Natural Resources
Conservation Service
Ecological site R040XA125AZ
Sandy Bottom, Woodland 10"-13" p.z.
Last updated: 10/17/2024
Accessed: 11/21/2024
General information
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.
MLRA notes
Major Land Resource Area (MLRA): 040X–Sonoran Basin and Range
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.
LRU notes
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.
Classification relationships
USDA-NRCS Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin: Western Range and Irrigated Region D Major Land Resource Area 40 - Sonoran Basin and Range Land Resource Unit 1 - Upper Sonoran Desert Ecological Site Sandy Bottom, Woodland, 10"-13" p.z.
U.S. Environmental Protection Agency, Ecological Regions of North America: Level I, Region 10 North American Deserts Level II, 10.2 Warm Deserts Level III, Ecoregion 81, Sonoran Basin and Range Level IV, 81l, 81n, 81o
USDA-USFS Ecological Subregions: Sections of the Conterminous United States Section 322 American Semidesert and Desert Province Section 322B, Sonoran Desert
Ecological site concept
Sandy Bottom, Woodland, 10”–13” p.z. occurs on a bottom position, receiving both rainfall and run-on moisture. The shallow water table fluctuates in depth but is available to the plant community year-round. Soils have visible redoximorphic features with 80" of surface. Reference plant community is dominated by tall trees with a diverse understory. Obligate and facultative wetland plants occur along reaches of surface or near surface water flow. Aspect is a gallery woodland.
Associated sites
R040XA124AZ |
Loamy Bottom, Woodland 10"-13" p.z. adjacent stream terraces, no soil redox features |
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R040XA115AZ |
Sandy Wash 10"-13" p.z. stream channel with ephemeral water flows, no soil redox features |
Similar sites
F040XB215AZ |
Sandy Bottom, Woodland 7" - 10" p.z. Elevations 1,200' to 2,000' |
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F040XC327AZ |
Sandy Bottom, Woodland 3"-7" p.z. Elevations 300' to 1,200' |
Table 1. Dominant plant species
Tree |
(1) Populus fremontii |
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Shrub |
Not specified |
Herbaceous |
(1) Sporobolus wrightii |
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Ecosystem states
T1A | - | Groundwater pumping |
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T1C | - | Continuous heavy grazing |
R2A | - | Cessation of groundwater pumping. |
T2A | - | Salt cedar introduction |
R3A | - | Unknown |
R4A | - | Unknown |
T4A | - | Salt cedar introduction |