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Draft. A draft ecological site description is either incomplete or has not undergone quality control and quality assurance review.
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous (1) Bromus hordeaceus
(2) Bromus diandrusPhysiographic features
This ecological site is found on nearly level to gently sloping valley floors from 0 to 9%, on all aspects at elevations ranging from 492 to 1640 feet.
Table 2. Representative physiographic features
Landforms (1) Valley flat
(2) Valley
(3) Flood plain
Elevation 492 – 1640 ft Slope 0 – 9 % Water table depth 0 – 59 in Aspect Aspect is not a significant factor Climatic features
The average annual precipitation in MLRA 15 is from 6 to 20 inches (150 to 510 millimeters) in the area south of San Francisco, and snowfall is rare. The north half of this area can be divided into two rainfall and snowfall zones. The southern half north of San Francisco has an average annual precipitation from 18 to 40 inches (460 to 1,015 millimeters) and snowfall is rare. In the north half, average annual precipitation is from 40 to 79 inches per year (1,015 to 2,010 millimeters) and snowfall is common. Precipitation is evenly distributed throughout fall, winter, and spring but is very low in summer. Coastal areas receive some moisture from fog in summer. Most of the rainfall occurs as low to moderate intensity, Pacific frontal storms during the winter from October to May. The average annual temperature is from 51 to 66 degrees F (10 to 19 degrees C), decreasing from south to north. The average frost-free period is 275 days (180 to 365 days), decreasing with elevation and from south to north.
At Pinnacles National Monument, the average annual precipitation is 17 inches with a range between 17 and 19 inches, mostly from rain in the winter months from November through April. The average annual air temperature is between 59 and 61 degrees Fahrenheit, and the frost-free period (>32F) is 190 to 210 days.
NOTE: Data collected for monthly precipitation and temperatures is only from one climate station.Table 3 Representative climatic features
Frost-free period (average) 210 days Freeze-free period (average) 0 days Precipitation total (average) 20 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
Water features are not a major factor influencing this ecological site. There are small inclusions within this ecological site, however, where water will flood fairly frequently for brief periods of time during the spring rains.
Soil features
This site is found on several parent materials, including granite, fanglomerate, volcanic and sedimentary rocks.
The soils (Elder & Still series) found on the stream terraces that no longer flood or have a seasonally high water table. They are alluvium derived from volcanic and sedimentary rocks, with the Elder soils giving way to coarse-grained textures and the Still series giving way to finer-grained textures.
The Elder soils are found closer to the stream channels and therefore are exposed to the swift moving floodwaters that are able to carry and deposit some of the heavier, sandy sediments. They are deep soils, with a dark sandy loam profile over stratified sandy loam to gravelly loamy coarse sand, and they are well-drained.Ecological dynamics
The reference state for this ecological site is dominated by purple needlegrass (Nassella pulchra) and blue wildrye (Elymus glaucus).
State and transition model
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 2 submodel, plant communities
State 1
Loamy floodplainsCommunity 1.1
Loamy floodplainsThis plant community is dominated by purple needlegrass, blue wildrye, creeping wildrye, california melicgrass, prairie junegrass, sedges, and rushes.
State 2
Invaded Loamy FloodplainsCommunity 2.1
Invaded Loamy FloodplainsThis plant community is invaded by exotic species that primarily consist of yellow starthistle (Centaurea solstitialis) and field mustard (Brassica rapa).
Additional community tables
Table 4. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 5. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Supporting information
Contributors
K. Moseley
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
Author(s)/participant(s) Contact for lead author Date Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Sub-dominant:
Other:
Additional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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Average percent litter cover (%) and depth ( in):
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Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
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Perennial plant reproductive capability:
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