Join us from 6:30-8:00pm, Georgetown Public Library, Classroom • NPAT Executive Director, Pat Merkord, will preside over the NPAT…Read more of this >>
2nd Annual Savage Cabbage BashSaturday from 9:00 a.m. to NoonCome out to support our wildflowers!Join students in this “invasive species public awareness event”. Location: Trinity…Read more of this >>
Saturday and Sunday—NPAT’s “Open Preserve” Location: Rolling Plains on NPAT’s Maddin…Read more of this >>
The Edwards Plateau region comprises an area of West Central Texas commonly known as the “hill country.” It is bounded on the east and south by the Balcones Fault. To the north it extends to the Western Cross Timbers of the Oak Woods and Prairies region and grades into the Plains regions. The Pecos River and eastern edge of the Stockton Plateau define the western extent of the Edwards Plateau region.
Elevations range from slightly less than 100 feet to over 3 ,000 feet. Several river systems dissect the surface, creating a rough and well-drained landscape. Average annual rainfall increases from west to east, ranging from 15 to 33 inches. Seasonal rainfall patterns peak in May/June and in September. Soils of the Edwards Plateau are usually shallow with a variety of surface textures. They are underlain by limestone.
Man-made lakes, ranches, and farms are scattered throughout the region.
Scrub forest is the most characteristic plant association of the area. Ash, juniper, Texas oak, and stunted live oak are dominant in the more dissected southern and eastern canyonlands of the region. Mesquite occurs throughout the Edwards Plateau; together with live oak, it dominates the wood vegetation in the west. Some savanna type vegetation also occurs and was formerly more widespread.
According to Correll and Johnon, the most important climax grasses of the Plateau include switchgrass, several species of bluestems and gramas, Indian grass, Canada wild-rye, curly mesquite and buffalo grass, with the rough, rocky areas typically supporting a tall or mid-grass understory and a brush overstory complex made up primarily of live oak, Texas oak, shinnery oak, junipers and mesquite.
The northwestern portion of the Edwards Plateau transitions into “mesquite-tobosa country” similar to that of the Rolling Plains, whereas the Stockton Plateau portion supports the shorter vegetation of semi-desert grassland (Correll and Johnson). Throughout the region, the brush species are generally considered as “invaders” with the climax largely grassland or open savannah, except on the steeper, rockier canyon slopes which have continually supported a dense cedar-oak- thicket.
The Plateau is a region of high endemism, such as netleaf forestiera (Forestiera reticulata), plateau milkvine (Matelea edwardsensis), basin bellflower (Campanula Reverchonii), Lindheimer crownbeard (Verbesina Lindheineri), Lythrum ovalifolium, Tridens Buckleyanus, twisted-leaf yucca (Yucca rupicola), sotol (Dasylirion heteracanthium ), bracted twist-flower (Streptanthus bracteatus ) and cliff bedstraw (Galium Correllii) (Correll and Johnson). In addition to endemism, the Plateau flora reveals a close relationship to that of Mexico (Correll and Johnson).
Included in the Edwards Plateau is the Llano Uplift area. Geologically the region is a large dome with rolling to hilly topography. Granite exfoliation domes, the largest of which is known as Enchanted Rock, are common. In contrast to the clays and clay loams of the Edwards Plateau, sandy soils predominate on the Llano Uplift. Rainfall averages about 30 inches, peaking in May or June and September. Oak and oak-hickory woodlands are common vegetational types, along with mesquite savanna and some grassland types that were once more widely distributed. The Savanna occurs on loamier soils underlain by caliche.