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.
Major Land Resource Area (MLRA): 070A–High Plateaus of the Southwestern Great Plains
This site is only applicable to the Canadian Plateaus LRU of MLRA 70A (LRU 70A.1).
This site is only applicable to the Canadian Plateaus LRU of MLRA 70A (LRU 70A.1). Please refer to the following key:
Land Resource Unit (LRU) Key for MLRA 70A
– High Plateaus of the Southwestern Great Plains
1a. The site exists on a landform of volcanic origin, such as a basalt plateau, or is part of an escarpment system that rises directly to a volcanic structure. These escarpments are included if they have volcanic alluvium or colluvium (i.e. basalt, rhyolite, tuff, cinders) overlying non-volcanic residuum or bedrock (i.e. sandstone, shale). → VOLCANIC PLATEAUS LRU (VP)
User tip: Other alluvial or colluvial landform features extending below the escarpments are not included unless they have a predominance of volcanic fragments at the surface. Also, note that playas atop volcanic plateaus are included within the VP-LRU.
1b. All other sites. → 2
2a. The site exists in the annulus or floor of a playa. → CANADIAN PLATEAUS LRU (CP)
User tip: Small islands of playas occur within large areas of HP-LRU. These sites may be far from the nearest CP landform but will still key-out to the CP-LRU. The playa rim components, however, may key out to either LRU, so it is important to properly identify their soil properties.
2b All other sites. → 3
3a. The site is part of an escarpment landscape complex (defined below) or is within a canyon, valley, or small basin confined by such escarpments. At the upper boundary of the LRU, the soil surface meets at least 4 of the following 5 criteria:
I. Shallow or very shallow soils are present in at least 50% of the landform area;
II. Soils are underlain by sandstone bedrock of the Cretaceous Dakota Formation or older;
III. Presence or historical evidence of a conifer stand (≥ 2% canopy cover);
IV. The ground surface has a slope of at least 10%;
V. The landforms drain towards steep-walled escarpments or canyons below the Dakota sandstone (older Jurassic and Triassic Formations underlie this sandstone mesa cap).
→ MESOZOIC CANYONS AND BREAKS LRU (MCB)
User tip: The MCB sites also occur on any colluvial or alluvial bottomlands confined within escarpments or canyons. Some valleys transition from CP to MCB, or back to CP, and the turning point can be difficult to determine. Generally, the landforms are part of the MCB when confined between Dakota sandstone breaks or escarpments on both sides. Much of the acreage in the MCB is aproned by colluvial debris fans—composed of sandy materials with large sandstone fragments visible on the soil surface, including large stones or boulders. The soils in the bottoms of these confined valleys will also be in the MCB. When the valley opens, or there is only a single escarpment opening to the plains, the landforms below the steeper, rockier escarpments will be members of the CP-LRU.
3b. Fewer than 4 of the above criteria are met. → 4
4a. The soil is on a plateau summit position (tread) and is within 50 cm to contact with either plateau bedrock (non-soil bedrock of cemented sandstone, limestone, or shale) or strath terrace cobbles, but not a petrocalcic contact (caprock or caliche of cemented calcium carbonate). → CANADIAN PLATEAUS LRU (CP)
4b. No plateau bedrock or strath terrace cobbles within 50 cm. → 5
5a. Fragments (>2 mm) are visible within the soil profile and/or on the surface. If fragments cannot be found in the profile, it is acceptable to look nearby on ant mounds or around burrows. If site is in a drainageway, one can look for fragments on landforms immediately upslope.→ 6
5b. Fragments are entirely absent. → 7
6a. Fragments are mostly petronodes or High Plains gravels. → HIGH PLAINS LRU (HP)
6b. Fragments are mostly plateau bedrock fragments. → CANADIAN PLATEAUS LRU
7a. All horizons in the upper 100 cm of soil have textures of sandy clay loam or sandier.
→ CANADIAN PLATEAUS LRU (CP)
7b. At least one horizon in the upper 100 cm of soil has a texture that is less sandy than sandy clay loam. → HIGH PLAINS LRU (HP)
NRCS and BLM: Sandy Canadian Plateaus LRU Major Land Resource Area 70A, High Plateaus of the Southwestern Great Plains Land Resource Region G, Western Great Plains Range and Irrigated Region (United States Department of Agriculture, Natural Resources Conservation Service, 2006).
USFS: Sandy Smooth High Plains Subsection Southern High Plains Section Great Plains-Palouse Dry Steppe Province (Cleland, et al., 2007).
EPA: Sandy <26l Upper Canadian Plateau<26 Southwestern Tablelands (Griffith, et al. 2006).
Ecological site concept
The Sandy ecological site occurs on plateau summits in the Canadian Plateaus LRU (CP). This LRU occupies the western portion of MLRA 70A and extends from Las Vegas, NM at the southern end to beyond Raton, NM at its northern end. Elevation for the LRU ranges from 5,000 to 7,500 feet.
The ecological site concept for the Sandy site is a soil with a depth no shallower than 30 inches (75 centimeters), and typically over 80 inches (200 centimeters) to lithic contact with Dakota sandstone or paralithic contact with weathered Cretaceous shale. Surface textures range from sand to sandy loam, subsurface textures are sandy clay loams or coarser. These surface textures select for distinct plant communities, and differentiate the Sandy site from all other sites on the plateau summits of the Canadian Plateaus that occur on soils greater than 30 inches (75 centimeters) deep.
This site occurs where soils surfaces have strong or violent effervescence and ≥ 5% calcareous rock fragments.
This site occurs in soils that have < 50% sand in subsurface horizons.
This site occurs in soils that have high clay and < 50% sand in textures of subsurface horizons. Typically, these soils are on more stable landforms that have resisted erosion, or else they have subsurface horizons derived from shale residuum.
This site occurs where soils have paralithic contact within 50 cm, and their surfaces lack one or both of the following: strong or violent effervescence and = 5% calcareous rock fragments.
This site occurs on terraces above perennial streams where the flooding frequency interval is ≥ 10 years. This site is often used for hay and small grain production. Adjacent Sandy sites may contribute water to this site via run-on and through-flow.
This site occurs where soils are ≤ 50 cm to lithic contact with sandstone bedrock, and often supports oneseed juniper savannahs.
This site occurs where soils are ≤ 50 cm to lithic contact with limestone bedrock, and often supports oneseed juniper savannahs.
This site occurs in playas. Adjacent Sandy sites contribute water to this site via through-flow.
The Sandy Plains ecological site are correlated to some soil components from the Sandy Plains site.
Deep Loamy Plains
The Sandy site is correlated to a soil component that is currently correlated to the Deep Loamy Plains (R077BY034NM) site. Being MLRA 77B sites, these sites are lower in elevation, therefore warmer; and further east, therefore moister than MLRA 70A, but should exhibit some similarities to these plant communities, and will serve as useful references.
High Sandy Loam
The Sandy site is correlated to soil components that are currently correlated to the High Sandy Loam (R077BY035NM)site. These sites are lower in elevation, therefore warmer; and further east, therefore moister than MLRA 70A, but should exhibit some similarities to these plant communities, and will serve as useful references.
Table 1. Dominant plant species
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