Cynodon dactylon (Bermuda grass) and Bothriochloa ischaemum var. songarica (King Ranch bluestem) frequently dominate the herbaceous layer. With the disruption of a natural fire cycle, branching of overstory species may be continuous to near ground level, reducing light penetration and leading to reduced herbaceous cover. The shrub layer may contain species such as Smilax bona-nox (greenbrier), Rhus glabra (smooth sumac), Rhus trilobata (skunkbush sumac), Crataegus spp. (hawthorn), and Symphoricarpos orbiculatus (coral-berry). Sites dominated by Prosopis glandulosa (mesquite), sometimes with Ziziphus obtusifolia (lotebush) as a common shrub component, are particularly common to the west. Juniper (including Juniperus virginiana (eastern redcedar), Juniperus ashei (Ashe juniper), and Juniperus pinchotii (redberry juniper), depending on the site) dominated sites are also frequently encountered. Prairie openings and inclusions tend to occur on tighter soils.

The Eastern Crosstimbers occupy a relatively narrow band, approximately 20 miles wide running from McLennan County in the south to the Red River. The Western Crosstimbers is a broader belt, running from about Callahan County in the south, north and east to Montague County. The Western Crosstimbers can further be divided into the Main Belt which has developed on soils derived from the Cretaceous Trinity Group sands, and the more westerly Fringe which has developed on the more rugged and rocky/gravelly sites derived from Pennsylvanian formations.

Ecological Mapping Systems

Crosstimbers: Live Oak Forest and Woodland

Mapping System ID: 502

This vegetation type is a relatively uncommon component of the system, generally occurring in the eastern Crosstimbers on calcareous substrates. Overstory is dominated by Quercus fusiformis (plateau live oak), with Quercus stellata (post oak), Ulmus crassifolia (cedar elm), Prosopis glandulosa (mesquite), and Juniperus ashei (Ashe juniper) also present as minor components of the canopy. In some areas it may be difficult to distinguish occurrences of this vegetation type from occurrences of Edwards Plateau Limestone Savanna and Woodland (CES303.660) representing outliers of that system.

Distribution Map

Crosstimbers: Live Oak Forest and Woodland

Photos

crosstimber_liveoak_forest_site199.jpg

Public Land Occurrence

  • None.

Crosstimbers: Post Oak / Juniper Woodland

Mapping System ID: 503

Sites co-dominated by Juniperus species (Juniperus virginiana (eastern redcedar) to the north and east, and Juniperus pinchotii (redberry juniper) and Juniperus ashei (Ashe juniper) elsewhere are frequently encountered. Such sites, thought to result from disruption in the fire regime, may have Quercus stellata (post oak) and Quercus marilandica (blackjack oak) as co-dominants in the canopy. The dense canopy cover by cedars often results in limited light penetration and the consequent reduction in herbaceous cover. In central and southern portions of the Crosstimbers, areas over limestone substrate that are mapped as this type may be dominated by Quercus buckleyi (Texas oak), Quercus fusiformis (plateau live oak), and Juniperus ashei (Ashe juniper). Ulmus crassifolia (cedar elm) and Celtis laevigata (sugar hackberry) may also be important canopy species.

Distribution Map

Crosstimbers: Post Oak / Juniper Woodland

Photos

crosstimbers_postoak_redcedar_forest_site573.jpg

Crosstimbers: Post Oak Woodland

Mapping System ID: 504

This vegetation type represents the typical occurrence dominated by the usual Quercus stellata (post oak) and Quercus marilandica (blackjack oak), with other canopy species such as Carya texana (black hickory), Ulmus crassifolia (cedar elm), Quercus fusiformis (plateau live oak), Juniperus virginiana (eastern redcedar), and Celtis laevigata (sugar hackberry) present. The overstory may be relatively closed, resulting in reduced herbaceous cover. In some situations, Prosopis glandulosa (mesquite) may be relatively dense. Grass species, particularly Schizachyrium scoparium (little bluestem), are present in the understory, and may form prairie openings in the woodland.

Distribution Map

Crosstimbers: Post Oak Woodland

Photos

crosstimbers_popstoak_woodland_site462.jpg

Crosstimbers: Savanna Grassland

Mapping System ID: 507

This is a primarily herbaceous vegetation type, representing the graminoid dominated component of the savanna as it occurs within this system. Occurrences tend to occur on tighter soils (such as on Clay Loam, Clayey Upland, Claypan Prairie, and Claypan Savanna ecoclasses), but are often dependant on appropriate land management (such as prescribed fire and/or brush control) that ensures reduced woody cover. Woody canopy represents less than 25% cover. Historically, Schizachyrium scoparium (little bluestem) likely dominated these grasslands, but current composition may be largely determined by landuse history and grazing pressure. In the east, where precipitation is greater, tallgrass species such as Andropogon gerardii (big bluestem) and Sorghastrum nutans (Indiangrass) may be important components. In the drier west, shortgrass species such as Buchloe dactyloides (buffalograss) become more conspicuous. Other graminoid species that may be present include Schizachyrium scoparium (little bluestem), Nassella leucotricha (Texas wintergrass), Paspalum setaceum (fringeleaf paspalum), Sporobolus compositus (tall dropseed), Bouteloua curtipendula (sideoats grama)Bouteloua hirsuta (hairy grama)Bouteloua rigidiseta (Texas grama), Bothriochloa laguroides ssp. torreyana (silver bluestem), and Aristida spp. (threeawn). Non-native species such as Cynodon dactylon (bermudagrass), Bromus arvensis (Japanese brome), Bromus tectorum (cheatgrass), and Bothriochloa ischaemum var. songarica (King Ranch bluestem) are often significant components. It may be difficult to distinguish occurrences of this vegetation type from occurrences of Southeastern Great Plains Tallgrass Prairie (CES205.685) to the east and Central Mixedgrass Prairie (CES303.659) to the west. Prosopis glandulosa (mesquite) is a common shrub in this type, and some areas have fairly dense mesquite cover.

 

 

 

 

Distribution Map

Crosstimbers: Savanna Grassland

Photos

crosstimbers_savanna_grassland_site422.jpg

Crosstimbers: Juniper Slope Forest

Mapping System ID: 521

This is a very minor component of the system, occupying slopes greater than twenty percent and dominated by Juniperus ashei (Ashe juniper), Juniperus virginiana (eastern redcedar), or less commonly, Juniperus pinchotii (redberry juniper). This vegetation type is mapped in the southern part of the Western Crosstimbers, where it is frequently associated with slopes on calcareous substrates. These occurrences might be more appropriately considered outliers of Edwards Plateau: Ashe Juniper Slope Forest.

 

 

 

Distribution Map

Crosstimbers: Juniper Slope Forest

Photos

crosstimbers_redcedar_slopeforest_site113.jpg

Crosstimbers: Hardwood / Juniper Slope Forest

Mapping System ID: 523

Forests occupying slopes greater than twenty percent with canopies co-dominated by deciduous hardwood species (such as Quercus stellata (post oak)Quercus buckleyi (Texas oak)Quercus marilandica (blackjack oak)Ulmus crassifolia (cedar elm)) and juniper species (including Juniperus pinchotii (redberry juniper), J. virginiana (eastern redcedar), or J. ashei (Ashe juniper), depending on the site). On some mesic slopes on limestones or chalks of the northern Crosstimbers, and into the Blackland Prairie, Quercus shumardii (Shumard oak) and Quercus muehlenbergii (chinkapin oak) may become the co-dominants in the vegetation type. The overstory canopy tends to be more closed than the upland counterparts, and shrub and herbaceous cover is consequently reduced. Occurrences of this type in the southern part of the Western Crosstimbers frequently occupy slopes on calcareous substrates and may be more appropriately considered as Edwards Plateau Slope forest.

Distribution Map

Crosstimbers: Hardwood / Juniper Slope Forest

Photos

crosstimbers_hardwood_redcedar_slopeforest_site187.jpg

Crosstimbers: Oak / Hardwood Slope Forest

Mapping System ID: 524

These relatively closed canopy forests on slopes (greater than twenty percent) are dominated in the overstory by deciduous species, primarily oaks such as Quercus stellata (post oak)Quercus muehlenbergii (chinkapin oak)Quercus marilandica (blackjack oak)Quercus buckleyi (Texas oak). Ulmus crassifolia (cedar elm)Sideroxylon lanuginosum (gum bumelia), Celtis laevigata (sugar hackberry), and/or Celtis laevigata var. reticulata (netleaf hackberry) may also be common in the canopy. These slopes are frequently associated with the Sandstone Hill, Bouldery Hill, or Rocky Hill ecoclasses, with the substrate often derived from underlying sandstones. Evergreen species such as Quercus fusiformis (plateau live oak) and Juniperus spp. (juniper) may be present, but relatively minor components. On some calcareous slope in the northern part of the Crosstimbers, and into the Blackland Prairie region, Quercus shumardii (Shumard oak) and Quercus muehlenbergii (chinkapin oak) may dominate or co-dominate, with Quercus muehlenbergii (chinkapin oak) tending to dominate drier sites and Quercus shumardii (Shumard oak) dominating more mesic sites. On such mesic sites dominated by Quercus shumardii (Shumard oak), subdominants may include Quercus muehlenbergii (chinkapin oak), Quercus macrocarpa (bur oak), Celtis spp. (hackberry), and Ulmus rubra (slippery elm)

Distribution Map

Crosstimbers: Oak / Hardwood Slope Forest

Photos

Example_Crosstimbers_Oak_Hardwood_Slope_Forest.jpg

Crosstimbers: Sandyland Oak Woodland

Mapping System ID: 534

This vegetation type represents system occurrences that occupy particularly sandy sites (typically Deep Sand, Sand Hill, and perhaps some Sandy ecoclasses), often associated with Paluxy and Antlers Sand or alluvial or eolian deposits. Differentiation of this vegetation type is currently theoretical in anticipation that these sites may be sufficiently distinct to require a separate vegetation type, however field data is largely lacking. These sites are likely dominated by Quercus stellata (post oak) and Quercus marilandica (blackjack oak). Quercus margarettae (sand post oak) may be present in this vegetation type, and sites should be sampled to verify, especially in Eastland and Comanche counties on Antlers Sand or sandstone members of the Twin Mountains Formation. Carya texana (black hickory), Ulmus crassifolia (cedar elm), and Celtis laevigata (sugar hackberry) may be well-represented in the overstory.

Distribution Map

Crosstimbers: Sandyland Oak Woodland

Photos

crosstimbers_sandyland_woodland_site5.jpg