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Edwards Plateau

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Name	†	Color on Map	EPA Code‡
Edwards Plateau Woodland	○		30a
Llano Uplift	○		30b
Balcones Canyonlands	○		30c
Semiarid Edwards Plateau	○		30d

† Status: ✓ = Complete ○ = Needs Image … = Incomplete ∅ = Stub Only

‡ This code refers to the US EPA's Level 4 ecoregion codes for the continental U.S., see here.

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↑About the Edwards Plateau

The Edwards Plateau is a region in central Texas. It stretches a bit farther in the east-west direction than north-south, and is relatively oval-shaped although there is a small discontiguous piece in the northwest.

The climate changes considerably over this region. The east of the region is towards the warm, dry end of a humid subtropical climate; the south has a hot semiarid (subtropical steppe) climate and the north a cold semiarid (mid-latitude steppe) climate. Precipitation is seasonal, following a bimodal pattern with wetter spring and fall, and drier summer and winter. Winters have slightly lower rainfall than summer, but this difference is offset by hotter summer temperatures.

This region is a large dissected limestone plateau; the terrain is much hillier in the south and east. Most of the region is relatively flatter, with rolling hills and broad valleys, although there are some areas of steeper ridges and canyons throughout. Soils are mostly mollisols, deep, fertile soils that formed under grasslands; the soils tend to be somewhat thinner on ridges and hilltops, and deeper on plains and valley floors. The drainage network here is sparse, but streams tend to be perennial, clear, and cool in temperature, often spring-fed. Streams mostly flow over a mix of bedrock, cobble, gravel, and sand. There is significant Karst topography throughout, with sinkholes, underground fissures, and caves, often filling with water and forming extensive aquifers that stabilize the water supply in streams even as rainfall varies seasonally.

Historically, this region was mostly covered in either juniper-oak savanna or mesquite-oak savanna in the drier portions. Dominant trees included Texas live oak (Quercus fusiformis), Texas red oak (Quercus buckleyi), and ashe juniper (Juniperus ashei). Dominant grasses include little bluestem (Schizachyrium scoparium), yellow indiangrass (Sorghastrum nutans), and side-oats grama (Bouteloua curtipendula). Plant diversity is highest in the Balcones Canyonlands in the southeast of the region, where there is more moisture availability; that region has a large portion of endemic species, as well as many more moisture-loving eastern species at or near their westernmost range limits. A combination of fire suppression and grazing has led to a massive increase in the portion of Ashe Juniper, which is rather fire-intolerant but heavily resistant to grazing. Although it is native, ranchers here tend to view it as an invasive species.

Land use here is not particularly intensive, with most of the land used for livestock grazing, including beef cattle, sheep, and goats. There are also extensive private lands managed for wildlife, where people earn their income from hunting leases. There is also significant tourism and recreation. Although most of the region is sparsely populated and rural, the westernmost portion of the Austin metro area is within this region, and a smaller portion of the northwesternmost portions of the San Antonio and San Marcos metro areas are also here. Outside of the outskirts of these larger metro areas, the largest cities located within this region are Kerrville, followed by Boerne, and Fredericksburg. Other towns under 10,000 people include, in descending order of population, Brady, Dripping Springs, Llano, Ozona, Sonora, Big Lake, Eden, Junction, Mason, Eldorado, Menard, and Rocksprings. The western portions of this region are more sparsely populated, reflecting the lack of water.

In the east of this region, it is bordered to the southeast by the flatter Texas Blackland Prairies, a region that historically had open tallgrass prairie but is now heavily populated and also heavily utilized for cropland. That border marks a well-defined geographic transition. Southwest of the end of that region, there is a border to the south with the warmer, drier Southern Texas Plains, and west of that there is a large border to the south and southwest with the Chihuahuan Deserts. This border is less well-defined and is based on a drier climate, but the exact border is subjective. There is a small border to the northwest with the High Plains, and east of that, a brief border to the north with the irregularly-shaped Southwestern Tablelands. East of that there is a border to the north with the Central Great Plains. The eastern portion of this region has a long border to the northeast with Cross Timbers.

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