Blackgap soil and landscape
Soil Profile: Blackgap very gravelly loam in an area of Blackgap-Rock outcrop complex, 10 to 30 percent slopes. Hard limestone bedrock ranges in depth from 7 to 20 inches (18 cm to 51 cm). (Soil Survey of Big Bend National Park, Texas by James Gordon, Soil Scientist, James A. Douglass, Soil Scientist, and Dr. Lynn E. Loomis, Soil Scientist, Natural Resources Conservation Service)
Landscape: An area of Blackgap-Rock outcrop complex, 1 to 16 percent slopes. This area shows vegetation such as Texas false agave, creosotebush, and Chino grama growing on a backslope. This map unit is in the Limestone Hill and Mountain 8-14" PZ ecological site of
MLRA 81D—Southern Edwards Plateau.
Map Unit Setting
Major land resource area (MLRA): MLRA 81D—Southern Edwards Plateau
Elevation: 1,925 to 3,910 feet
Mean annual precipitation: 10 to 13 inches
Mean annual air temperature: 68 to 72 degrees F
Frost-free period: 240 to 280 days
Map Unit Composition
Blackgap and similar soils: 85 percent
Rock outcrop: 10 percent
Dissimilar minor components: 5 percent
Minor components:
Unnamed, minor components soils—5 percent; not hydric
Blackgap soils--
Soil taxonomic classification: Loamy-skeletal, carbonatic, hyperthermic Lithic Ustic Haplocalcids
Typical Profile
Ak—0 to 5 inches; very gravelly loam
Bk—5 to 11 inches; extremely cobbly silt loam
R—11 to 21 inches; limestone bedrock
Setting
Landscape: Dissected plateaus
Landform: Hills, ridges
Landform position (two-dimensional): Summit, shoulder, backslope
Slope: 1 to 16 percent
Down-slope shape: Linear
Across-slope shape: Convex
Representative aspect: Southeast
Aspect range: All aspects
Soil temperature class: Hyperthermic
Soil temperature regime: Hyperthermic
Soil moisture class: Aridic (torric)
Properties and Qualities
Runoff class: Very high
Parent material: Residuum and colluvium derived from thick-bedded limestone bedrock
Depth to restrictive feature: 7 to 20 inches to lithic bedrock
Frequency of flooding: None
Frequency of ponding: None
Depth to water table: More than 72 inches
Drainage class: Well drained
Shrink-swell potential: Low (about 1.5 LEP)
Salinity maximum: Not saline (about 1.0 dS/m)
Sodicity maximum: Not sodic
Calcium carbonate maximum: 47
Available water capacity: Very low (about 1.1 inches)
Gypsum maximum: None
Interpretive Groups
Land capability subclass (nonirrigated): 7s
Hydric soil rating: No
Hydrologic soil group: D
Vegetation
Existing plants: Chino grama, lechuguilla, creosotebush, guayacan, Big Bend silverleaf, sideoats grama, black grama, candelilla, slim tridens, Texas false agave, perennial forbs, other perennial grasses, other shrubs.
Ecological site name and identification: Limestone Hill and Mountain 8-14" PZ (R081DY592TX)
For additional information about the survey area, visit:
www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/texas/bigbendT...
For a detailed soil description, visit:
soilseries.sc.egov.usda.gov/OSD_Docs/B/BLACKGAP.html
For acreage and geographic distribution, visit:
Blackgap soil and landscape
Soil Profile: Blackgap very gravelly loam in an area of Blackgap-Rock outcrop complex, 10 to 30 percent slopes. Hard limestone bedrock ranges in depth from 7 to 20 inches (18 cm to 51 cm). (Soil Survey of Big Bend National Park, Texas by James Gordon, Soil Scientist, James A. Douglass, Soil Scientist, and Dr. Lynn E. Loomis, Soil Scientist, Natural Resources Conservation Service)
Landscape: An area of Blackgap-Rock outcrop complex, 1 to 16 percent slopes. This area shows vegetation such as Texas false agave, creosotebush, and Chino grama growing on a backslope. This map unit is in the Limestone Hill and Mountain 8-14" PZ ecological site of
MLRA 81D—Southern Edwards Plateau.
Map Unit Setting
Major land resource area (MLRA): MLRA 81D—Southern Edwards Plateau
Elevation: 1,925 to 3,910 feet
Mean annual precipitation: 10 to 13 inches
Mean annual air temperature: 68 to 72 degrees F
Frost-free period: 240 to 280 days
Map Unit Composition
Blackgap and similar soils: 85 percent
Rock outcrop: 10 percent
Dissimilar minor components: 5 percent
Minor components:
Unnamed, minor components soils—5 percent; not hydric
Blackgap soils--
Soil taxonomic classification: Loamy-skeletal, carbonatic, hyperthermic Lithic Ustic Haplocalcids
Typical Profile
Ak—0 to 5 inches; very gravelly loam
Bk—5 to 11 inches; extremely cobbly silt loam
R—11 to 21 inches; limestone bedrock
Setting
Landscape: Dissected plateaus
Landform: Hills, ridges
Landform position (two-dimensional): Summit, shoulder, backslope
Slope: 1 to 16 percent
Down-slope shape: Linear
Across-slope shape: Convex
Representative aspect: Southeast
Aspect range: All aspects
Soil temperature class: Hyperthermic
Soil temperature regime: Hyperthermic
Soil moisture class: Aridic (torric)
Properties and Qualities
Runoff class: Very high
Parent material: Residuum and colluvium derived from thick-bedded limestone bedrock
Depth to restrictive feature: 7 to 20 inches to lithic bedrock
Frequency of flooding: None
Frequency of ponding: None
Depth to water table: More than 72 inches
Drainage class: Well drained
Shrink-swell potential: Low (about 1.5 LEP)
Salinity maximum: Not saline (about 1.0 dS/m)
Sodicity maximum: Not sodic
Calcium carbonate maximum: 47
Available water capacity: Very low (about 1.1 inches)
Gypsum maximum: None
Interpretive Groups
Land capability subclass (nonirrigated): 7s
Hydric soil rating: No
Hydrologic soil group: D
Vegetation
Existing plants: Chino grama, lechuguilla, creosotebush, guayacan, Big Bend silverleaf, sideoats grama, black grama, candelilla, slim tridens, Texas false agave, perennial forbs, other perennial grasses, other shrubs.
Ecological site name and identification: Limestone Hill and Mountain 8-14" PZ (R081DY592TX)
For additional information about the survey area, visit:
www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/texas/bigbendT...
For a detailed soil description, visit:
soilseries.sc.egov.usda.gov/OSD_Docs/B/BLACKGAP.html
For acreage and geographic distribution, visit: