Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
Figure 1. Mapped extent
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
Major Land Resource Area (MLRA): 080B–Texas North-Central Prairies
MLRA 80B consists of gently rolling, dissected plains with very steep hillsides and
sideslopes and narrow flood plains associated with small streams. Loamy and clayey
soils range from very shallow to deep and developed in sandstones, shales, and
limestones of Pennsylvanian age.
This ecological site is correlated to soil components at the Major Land Resource Area (MLRA) level which is further described in USDA AgHandbook 296.
Ecological site concept
These sites occur on shallow soils with a high amount of surface boulders and stones. The reference vegetation includes a mosaic of mid and tallgrasses and oak trees and other woody shrubs and vines. Without periodic fire or brush management, woody canopy cover will increase and lead to a significant shift in the plant community. Production is often limited by the shallow soil resources and large amount of surface rock.
Sandstone Hill 26-33" PZ
Savannah site with fewer boulders and more herbaceous vegetation.
Sandstone Hill 26-33" PZ
Savannah site with fewer boulders and more herbaceous vegetation.
Table 1. Dominant plant species
(1) Quercus stellata
(1) Schizachyrium scoparium
This site occurs on moderately steep to very steep side slopes of hillslopes and ridges in the Texas North-Central Prairies. This site is characteristically a water shedding site. Slopes range up to 50 percent but are typically 20 to 40 percent.
Table 2. Representative physiographic features
(2) Hills > Ridge
|Runoff class||High to very high|
|Elevation||750 – 2,400 ft|
|Slope||20 – 40%|
Table 3. Representative physiographic features (actual ranges)
|Runoff class||Not specified|
|Slope||8 – 50%|
The climate is subtropical subhumid and is characterized by hot humid summers and relatively mild winters. Tropical maritime air controls the climate during spring, summer and fall. In winter and early spring, frequent surges of polar Canadian air cause sudden drops in temperatures and add considerable variety to the daily weather. The average first frost generally occurs about November 5 and the last freeze of the season usually occurs about March 19. The average frost free period ranges from 215 days in the northern counties, to 240 days in the south.
The average relative humidity in mid-afternoon is about 60 percent in the summer months. Humidity is higher at night, and the average at dawn is about 80 percent. The sun shines 75 percent of the time possible during the summer and 50 percent in winter. The prevailing wind direction is from the southwest and highest windspeeds occur during the spring months.
Approximately 75% of annual rainfall occurs between April 1 and October 31. Rainfall during the months of April through September typically occurs during thunderstorms which tend to be intense and brief, resulting in large amounts of rain in a short time. The wettest months of the year are May, June, September, and October. The driest months during the growing season are July and August. The winter months of November, December, January, and February are the driest months overall.
Average annual precipitation for the entire MLRA is approximately 28 inches. There is a noticeable difference in the average annual precipitation in the northern counties in comparison to the southern and western counties of this Major Land Resource Area. Jack, Clay, Young, and Palo Pinto Counties all have an average annual precipitation of more than 31 inches. Stephens, Eastland, McCulloch, and San Saba Counties all have an average annual precipitation of less than 28 inches.
Winters tend to be mild, with occasional periods of very cold temperatures which can be accompanied by strong northerly winds and freezing precipitation. Snow is infrequent and significant accumulations are rare. These periods of very cold weather are generally short-lived. Summers tend to be hot and dry. Drought conditions are common during most summers. Air temperatures of more than 95oF are common from mid-June through September. In the northern counties nearest to the Red River, temperatures are generally slightly cooler during winter months and slightly warmer during summer months than in the other counties in the North Central Prairie.
Table 4. Representative climatic features
|Frost-free period (characteristic range)||185-202 days|
|Freeze-free period (characteristic range)||212-224 days|
|Precipitation total (characteristic range)||30-33 in|
|Frost-free period (actual range)||183-204 days|
|Freeze-free period (actual range)||210-226 days|
|Precipitation total (actual range)||29-34 in|
|Frost-free period (average)||194 days|
|Freeze-free period (average)||218 days|
|Precipitation total (average)||32 in|
Figure 2. Monthly precipitation range
Figure 3. Monthly minimum temperature range
Figure 4. Monthly maximum temperature range
Figure 5. Monthly average minimum and maximum temperature
Figure 6. Annual precipitation pattern
Figure 7. Annual average temperature pattern
Climate stations used
(1) BOWIE [USC00410984], Bowie, TX
(2) JACKSBORO [USC00414517], Jacksboro, TX
(3) GRAHAM [USC00413668], Graham, TX
(4) BRECKENRIDGE [USC00411042], Breckenridge, TX
(5) MINERAL WELLS AP [USW00093985], Millsap, TX
(6) EASTLAND [USC00412715], Eastland, TX
(7) BROWNWOOD 2ENE [USC00411138], Early, TX
Influencing water features
These sites are in water shedding upland positions with a high amount of surface rock. Therefore, a high amount of runoff can be expected. The presence of adequate ground cover and deep-rooted tallgrass species can help facilitate water infiltration into the soil profile. They are not associated with wetlands.
Representative soil components for this ecological site include: Shatruce
The site is characterized by moderately deep to conglomerate bedrock, rubbly to very rubbly, well drained soils.
Table 5. Representative soil features
(2) Residuum – conglomerate
(3) Colluvium – claystone
(4) Colluvium – conglomerate
(1) Gravelly sandy loam
|Drainage class||Well drained|
|Permeability class||Very slow|
|Soil depth||20 – 40 in|
|Surface fragment cover <=3"||20%|
|Surface fragment cover >3"||20 – 70%|
|Available water capacity
|4 – 6 in|
|Soil reaction (1:1 water)
|4.5 – 7.3|
|Subsurface fragment volume <=3"
|Subsurface fragment volume >3"
Like many sites across the Great Plains, changes in disturbance initiated by permanent settlements has had a profound impact on the ecological dynamics of the ecological sites. Historically, the site was influenced by periodic fires during all seasons of growth. These fires were often the result of dry lightning strikes and/or anthropogenic fires set by Native Americans. The fire frequency during the period prior to settlement is estimated between 2-5 years for the southern Great Plains. These particular sites were rarely subject to the effects of grazing unlike the adjacent sites due to the steep, bouldery terrain.
With the removal of fire and the introduction of conventional livestock fencing, the landscape began to change to more homogenous vegetation patterns and altered plant communities. Gently sloping sites were often broken out for crop production also. This led to a highly fragmented, highly disturbed landscape we see today across much of the southern Great Plains.
While parts of the MLRA are still intact prairie, they often lack the evolutionary fire and grazing interactions that help shape the historic reference plant communities. Without these periodic fires, many sites have transitioned to a woody dominated state.
State and Transitional Pathways:
The following diagram suggests some pathways that vegetation on the ecological site might take in response to various treatments or natural stimuli over time. There may be other states that are not shown on this diagram. This information identifies the changes in plant communities that do occur due to management practices and natural factors. The plant communities described here are commonly observed on this ecological site. The local NRCS field office has information available to assist with planning and development of the plant community for specific purposes.
Changes in plant community makeup may be due to many factors. Change may occur slowly or in some cases, fairly rapidly. As vegetative changes occur, certain thresholds are crossed. A threshold means that once a certain point is reached during the transition of one community to another, a return to the previous state may not be possible without the input of some form of energy. This often means intervention with practices that are not part of natural processes. An example might be the application of herbicide to control some woody species to reduce their population and encourage more grass and forbs growth. Merely adjusting grazing practices would probably not accomplish any significant change in a plant community once certain thresholds are crossed. The amount of energy required to effect change in community would depend on the present vegetative state and the desired change.
State and transition model
More interactive model formats are also available.
View Interactive Models
Oak Savannah - Reference
This is the reference state for the Bouldery Hill ecological site. It represents the historic range of variability in the plant communities with the periodic disturbance of fire. It is a mosaic of herbaceous plants, oak species and woody understory vines and shrubs. The dominant trees are post oak and black jack oak with a mixture of tall and Midgrasses, forbs and shrubs in the understory and canopy interspaces. Dominant herbaceous plants include little bluestem, indiangrass and sideoats grama. Other grasses include dropseeds, sedges, wildryes and scribner’s panicum. Forbs include Sunflowers, tickclover, lespedezas, wildbeans, yellow Neptune, western ragweed and sagewort. Other woody plants include elms, greenbriar, plums, grapes, coralberry, and Carolina snailseed. These woody species will increase in ground cover in the absence of fire. Woody canopy in the reference state is complex with some areas having dense oak canopy mixed with multiple prairie openings. For planning and management purposes, the average woody canopy in reference condition can be described as less than 40%. The Sandy Loam site is estimated to produce between 700 – 2,000 pounds of vegetative production per year in reference condition. Midgrasses greater than Tallgrasses equal Trees greater than Shrubs greater than Forbs
Characteristics and indicators. Plant type / Low/ RV/ High Grass/Grasslike/ 490/ 840/ 1400 Forb/ 35/ 60/ 100 Shrub/Vine/ 70/ 120/ 200 Tree/ 105/ 180/ 300 Total / 700/ 1200/ 2000
Closed Canopy Woodland
This state represents the shift to a woody dominated plant community with woody canopy exceeding 60%. Trees and shrubs dominate the ecological processes on the site and the herbaceous grasses and forbs are limited to shade tolerant species. There is an abundance of leaf litter build up which further limits herbaceous plant germination and production.
State 1 to 2
Without periodic fire or brush management the reference state will transition to the Closed Canopy Woodland state. Woody species will continue to increase and lead to mesophication of the plant community with increased woody canopy and increase in shade tolerant species.
Restoration pathway R2A
State 2 to 1
At this point it will take significant inputs to remove woody species and restore the savannah state. This will require some selective thinning of woody species and the re-introduction of fire to the ecosystem. This process may take 5 years or more depending on woody canopy and past management.
Due to the rough terrain, wildlife species are the dominant grazers and browsers of the site. Various songbirds and small mammals may also find use of these areas. As the site changes towards the woody dominated community, the quality of the habitat may improve for some species and decline for others. Management must be applied to maintain a vegetative state in optimum habitat quality for the desired animal species.
These sites occur on uplands and shed water to adjacent sites lower on the landscape. With a high amount of surface rock, significant runoff may be expected. The presence of deep rooted tallgrasses can help facilitate percolation of water into the soil profile.
Inventory data references
Soil Survey Manuscript Young County, TX
Soil Survey Manuscript Jack County, TX
. 2021 (Date accessed). USDA PLANTS Database. http://plants.usda.gov.
Fuhlendorf, S.D., D.M. Engle, J. Kerby, and R. Hamilton. 2009. Pyric Herbivory: Rewilding Landscapes through the Recoupling of Fire and Grazing. Conservation Biology 23:588–598.
These site descriptions were developed as part a Provisional ESD project using historic soil survey manuscripts, available range site descriptions, and low intensity field traverse sampling.
Updates to legacy drafts by Colin Walden, Soil Survey Region 9
Bryan Christensen, 9/19/2023
Site Development and Testing Plan:
Future work, as described in a Project Plan, to validate the information in this Provisional Ecological Site Description is needed. This will include field activities to collect low-, medium-, and high-intensity sampling, soil correlations, and analysis of that data. Annual field reviews should be done by soil scientists and vegetation specialists. A final field review, peer review, and quality control and quality assurance reviews of the ESD will be needed to produce the final document. Annual reviews of the Project Plan are to be conducted by the Ecological Site Technical Team.
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
|Contact for lead author|
|Approved by||Bryan Christensen|
|Composition (Indicators 10 and 12) based on||Annual Production|
Number and extent of rills:
Presence of water flow patterns:
Number and height of erosional pedestals or terracettes:
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Number of gullies and erosion associated with gullies:
Extent of wind scoured, blowouts and/or depositional areas:
Amount of litter movement (describe size and distance expected to travel):
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
Perennial plant reproductive capability:
The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.