Natural Resources
Conservation Service
Major Land Resource Area 040X
Major Land Resource Area
Accessed: 04/23/2026
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Description
Major Land Resource Area (MLRA) 40 is the portion of Sonoran Desert that extends from northwest Mexico into southwestern Arizona and southeastern California. This MLRA is hot desert characterized by bimodal precipitation coupled with hot summers and mild winters. These conditions give rise to a rich biological diversity visually dominated by columnar cactus (saguaro) and leguminous trees (palo verde). This unit occurs within the Basin and Range Physiographic Province and is characterized by numerous mountain ranges that rise abruptly from broad, plain-like valleys and basins. Igneous and metamorphic rock classes dominate the mountain ranges, and basin sediments are combinations of fluvial, lacustrine, colluvial and alluvial deposits.
Key publications
Geographic subunits
Land Resource Unit 1 Land Resource Unit (LRU) 40-1, Upper Sonoran Desert, is characterized by desert scrub vegetation with no desert pavement present. Trees grow on uplands as well as in washes and on hillslopes. Elevations range from 2000 to 3800 feet, and precipitation averages 10 to 13 inches per year. Vegetation includes saguaro, palo verde, mesquite, creosotebush, triangle bursage, prickly pear, cholla, limberbush, wolfberry, bush muhly, threeawns, ocotillo, and globe mallow. The soil temperature regime is thermic and the soil moisture regime is typic aridic.
Land Resource Unit 2 Land Resource Unit (LRU) 40-2, Middle Sonoran Desert, is characterized by desert scrub vegetation with a moderate percentage of desert pavement on relic fan remnants; trees are common in all washes, bottoms and hillslopes but largely absent from uplands. Elevation ranges from 1200 to 2000 feet and precipitation averages 7 to 10 inches per year. Upland vegetation includes saguaro, palo verde, creosotebush, white bursage, brittlebush, prickly pear, cholla, desert saltbush, wolfberry, and big galleta. The soil temperature regime is hyperthermic and soil moisture regime is typic aridic.
Land Resource Unit 3 Land Resource Unit (LRU) 40-3, Colorado Sonoran Desert, is characterized by desert scrub vegetation and a high percentage of desert pavement on relic fan remnants. Trees are limited to large washes and hillslopes. Elevations range from 300 to 1200 feet and precipitation averages 3 to 7 inches per year. Vegetation includes creosotebush, white bursage, brittlebush, Mormon tea, teddybear cholla, elephant tree, smoke tree, ocotillo, and big galleta. Soil temperature regime is hyperthermic and soil moisture regime is typic aridic.
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Ecological sites
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Soil texture
Broad visual assessment of uplands with slopes <15%. Desert pavement present, elevations <2,000' above sea level
Broad visual assessment of uplands with slopes <15%. Desert pavement absent; elevations generally >2,000' above sea level
Leguminous trees present in all washes and drainages; generally absent from uplands between them
Leguminous trees ONLY present in largest washes
Bottom position (plant community reliant upon run-on from valley-side or over-bank)
Upland position (plant community reliant upon on-site precipitation, run-on ≤ run-off)
Bottom position (plant community reliant upon run-on from valley-side or over-bank)
Upland position (plant community reliant upon on-site precipitation, run-on ≤ run-off)
Bottom position (plant community reliant upon run-on from valley-side or over-bank)
Upland position (plant community reliant upon on-site precipitation, run-on ≤ run-off)
Slightly to strongly saline soils (ECe ≥ 4 dS/m)
R040XB227AZ – Saline Bottom 7"-10" p.z.
R040XB227AZ – Saline Bottom 7"-10" p.z.
Non-saline to very slightly saline soils (ECe < 4 dS/m)
Soils with water table available to plant community
Soils without a water table available to the plant community
Soils with visible reduction-oxidation features
F040XB215AZ – Sandy Bottom, Woodland 7" - 10" p.z.
F040XB215AZ – Sandy Bottom, Woodland 7" - 10" p.z.
Soils without reduction-oxidation features
F040XB214AZ – Loamy Bottom, Woodland 7"-10" p.z.
F040XB214AZ – Loamy Bottom, Woodland 7"-10" p.z.
Narrow drainage, active channel ≤4' width
R040XB229AZ – Sandy Loam Drainage 7"-10" p.z.
R040XB229AZ – Sandy Loam Drainage 7"-10" p.z.
Wide drainage, active flow path >4' width
Soils sandy
R040XB216AZ – Sandy Wash 7"-10" p.z.
R040XB216AZ – Sandy Wash 7"-10" p.z.
Soils fine sandy loam to clay loam
R040XB211AZ – Loamy Swale 7"-10" p.z.
R040XB211AZ – Loamy Swale 7"-10" p.z.
Soils clayey
R040XB203AZ – Clayey Swale 7"-10" p.z.
R040XB203AZ – Clayey Swale 7"-10" p.z.
Slightly to strongly saline soils (ECe ≥ 4 dS/m)
Non-saline to very slightly saline soils (ECe < 4 dS/m)
Soils sandy, eolian
R040XB224AZ – Sandy Upland, Saline 7"-10" p.z.
R040XB224AZ – Sandy Upland, Saline 7"-10" p.z.
Soils sandy loam
R040XB226AZ – Sandy Loam Upland, Saline 7"-10" p.z.
R040XB226AZ – Sandy Loam Upland, Saline 7"-10" p.z.
Soils loam to clay loam
R040XB225AZ – Loamy Upland, Saline 7"-10" p.z.
R040XB225AZ – Loamy Upland, Saline 7"-10" p.z.
Soils silty to clayey with salic or natric horizon (<12")
R040XB223AZ – Clayey Upland, Saline 7"-10" p.z.
R040XB223AZ – Clayey Upland, Saline 7"-10" p.z.
Gently sloping terrain (slopes predominantly ≤ 15%)
Steeply sloping terrain (slopes predominantly >15%)
Soil surface armored with interlocking rock fragments, 1-3" vesicular horizon
R040XB230AZ – Desert Pavement 7"-10" p.z.
R040XB230AZ – Desert Pavement 7"-10" p.z.
Soil surface without interlocking rock fragments
Soils shallow (≤20" depth)
Soils moderately deep to deep (>20" depth)
Soils calcareous
R040XB210AZ – Limy Upland 7"-10" p.z.
R040XB210AZ – Limy Upland 7"-10" p.z.
Soils non-calcareous
R040XB220AZ – Granitic Upland 7"-10" p.z.
R040XB220AZ – Granitic Upland 7"-10" p.z.
Soils calcareous
Soils non-calcareous
Soils skeletal
R040XB208AZ – Limy Upland, Deep 7"-10" p.z.
R040XB208AZ – Limy Upland, Deep 7"-10" p.z.
Soils not skeletal
Soils loamy, not gypsic
R040XB207AZ – Limy Fan 7"-10" p.z.
R040XB207AZ – Limy Fan 7"-10" p.z.
Soils loamy and gypsic
R040XB234AZ – Limy Fan, Gypsum 7" -10" p.z.
R040XB234AZ – Limy Fan, Gypsum 7" -10" p.z.
Soils with an argillic (or clay cambic) horizon
Soils without an argillic horizon
Soils with sandy loam surface ≥4" depth
R040XB218AZ – Sandy Loam Upland 7"-10" p.z.
R040XB218AZ – Sandy Loam Upland 7"-10" p.z.
Soils with loam surface (any depth) OR sandy loam surface <4" depth
R040XB213AZ – Loamy Upland 7"-10" p.z.
R040XB213AZ – Loamy Upland 7"-10" p.z.
Soils with clay loam surface (not vertic)
R040XB205AZ – Clay Loam Upland 7"-10" p.z.
R040XB205AZ – Clay Loam Upland 7"-10" p.z.
Soils with clayey surface (vertic)
R040XB204AZ – Clayey Upland 7"-10" p.z.
R040XB204AZ – Clayey Upland 7"-10" p.z.
Soils sandy, eolian
R040XB217AZ – Sandy Upland 7"-10" p.z.
R040XB217AZ – Sandy Upland 7"-10" p.z.
Soils loamy fine sand to sandy loam, alluvial
R040XB221AZ – Sandy Loam, Deep 7"-10" p.z.
R040XB221AZ – Sandy Loam, Deep 7"-10" p.z.
Soils shallow (≤20" depth)
Soils moderately deep to deep (>20" depth)
Soils calcareous
Soils non-calcareous in upper 10 inches
Surface fragments black or nearly so (Munsell color value <4)
R040XB201AZ – Basalt Hills 7"-10" p.z.
R040XB201AZ – Basalt Hills 7"-10" p.z.
Surface fragments not black (Munsell color value ≥4)
Parent material weathered/fractured (can dig into with shovel)
R040XB202AZ – Paralithic Hills 7"-10" p.z.
R040XB202AZ – Paralithic Hills 7"-10" p.z.
Parent material indurated (cannot dig into with shovel)
R040XB231AZ – Lithic Hills 7"-10" p.z.
R040XB231AZ – Lithic Hills 7"-10" p.z.
Parent material weathered/fractured (can dig into with shovel)
R040XB206AZ – Shallow Hills 7"-10" p.z.
R040XB206AZ – Shallow Hills 7"-10" p.z.
Parent material indurated (cannot dig into with shovel)
R040XB222AZ – Volcanic Hills 7"-10" p.z.
R040XB222AZ – Volcanic Hills 7"-10" p.z.
Soils fine sand, eolian
R040XB232AZ – Sandy Slopes, Dunes 7"-10" p.z.
R040XB232AZ – Sandy Slopes, Dunes 7"-10" p.z.
Soils calcareous, not gypsic
R040XB209AZ – Limy Slopes 7"-10" p.z.
R040XB209AZ – Limy Slopes 7"-10" p.z.
Soils calcareous and gypsic
R040XB233AZ – Limy Slopes, Gypsum 7"-10" p.z.
R040XB233AZ – Limy Slopes, Gypsum 7"-10" p.z.
Soils non-calcareous in the upper 10 inches
R040XB212AZ – Loamy Slopes 7"-10" p.z.
R040XB212AZ – Loamy Slopes 7"-10" p.z.
Slightly to strongly saline soils (ECe ≥4 dS/m)
Non-saline to very slightly saline soils (ECe <4 dS/m)
Soils with a high water table
R040XC315AZ – Saline Bottom 3"-7" p.z.
R040XC315AZ – Saline Bottom 3"-7" p.z.
Soils without a high water table
R040XC314AZ – Saline Swale 3"-7" p.z.
R040XC314AZ – Saline Swale 3"-7" p.z.
Soils with water table available to plant community
Soils without water table available to plant community
Soils with a reduced matrix
R040XC331AZ – Sandy Bottom, Ciénaga 3"-7" p.z.
R040XC331AZ – Sandy Bottom, Ciénaga 3"-7" p.z.
Soils with visible reduction-oxidation features
F040XC327AZ – Sandy Bottom, Woodland 3"-7" p.z.
F040XC327AZ – Sandy Bottom, Woodland 3"-7" p.z.
Soils without visible reduction-oxidation features
F040XC328AZ – Loamy Bottom, Woodland 3"-7" p.z.
F040XC328AZ – Loamy Bottom, Woodland 3"-7" p.z.
Narrow drainage, active flow channel <5' width
R040XC330AZ – Sandy Loam Drainage 3"-7" p.z.
R040XC330AZ – Sandy Loam Drainage 3"-7" p.z.
Wide drainage, active flow channel >5' width
Soils sandy
R040XC318AZ – Sandy Wash 3"-7" p.z.
R040XC318AZ – Sandy Wash 3"-7" p.z.
Soils fine sandy loam to clay loam
R040XC312AZ – Loamy Swale 3"-7" p.z.
R040XC312AZ – Loamy Swale 3"-7" p.z.
Soils clayey
R040XC303AZ – Clayey Swale 3"-7" p.z.
R040XC303AZ – Clayey Swale 3"-7" p.z.
Gently sloping terrain (slopes <15%)
Steeply sloping terrain (slopes >15%)
Soil surface armored with interlocking rock fragments, well-developed vesicular surface horizon
R040XC326AZ – Desert Pavement 3"-7" p.z.
R040XC326AZ – Desert Pavement 3"-7" p.z.
Soil surface not armored with interlocking rock fragments, soil surface horizon lacking vesicular crust
Soils shallow (≤20" depth)
Soils moderately deep to deep (>20" depth)
Soils calcareous
R040XC310AZ – Limy Upland 3"-7" p.z.
R040XC310AZ – Limy Upland 3"-7" p.z.
Soils non-calcareous
R040XC322AZ – Shallow Upland 3"-7" p.z.
R040XC322AZ – Shallow Upland 3"-7" p.z.
Soils moderately saline to strongly saline (EC >8 dS/m)
R040XC317AZ – Saline Upland 3"-7" p.z.
R040XC317AZ – Saline Upland 3"-7" p.z.
Soils non-saline to slightly saline (EC ≤8 dS/m)
Soil calcareous
Soil non-calcareous in upper 10 inches
Soil skeletal
R040XC311AZ – Limy Upland, Deep 3"-7" p.z.
R040XC311AZ – Limy Upland, Deep 3"-7" p.z.
Soil not skeletal
Soil sandy, eolian
R040XC307AZ – Limy Fan, Sandy 3"-7" p.z.
R040XC307AZ – Limy Fan, Sandy 3"-7" p.z.
Soil loamy, slopes 0-6%
R040XC306AZ – Limy Fan 3"-7" p.z.
R040XC306AZ – Limy Fan 3"-7" p.z.
Soil loamy, slopes >7%
R040XC302AZ – Limy Slopes 3"-7" p.z.
R040XC302AZ – Limy Slopes 3"-7" p.z.
Soil gypsic, slopes >7%
R040XC309AZ – Limy Slopes, Gypsum 3"-7" p.z.
R040XC309AZ – Limy Slopes, Gypsum 3"-7" p.z.
Argillic horizon present
R040XC320AZ – Sandy Loam Upland 3"-7" p.z.
R040XC320AZ – Sandy Loam Upland 3"-7" p.z.
No argillic horizon, soil eolian
R040XC319AZ – Sandy Upland 3"-7" p.z.
R040XC319AZ – Sandy Upland 3"-7" p.z.
Soils shallow, calcareous (≤20" depth)
Soils moderately deep to deep, calcareous (>20" depth)
Surface fragments black or nearly so (Munsell color value <4)
R040XC301AZ – Basalt Hills 3"-7" p.z.
R040XC301AZ – Basalt Hills 3"-7" p.z.
Surface fragments not black (Munsell color value ≥4)
Parent material fractured or weather, able to dig into with shovel
R040XC305AZ – Paralithic Hills 3"-7" p.z.
R040XC305AZ – Paralithic Hills 3"-7" p.z.
Parent material indurated for not weathered, unable to dig into with shovel
R040XC324AZ – Lithic Hills 3"-7" p.z.
R040XC324AZ – Lithic Hills 3"-7" p.z.
Soils fine sandy, eolian
R040XC329AZ – Sandy Slopes, Dunes 3"-7" p.z.
R040XC329AZ – Sandy Slopes, Dunes 3"-7" p.z.
Soils loamy, alluvial
R040XC302AZ – Limy Slopes 3"-7" p.z.
R040XC302AZ – Limy Slopes 3"-7" p.z.
Soils gypsic
R040XC309AZ – Limy Slopes, Gypsum 3"-7" p.z.
R040XC309AZ – Limy Slopes, Gypsum 3"-7" p.z.
Soils with water table available to the plant community
Soils without a water table available to the plant community
Soils with visible reduction-oxidation features
R040XA125AZ – Sandy Bottom, Woodland 10"-13" p.z.
R040XA125AZ – Sandy Bottom, Woodland 10"-13" p.z.
Soils without visible reduction-oxidation features
R040XA124AZ – Loamy Bottom, Woodland 10"-13" p.z.
R040XA124AZ – Loamy Bottom, Woodland 10"-13" p.z.
Soils sandy
R040XA115AZ – Sandy Wash 10"-13" p.z.
R040XA115AZ – Sandy Wash 10"-13" p.z.
Soils fine sandy loam to clay loam
R040XA112AZ – Loamy Swale 10"-13" p.z.
R040XA112AZ – Loamy Swale 10"-13" p.z.
Soils clayey
R040XA102AZ – Clayey Swale 10"-13" p.z.
R040XA102AZ – Clayey Swale 10"-13" p.z.
Gently sloping terrain (slopes predominantly <15%)
Steeply sloping terrain (slopes predominantly ≥15%)
Soils shallow (≤20 inches)
Soils moderately deep to deep (>20 inches)
Soils calcareous
R040XA111AZ – Limy Upland 10"-13" p.z.
R040XA111AZ – Limy Upland 10"-13" p.z.
Soils non-calcareous
R040XA121AZ – Granitic Upland 10"-13" p.z.
R040XA121AZ – Granitic Upland 10"-13" p.z.
Soils calcareous in the upper 10" or throughout
Soils non-calcareous in the upper 10 inches
Soils gypsic
R040XA126AZ – Gypsum Upland 10"-13" p.z.
R040XA126AZ – Gypsum Upland 10"-13" p.z.
Soils not gypsic
Soils with argillic horizon (or clay cambic)
R040XA130AZ – Loamy Upland, Limy 10"-13" p.z.
R040XA130AZ – Loamy Upland, Limy 10"-13" p.z.
Soils skeletal (≥35% fragments)
R040XA106AZ – Limy Upland, Deep 10"-13" p.z.
R040XA106AZ – Limy Upland, Deep 10"-13" p.z.
Soils not skeletal (<35% fragments) and without argillic
R040XA108AZ – Limy Fan 10"-13" p.z.
R040XA108AZ – Limy Fan 10"-13" p.z.
Soils without an argillic horizon
Soils with an argillic horizon
Soils sandy and eolian
R040XA116AZ – Sandy Upland 10"-13" p.z.
R040XA116AZ – Sandy Upland 10"-13" p.z.
Soils loamy fine sand to sandy loam
R040XA117AZ – Sandy Loam Upland, Deep 10"-13" p.z.
R040XA117AZ – Sandy Loam Upland, Deep 10"-13" p.z.
Soils with sandy loam surface ≥4" over argillic
R040XA118AZ – Sandy Loam Upland 10"-13" p.z.
R040XA118AZ – Sandy Loam Upland 10"-13" p.z.
Soils with sandy loam surface <4" or loam surface any depth over argillic
R040XA114AZ – Loamy Upland 10"-13" p.z.
R040XA114AZ – Loamy Upland 10"-13" p.z.
Soils with a clayey surface, not vertic
R040XA120AZ – Clay Loam Upland 10"-13" p.z.
R040XA120AZ – Clay Loam Upland 10"-13" p.z.
Soils with a clayey surface, vertic
R040XA104AZ – Clayey Upland 10"-13" p.z.
R040XA104AZ – Clayey Upland 10"-13" p.z.
Soils shallow (≤20 inches)
Soils moderately deep to deep (>20 inches)
Soils calcareous throughout
Soils non-calcareous in upper 10 inches
Soils over limestone parent materials
R040XA107AZ – Limestone Hills 10"-13" p.z.
R040XA107AZ – Limestone Hills 10"-13" p.z.
Soils over fanglomerate and conglomerate
R040XA128AZ – Conglomerate Hills 10"-13" p.z.
R040XA128AZ – Conglomerate Hills 10"-13" p.z.
Soils over basalt parent materials
R040XA101AZ – Basalt Hills 10"-13" p.z.
R040XA101AZ – Basalt Hills 10"-13" p.z.
Soils over volcanic rock, breccia, and agglomerates
R040XA129AZ – Limy Hills 10"-13" p.z.
R040XA129AZ – Limy Hills 10"-13" p.z.
Soils over granite, gneiss, schist, rhyolite
R040XA105AZ – Shallow Hills 10"-13" p.z.
R040XA105AZ – Shallow Hills 10"-13" p.z.
Soils over andesite, dacite, basalt, welded tuff
R040XA123AZ – Volcanic Hills 10"-13" P.Z.
R040XA123AZ – Volcanic Hills 10"-13" P.Z.
Soils over schist
R040XA119AZ – Schist Hills 10"-13" p.z.
R040XA119AZ – Schist Hills 10"-13" p.z.
Soils calcareous throughout
Soils non-calcareous in the upper 10 inches
Soils gypsic
R040XA127AZ – Gypsum Slopes 10"-13" p.z.
R040XA127AZ – Gypsum Slopes 10"-13" p.z.
Soils not gypsic
R040XA110AZ – Limy Slopes 10"-13" p.z.
R040XA110AZ – Limy Slopes 10"-13" p.z.
Soils sandy loam to clay loam
R040XA113AZ – Loamy Slopes 10"-13" p.z.
R040XA113AZ – Loamy Slopes 10"-13" p.z.
Soils clay loam to clay
R040XA103AZ – Clayey Slopes 10"-13" p.z.
R040XA103AZ – Clayey Slopes 10"-13" p.z.
Site occurs on the basin floor.
Site occurs on any part of a hill and/or hillslope
Site occurs on any type or part of alluvial fan (e.g. inset fan, fan remanent, ballena, fan apron etc.)
Site occurs within a confined and/or semi-confined channel, avulsion rare to frequent
Site occurs on sand dunes or sandsheets
The site occurs on well-drained, moderately rapidly permeable soils in lacustrine basins and large floodplains. Slopes are gently sloping to nearly level. Elevation ranges from 230 feet below sea level to 800 feet above.
Surface fragments, including rock outcrop, over 3 inches in diameter cover greater than 15% of the soil surface
8’ Surface fragments over 3 inches in diameter cover less than 15% of the soil surface
Less than 15% slope; pediment: Please refer to R030XY023CA Hyperthermic Dissected Shallow Pediment.
Greater than 15% slope.
. Generally greater than 15% cover of fragments over 10 inches diameter; non-northerly aspects
Generally less than 15% cover of fragments over 10 inches diameter; northerly aspects
Colluvium/residuum from plutonic and plutonic metamorphosed
Alluvial fan with no water flow patterns; fluvial processes are no longer evident due to fan abandonment
Active alluvial fans with water flow patterns
Desert pavement, all ages; vesicular pores in the soil surface horizon reduce moisture infiltration as well as severely limit plant germination and establishment
Not a desert pavement or dissimilar enough to allow more moisture infiltration and plant establishment, if a vesicular horizon is present it is very thin and weak and if uneven surface fragements are present, they may assist with moisture infiltration
Surface fragments over 3 inches in diameter cover greater than 15% of the soil surface. Elevation above 1650 ft (500m) elevation
Surface fragments over 3 inches in diameter cover less than 15% of the soil surface
Surface fragments over 3 inches in diameter cover greater than 15% of the soil surface. Elevation below 1650 ft (500m) elevation
Surface fragments over 3 inches in diameter cover greater than 15% of the soil surface with cobbles being the predominent size.
Greater water flow patterns, and small drainages due to run-off from higher areas.
Less water flow patterns with very occasional runoff and presence of brittlebush.
The site occurs primarily on fan piedmonts but can also be found in some minor drainageways. Receiving slightly higher run-off and/or rainfall than other creosotebush-white bursage communities, it is a higher producing site.
Small drainages order 3 or smaller draining the convex summit position of alluvial fans.
Landscape shape is concave which concentrates sheetflow as an ephemeral stream.
Braided stream
Stream confined to the extent that braided channels do not exist, usually between fan remnants in the upper piedmont slopes
Sandy soils with loose single grain surface structure
Sandy skletal and/or massive surface structure
Sandy skletal and/or massive surface structure with stones on the surface. Blue paloverde is dominant
Wash drains desert pavement landforms
Wash does not drain desert pavement landforms
Drains desert pavement with argillic and/or calcic pr petrocalcic horizon.
Drains sandstone material; steeper (greater than 4% slope) less infiltration
Drains plutonic and plutonic metamorphosed material such as schist, lower sloping with greater infiltration
This ecological site is found on sand sheets, coppice dunes, and semi-stabilized dunes.
[Criteria]
Long term average mean annual precipitation
- No filter
- 0 – 10cm (0 – 4in)
- 10 – 15cm (4 – 6in)
- 15 – 20cm (6 – 8in)
- 20 – 25cm (8 – 10in)
- 25 – 30cm (10 – 12in)
- 30 – 35cm (12 – 14in)
—
cm
Long term average frost free days
- No filter
- 250 – 270days
- 270 – 290days
- 290 – 310days
- 310 – 330days
- 330 – 350days
- 350 – 366days
—
days
- No filter
- 0 – 200m (0 – 700ft)
- 200 – 400m (700 – 1300ft)
- 400 – 600m (1300 – 2000ft)
- 600 – 800m (2000 – 2600ft)
- 800 – 1000m (2600 – 3300ft)
- 1000 – 1200m (3300 – 3900ft)
- 1200 – 1400m (3900 – 4600ft)
—
m
- No filter
- 0 – 3%
- 3 – 5%
- 5 – 10%
- 10 – 15%
- 15 – 20%
- 20 – 25%
- 25 – 30%
- 30 – 35%
- 35 – 40%
- 40 – 45%
- 45 – 50%
- 50 – 60%
- 60 – 70%
- 70 – 80%
—
%
- No filter
- Alluvial fan
- Alluvial flat
- Ballena
- Basin floor
- Channel
- Drainageway
- Dune
- Dune field
- Fan
- Fan apron
- Fan piedmont
- Fan remnant
- Flood plain
- Hill
- Inset fan
- Interfluve
- Lake plain
- Lakebed
- Lakeshore
- Mesa
- Mountain
- Mountain slope
- Pediment
- Ridge
- Sand sheet
- Stream terrace
- Swale
- Terrace
- Wash
- No filter
- Andesite
- Basalt
- Conglomerate, unspecified
- Diabase
- Gneiss
- Granite
- Igneous and metamorphic
- Igneous, metamorphic and sedimentary
- Rhyolite
- Volcanic breccia, basic
- Volcanic breccia, unspecified
- No filter
- Alluvium
- Colluvium
- Eolian sands
- Lacustrine deposits
- Residuum
- Slope alluvium
Soil surface texture
- No filter
- Clay
- Clay loam
- Coarse sand
- Coarse sandy loam
- Fine sand
- Fine sandy loam
- Loam
- Loamy coarse sand
- Loamy fine sand
- Loamy sand
- Sand
- Sandy clay
- Silty clay loam
- Silt loam
- Sandy loam
- Very fine sand
- Very fine sandy loam
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Ecological site keys
MLRA 40-2 Ecological Sites
I.
Bottom position (plant community reliant upon run-on from valley-side or over-bank)
B
Non-saline to very slightly saline soils (ECe < 4 dS/m)
1
Soils with water table available to plant community
i.
Soils with visible reduction-oxidation features
... F040XB215AZ – Sandy Bottom, Woodland 7" - 10" p.z.
2
Soils without a water table available to the plant community
ii.
Wide drainage, active flow path >4' width
II.
Upland position (plant community reliant upon on-site precipitation, run-on ≤ run-off)
A.
Slightly to strongly saline soils (ECe ≥ 4 dS/m)
4
Soils silty to clayey with salic or natric horizon (<12")
... R040XB223AZ – Clayey Upland, Saline 7"-10" p.z.
B.
Non-saline to very slightly saline soils (ECe < 4 dS/m)
1
Gently sloping terrain (slopes predominantly ≤ 15%)
i.
Soil surface armored with interlocking rock fragments, 1-3" vesicular horizon
... R040XB230AZ – Desert Pavement 7"-10" p.z.
ii.
Soil surface without interlocking rock fragments
a.
Soils shallow (≤20" depth)
b.
Soils moderately deep to deep (>20" depth)
1)
Soils calcareous
b)
Soils not skeletal
2)
Soils non-calcareous
a)
Soils with an argillic (or clay cambic) horizon
(2)
Soils with loam surface (any depth) OR sandy loam surface <4" depth
... R040XB213AZ – Loamy Upland 7"-10" p.z.
b)
Soils without an argillic horizon
2
Steeply sloping terrain (slopes predominantly >15%)
i.
Soils shallow (≤20" depth)
a.
Soils calcareous
1)
Surface fragments black or nearly so (Munsell color value <4)
... R040XB201AZ – Basalt Hills 7"-10" p.z.
2)
Surface fragments not black (Munsell color value ≥4)
a)
Parent material weathered/fractured (can dig into with shovel)
... R040XB202AZ – Paralithic Hills 7"-10" p.z.
b)
Parent material indurated (cannot dig into with shovel)
... R040XB231AZ – Lithic Hills 7"-10" p.z.
b.
Soils non-calcareous in upper 10 inches
1)
Parent material weathered/fractured (can dig into with shovel)
... R040XB206AZ – Shallow Hills 7"-10" p.z.
2)
Parent material indurated (cannot dig into with shovel)
... R040XB222AZ – Volcanic Hills 7"-10" p.z.
ii.
Soils moderately deep to deep (>20" depth)
MLRA 40-3 Ecological Sites
I.
Bottom position (plant community reliant upon run-on from valley-side or over-bank)
A.
Slightly to strongly saline soils (ECe ≥4 dS/m)
B.
Non-saline to very slightly saline soils (ECe <4 dS/m)
1
Soils with water table available to plant community
ii.
Soils with visible reduction-oxidation features
... F040XC327AZ – Sandy Bottom, Woodland 3"-7" p.z.
iii.
Soils without visible reduction-oxidation features
... F040XC328AZ – Loamy Bottom, Woodland 3"-7" p.z.
2
Soils without water table available to plant community
ii.
Wide drainage, active flow channel >5' width
II.
Upland position (plant community reliant upon on-site precipitation, run-on ≤ run-off)
A.
Gently sloping terrain (slopes <15%)
1
Soil surface armored with interlocking rock fragments, well-developed vesicular surface horizon
... R040XC326AZ – Desert Pavement 3"-7" p.z.
2
Soil surface not armored with interlocking rock fragments, soil surface horizon lacking vesicular crust
i.
Soils shallow (≤20" depth)
ii.
Soils moderately deep to deep (>20" depth)
a.
Soils moderately saline to strongly saline (EC >8 dS/m)
... R040XC317AZ – Saline Upland 3"-7" p.z.
b.
Soils non-saline to slightly saline (EC ≤8 dS/m)
1)
Soil calcareous
b)
Soil not skeletal
2)
Soil non-calcareous in upper 10 inches
B.
Steeply sloping terrain (slopes >15%)
1
Soils shallow, calcareous (≤20" depth)
i.
Surface fragments black or nearly so (Munsell color value <4)
... R040XC301AZ – Basalt Hills 3"-7" p.z.
ii.
Surface fragments not black (Munsell color value ≥4)
a.
Parent material fractured or weather, able to dig into with shovel
... R040XC305AZ – Paralithic Hills 3"-7" p.z.
b.
Parent material indurated for not weathered, unable to dig into with shovel
... R040XC324AZ – Lithic Hills 3"-7" p.z.
2
Soils moderately deep to deep, calcareous (>20" depth)
MLRA 40-1 Ecological Sites
I.
Bottom position (plant community reliant upon run-on from valley-side or over-bank)
A.
Soils with water table available to the plant community
1
Soils with visible reduction-oxidation features
... R040XA125AZ – Sandy Bottom, Woodland 10"-13" p.z.
2
Soils without visible reduction-oxidation features
... R040XA124AZ – Loamy Bottom, Woodland 10"-13" p.z.
B.
Soils without a water table available to the plant community
II.
Upland position (plant community reliant upon on-site precipitation, run-on ≤ run-off)
A.
Gently sloping terrain (slopes predominantly <15%)
1
Soils shallow (≤20 inches)
2
Soils moderately deep to deep (>20 inches)
i.
Soils calcareous in the upper 10" or throughout
b.
Soils not gypsic
ii.
Soils non-calcareous in the upper 10 inches
a.
Soils without an argillic horizon
b.
Soils with an argillic horizon
2)
Soils with sandy loam surface <4" or loam surface any depth over argillic
... R040XA114AZ – Loamy Upland 10"-13" p.z.
B.
Steeply sloping terrain (slopes predominantly ≥15%)
1
Soils shallow (≤20 inches)
i.
Soils calcareous throughout
ii.
Soils non-calcareous in upper 10 inches
2
Soils moderately deep to deep (>20 inches)
i.
Soils calcareous throughout
ii.
Soils non-calcareous in the upper 10 inches
DRAFT LRU Key
I.
Broad visual assessment of uplands with slopes <15%. Desert pavement present, elevations <2,000' above sea level
A.
Leguminous trees present in all washes and drainages; generally absent from uplands between them
B.
Leguminous trees ONLY present in largest washes
II.
Broad visual assessment of uplands with slopes <15%. Desert pavement absent; elevations generally >2,000' above sea level
MLRA 31
I.
Site occurs on the basin floor.
A.
The site occurs on well-drained, moderately rapidly permeable soils in lacustrine basins and large floodplains. Slopes are gently sloping to nearly level. Elevation ranges from 230 feet below sea level to 800 feet above.
III.
Site occurs on any part of a hill and/or hillslope
A.
Surface fragments, including rock outcrop, over 3 inches in diameter cover greater than 15% of the soil surface
1
Less than 15% slope; pediment: Please refer to R030XY023CA Hyperthermic Dissected Shallow Pediment.
2
Greater than 15% slope.
i.
. Generally greater than 15% cover of fragments over 10 inches diameter; non-northerly aspects
ii.
Generally less than 15% cover of fragments over 10 inches diameter; northerly aspects
iii.
Colluvium/residuum from plutonic and plutonic metamorphosed
B.
8’ Surface fragments over 3 inches in diameter cover less than 15% of the soil surface
IV.
Site occurs on any type or part of alluvial fan (e.g. inset fan, fan remanent, ballena, fan apron etc.)
A.
Alluvial fan with no water flow patterns; fluvial processes are no longer evident due to fan abandonment
1
Desert pavement, all ages; vesicular pores in the soil surface horizon reduce moisture infiltration as well as severely limit plant germination and establishment
2
Not a desert pavement or dissimilar enough to allow more moisture infiltration and plant establishment, if a vesicular horizon is present it is very thin and weak and if uneven surface fragements are present, they may assist with moisture infiltration
iii.
Surface fragments over 3 inches in diameter cover greater than 15% of the soil surface. Elevation above 1650 ft (500m) elevation
iii.
Surface fragments over 3 inches in diameter cover less than 15% of the soil surface
iv.
Surface fragments over 3 inches in diameter cover greater than 15% of the soil surface. Elevation below 1650 ft (500m) elevation
v.
Surface fragments over 3 inches in diameter cover greater than 15% of the soil surface with cobbles being the predominent size.
B.
Active alluvial fans with water flow patterns
1
Greater water flow patterns, and small drainages due to run-off from higher areas.
2
Less water flow patterns with very occasional runoff and presence of brittlebush.
3
The site occurs primarily on fan piedmonts but can also be found in some minor drainageways. Receiving slightly higher run-off and/or rainfall than other creosotebush-white bursage communities, it is a higher producing site.
V.
Site occurs within a confined and/or semi-confined channel, avulsion rare to frequent
A.
Small drainages order 3 or smaller draining the convex summit position of alluvial fans.
F.
Landscape shape is concave which concentrates sheetflow as an ephemeral stream.
1
Braided stream
i.
Sandy soils with loose single grain surface structure
ii.
Sandy skletal and/or massive surface structure
iii.
Sandy skletal and/or massive surface structure with stones on the surface. Blue paloverde is dominant
2
Stream confined to the extent that braided channels do not exist, usually between fan remnants in the upper piedmont slopes
i.
Wash drains desert pavement landforms
ii.
Wash does not drain desert pavement landforms
a.
Drains sandstone material; steeper (greater than 4% slope) less infiltration
b.
Drains plutonic and plutonic metamorphosed material such as schist, lower sloping with greater infiltration
iii.
Drains desert pavement with argillic and/or calcic pr petrocalcic horizon.
VIII.
Site occurs on sand dunes or sandsheets
A.
This ecological site is found on sand sheets, coppice dunes, and semi-stabilized dunes.
[Label]
[Criteria]
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.
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