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Ecological Sections: Mono

Subsection 341Dm
Virginia - Pah Rah Ranges

This subsection comprises the Virginia Range south of the Truckee River and the Pah Rah Range north of the Truckee River.  The subsection is completely in Nevada and is included to complete the section.  It has a cold, semi-arid climate.  MLRA 26f.

Lithology and Stratigraphy.  Tertiary andesite, and possibly some dacite, flows and breccias predominate in the Virginia Range.  Tertiary basalt and andesite flows predominate in all but the northern part of the Pah Rah Range, where silicic ash-flow tuffs predominate.  Tertiary tuffaceous sedimentary rocks are common in both ranges and Quaternary andesite flows and breccias are common in the Virginia Range.  Small areas of Mesozoic granitic rocks and other kinds of Jurassic and Triassic rocks are present in both ranges.

Geomorphology.   Steep mountain slopes predominate in this subsection.  There are some volcanic plateaus, moderately steep hills, and gently to moderately sloping pediments and alluvial fans.  Some small closed basins occur on the volcanic plateaus.  The Truckee River flows on a narrow floodplain.  The mountains are aligned toward the northeast on the southeast side of the Virginia Range, toward the northwest at the north end of the Pah Rah Range, and north-south in the middle and on the west sides of the Ranges.  The elevation range is from about 4500 feet along the Truckee River to over 7600 feet on the ridge between Wakefield Peak and Orleans Hill in the Virginia Range and 8367 feet on Virginia Peak in the Pah Rah Mountains.  Mass wasting, fluvial erosion and deposition, and freeze-thaw are the main geomorphic processes.

Soils.  The soils are mostly Xerollic Haplargids and lesser amounts of Lithic Xerollic Haplargids, Torriorthentic Lithic and Aridic Pachic Haploxerolls, Aridic Pachic Argixerolls, and "bleached land."   The "bleached land" is soft, hydrothermally altered volcanic rock with little soil.  Small areas of Typic Chromoxererts occur on volcanic plateaus, on pediments, and in basins; and there are some Xerollic and shallow Palexerollic Durargids on alluvial fans.  Typic and Aquic Xerorthents occur on floodplain along the Truckee River.  The soils are well drained, except somewhat poorly drained soils along the Truckee River.  Soil temperature regimes are mostly frigid, with mesic along the Truckee River.  Soil moisture regimes are mostly aridic, bordering xeric, and some are xeric.

Vegetation.   The predominant natural plant communities are Big sagebrush series and, at higher elevations, Utah and Western juniper series.  Low sagebrush series is common on shallow soils, and Mixed chaparral shrublands are common on rocky and stony Haploxerolls and Argixerolls.  Singleleaf pinyon series occurs on Aridic Pachic Haploxerolls.  Jeffrey pine series occupies acid soils of "bleached land."  Shadscale series occurs on shallow Durargids with mesic soil temperature regimes.

Characteristic series by lifeform are not provided for this subsection.
Climate.  The mean annual precipitation is about 6 to 18 inches.  Much of the precipitation is snow.  Mean annual temperature is about 42 to 50 F.  The mean freeze-free period is in the range from 100 to 125 days.

Surface Water.  Runoff is rapid from the mountains and dissected volcanic plateaus, but there are some closed basins on volcanic plateaus.  Most of the runoff drains to the Truckee River or its tributaries.  The southern edge of the subsection is in the Carson River drainage basin and runoff from the northern part drains to Pyramid lake without passing through the Truckee River.  Streams in the mountains are dry most of each year, although the Truckee River is a permanent stream.  There is ephemeral ponding in some of the small closed basins, but there are no natural lakes in the subsection. 

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