Ecological site group description

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.

Physiography

This ESG is on hills and mountains at various elevations and slopes.

Climate

The average annual precipitation in MLRA 21 is typically 9 to 25 inches (241 to 635 millimeters). It is highest, up to 57 inches (1,450 millimeters), in small areas at high elevations on the western and southwestern edges of this MLRA. Other higher precipitation zones are in the scattered mountain ranges throughout the rest of this area. Most of the rainfall occurs as low- or moderate-intensity Pacific frontal storms during winter. At higher elevations, rain generally turns to snow. Snow may fall at lower elevations in winter but does not last. Summers are dry. The average annual temperature is 37 to 53 degrees F (3 to 12 degrees C). The average summer maximum temperature is 83 to 95 degrees F (28 to 35 degrees C). The average winter minimum temperature is 8 to 27 degrees F (-13 to -3 degrees C). The frost-free period is 70 to 185 days, with an average of 130 days.

Soil features

The soils for this ESG are primarily shallow, well drained soils formed in residuum and colluvium derived from volcanic rocks. Depth to bedrock is typically 10 to 20 inches (25 to 50 centimeters). Soils have low available water capacity (AWC) and slow permeability. Clay-rich soils yield much of their snowmelt as runoff, making them very important watershed areas. Soils with perched water tables in the spring cause poor aeration in the root zone of low sagebrush and play a significant role in the ecology of this ESG.

Some representative soils include Deven, Devada, and Orhood.

Vegetation dynamics

This ESG is dominated by broad-leaved evergreen shrubs 4 to 19 inches (0.1 to 0.5 meters) tall. Average shrub cover is typically 15 percent, but sometimes crowns touch. There may be deciduous shrubs and small trees sparsely scattered in some areas within this type. Grasses and forbs are typically sparse, providing 5 to 15 percent ground cover.

This habitat is dominated by either low sagebrush (often in association with yellow rabbitbrush or antelope bitterbrush) or big sagebrush. Western juniper may be sparsely scattered in stands dominated by low sagebrush. Common grass species include Sandberg bluegrass, bluebunch wheatgrass, squirreltail, Thurber’s needlegrass, and Idaho fescue. A rich variety of forbs is typically present. The abundance and distribution of associated plants are highly influenced by soils and precipitation.

This type commonly forms ecotones with sagebrush, pinyon-juniper, and juniper habitats in northeastern California. Thus, it may be difficult to determine the correct classification of some sites. For example, A. arbuscula communities are common as openings within coniferous forests on the Modoc Plateau. A. arbuscula communities may thus be found adjacent to mixed conifer, Jeffrey pine, or ponderosa pine forests. Climatic changes cause periodic shifts of ecotones, a relationship that is further complicated by invasion of coniferous woodlands into sagebrush habitats in response to fire suppression and grazing by domestic livestock.

Low sagebrush stands are "usually found on shallow soils with impaired drainage in the transition zone between the wetter bottom and open timber on the mountainsides". The type is also on terraces with hardpan or heavy clay soils. Where low sagebrush and antelope bitterbrush are mosaiced, low sagebrush grows on harsher sites (i.e., shallow, well-drained soils), and antelope bitterbrush grows on areas with deeper soils.

Information directly copied from:
California Wildlife Habitat Relationships System
California Department of Fish and Game
California Interagency Wildlife Task Group
By Jared Verner

Major Land Resource Area

MLRA 021X
Klamath and Shasta Valleys and Basins

Stage

Provisional