Texas Hill Country Limestone Shrubland

This ecological system occurs as a matrix on relatively thin-soiled surfaces of plateaus of the massive limestones such as the Edwards limestone. These short to tall shrublands are variable in density depending on the relative amount of, and depth to, bedrock. Quercus sinuata var. breviloba is an important component of the system, with some areas dominated by Quercus fusiformis. Juniperus ashei is often an important component of this system. Important components in western examples may include Pinus remota, Quercus mohriana, Quercus vaseyana, and Juniperus pinchotii. Herbaceous cover may be patchy and is generally graminoid with species including Schizachyrium scoparium, Bouteloua curtipendula, Bouteloua rigidiseta, Bouteloua trifida, Hilaria belangeri, Bothriochloa laguroides ssp. torreyana, Nassella leucotricha, Erioneuron pilosum, Aristida spp., and others. Disturbances such as fire may be important processes maintaining this system. However, it appears to persist on thin-soiled sites. In the western portions of the Edwards Plateau, more xeric conditions lead to the slow succession of sites to woodlands, resulting in long-persisting shrublands.

This system may be represented by extensive continuous shrub cover, or occur as a discontinuous shrubland, often with scattered emergent overstory trees. Quercus sinuata var. breviloba, Quercus fusiformis, and/or Juniperus ashei may be important components of the system. In the interior of the Edwards Plateau ecoregion, Quercus sinuata var. breviloba is an important component, with some areas dominated by a shinnery of Quercus fusiformis, although monotypic stands of Quercus fusiformis occupying the shrub layer are uncommon. In the west, Pinus remota may also contribute to a scattered emergent overstory. Shrub cover may be dominated by these species, or may be represented as an assemblage of a rather diverse array of species including Rhus virens, Rhus lanceolata, Cercis canadensis var. texensis, Forestiera pubescens, Forestiera reticulata, Ungnadia speciosa, Sophora secundiflora, Diospyros texana, Salvia ballotiflora, Mimosa borealis, Condalia hookeri, Rhus trilobata, Opuntia engelmannii var. lindheimeri, and Mahonia trifoliolata. In the northwest corner of the ecoregion, this system may occur as a Quercus mohriana-dominated shrubland (a type more common in the Southern Shortgrass Prairie ecoregion), often sharing dominance with Juniperus pinchotii. Towards the southwest, Quercus vaseyana (= Quercus pungens var. vaseyana) becomes an important component of the system, and areas dominated by Sophora secundiflora, Diospyros texana, and other shrub species become more common. In the southwest corner of the ecoregion, on the Stockton Plateau, this system may be represented by Acacia berlandieri shrublands. Where shrub cover is distributed in a patchy mosaic, such sites may be used by black-capped vireos (Vireo atricapilla). Herbaceous cover may be patchy and is generally graminoid-dominated with species including Schizachyrium scoparium, Bouteloua curtipendula, Bouteloua rigidiseta, Bouteloua trifida, Hilaria belangeri, Bothriochloa laguroides ssp. torreyana, Nassella leucotricha, Erioneuron pilosum, Aristida spp., and others (Elliott 2011).

This system occurs on thin soils over massive limestone such as Edwards or related formations in the Edwards Plateau of Texas. It may occur on plateaus or slopes and may often form a discontinuous band around a plateau edge as it breaks into the adjacent slope. Soils are characterized by Shallow or Very Shallow Ecological Sites, but may also be found on Low Stony Hill Ecological Sites (Elliott 2011).

This system occurs in a steady state on thin-soiled xeric sites. Shrub cover can be 100% in patches, but overall cover may be 40-50%. Patches of dense shrubs may be interspersed with bare rock and grasslands over shallow soil. Farther west this system grades into other shallow-soiled shrubland systems. Disturbances such as fire may be important processes maintaining this system. However, it appears to persist on thin-soiled sites. In the western portions of the Edwards Plateau, more xeric conditions lead to the slow succession of sites to woodlands resulting in long-persisting shrublands.

This system is limited in occurrence to the Edwards Plateau of Texas.