Description

MLRA is in Nevada (94 percent) and Oregon (6 percent). It makes up about 13,380 square miles (34,655 square kilometers). The area is characterized by a series of widely spaced, north-south-trending, uplifted fault-block mountain ranges that are separated by wide valleys filled with alluvium and lacustrine materials. Precipitation and elevation increase toward the extensive lava plateaus to the east and west. MLRA 24 has a gradual boundary with MLRAs 23, 25, and 27. The externally drained plateaus of MLRA 24 contrast with the internally drained plateaus and basins of MLRA 23. Directly to the east in MLRA 25, precipitation increases and mean annual temperature decreases, resulting in a shorter growing season and increased available soil moisture. To the southwest in MLRA 27, soil temperatures warm and elevations decrease, giving way to extensive playas, visible shorelines, and piedmont slopes dominated by Bailey’s greasewood.

Geographic subunits

Land Resource Unit 2. MLRA DX02402X - Lacustrine influenced basins and playas Topography: This LRU represents the lowest, driest part of the MLRA 24. Topography is dominated by basins floors and playas of the upper Lahontan Basin. Elevations are <1500m, with a median value of 1350m. This area generally flat, median slopes values are <2% and 95% of the area is <15%. Soil characteristics: Soils in this area are derived from lacustrine sediment, with a mesic soil temperature regime and typic aridic or aridic-xeric soil moisture regime. Soils are very deep and saline and/or sodic. Benchmark soils typical of MLRA 24 include, Boton Series, a Duric Torriorthent on lake plains and basin floors that formed in lacustrine sediments. Somewhat poorly drained Halaquepts (Wendane series) also occurs on basin floors that formed in alluvium on flood plains. Climate: The basin floors are warmer and dryer than the surrounding LRUs. Mean annual precipitation ranges from 226-506mm (8-22”) with a median value of 222mm (8.7”) (25th-75th% = 210-235mm), mean annual air temperature ranges from 9.1-10.34C (F). Evaporation exceeds precipitation for the entire area. Soil characteristics typically have a negative impact on infiltration further minimizing effective moisture. Biological Resources: Shadscale and bud sagebrush associated with Indian ricegrass and bottlebrush squirreltail are dominant on the drier sites. Black greasewood, basin wildrye are locally important on low terraces and flood plains. Winterfat is prevalent on very deep, fine textured soils.

Land Resource Unit 3. MLRA DX02403X – Peidmont slope Topography: This LRU is characterized by alluvial material of the basin and range. Topography is dominated by peidmont slope including alluvial fans and rock pediments. Elevations range from 1400-1900m, with a median value of 1600m. This area is not characterized by high relief, with the typical slope value being 10% or less, but may be as high as 45% in limited areas. Soil characteristics: Soils comprising this LRU formed in alluvium derived from mixed parent material, with a mesic soil temperature regime and an aridic bordering on xeric or xeric bordering on aridic soil moisture regime. Lower elevations areas of this LRU commonly have soils that have a typic aridic soil moisture regime. Haplocambids formed in loess over alluvium on lower alluvial fans and alluvial flats (Broyles and Weso series) and in alluvium on higher alluvial fans (Davey, Enko, and McConnel series). Shallow Argidurids formed in alluvium on fan remnants (Tumtum series) and in loess and alluvium on fan remnants and plateaus (Dewar series). Climate: Mean annual precipitation ranges from 228-342mm (8- 13”) with a median value 263mm (10”) (25th to 75th% =242-296mm), mean annual air temperature ranges from 8.66-10.47 C (47.5-50.8 F). Climate information in this section is derived from PRISM raster data, it should be considered an estimation and corrected when additional climate data is available. Evapotranspiration exceeds precipitation throughout the entire LRU. Biological Resources: This area supports shrub-grass vegetation. Shadscale is dominant at lower elevations of this LRU and big sagebrush and spiny hopsage are extensive on upper elevations. Indian ricegrass and needleandthread on common on sandy soils.

Land Resource Unit 5. MLRA DX02405X – Residuum/Colluvium hills and mountains Topography: This LRU represents the higher elevation mountainous portions of MLRA 24. It is characterized by hills and mountains and areas of high relief. Elevations are greater than 1900m. Slopes range from 8-65% with a median value of 40%. Soil characteristics: Soils primarily formed in residuum and/or colluvium. Soil temperatures range from mesic to frigid to cryic. Soil moisture is aridic bordering on xeric or xeric. Typical soils include moderately deep Haplargids (Roca series) formed in colluvium and residuum on hills and mountain slopes. Moderately deep Argixerolls (Reluctan series) formed in colluvium and residuum on hills, mountains, and plateaus. Benchmark soil series include Roca, a Xeric Halpargid on hills and mountains, formed in residuum and colluvium from volcanic rock and supports big sagebrush and bluebunch wheatgrass. Climate: Mean annual precipitation ranges from 12 to 21” (321-538mm), with a median value of 422mm (16”). Precipitation comes primarily in the forms of snow in the winterMean annual air temperature ranges from 4.9-9.45 C (40-49F). Evapotranspiration exceeds precipitation except at the upper elevations of this LRU. Biological Resources: Low sagebrush is common on soils shallow to a clay horizon. Black sagebrush and big sagebrush are also found throughout the area. Thurber needlegrass, bluebunch wheatgrass, basin wildrye, squirreltail, Sandberg bluegrass, forbs, and Douglas rabbitbrush are common associated plants. Idaho fescue and snowberry are locally important on sites where moisture is favorable and a limited amount Singleleaf pinyon and Utah juniper are found on high rocky areas.

Land Resource Unit 6. MLRA DX02406X – Dissected Lava Plateau Topography: This LRU is characterized by volcanic tablelands, uplifted plateaus, and dissected lava plains in the northern basin and range. Parts of this area was previously included in MLRA 23. Creation of this LRU will result in increased consistency in MLRA concepts across state boundaries, while continuing to recognize that this area is unique from the surrounding areas. Soil characteristics: Soils formed in loess influenced residuum and colluvium. Soil temperatures range from mesic to frigid and soil moisture ranges from aridic bordering on xeric to xeric. Depth to bedrock varies greatly with amount of deposition and/weathering. Soils of this MLRA range from shallow to very deep and are typically characterized by mollic epipedon at the higher elevations. Ochric epipedons are common at the lower limited of this LRU. Climate: mean annual precipitation ranges from <8” in the valleys and playas to more than 16” in the mountains and high elevation plateaus (220-420mm). Precipitation primarily comes as snow during the winter months. Summer thunder storms provide limited and inconsistent, but an important source of moisture Biological Resources: vegetation in this LRU is characterized by a mix of big sage brush (Artemisia tridentata) and bunchgrass. Higher precipitation zones typically support mountain big sagebrush (A. tridentata subsp vaseyana), Idaho fescue (Festuca idahoensis) and bluebunch wheatgrass (Pseudoridgeneria spicata). Lower elevation portions of this LRU support Wyoming big sagebrush (A. tridentata subsp wyomingensis), Indian ricegrass (Achnatherum hymenoides) and Thurber’s needlegrass (Achnatherum thurberania). Basin big sagerush (A. tridentata subsp tridentata) and western juniper (Juniperus occidentalis) can also be found scattered throughout the area.