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 a unique area within LRU L found on wave cut marine terraces that experience salty coastal winds and have eolian parent materials overtop of sandstone and are moderately to well drained.

Climate

The average annual precipitation in this MLRA is 23 to 98 inches (585 to 2,490 millimeters), increasing with elevation inland. Most of the rainfall occurs as low-intensity, Pacific frontal storms. Precipitation is evenly distributed throughout fall, winter, and spring, but summers are dry. Snowfall is rare along the coast, but snow accumulates at the higher elevations directly inland. Fog is a significant variable that defines this MLRA from other similar MLRAs. Summer fog frequency values of greater than 35% are strongly correlated to the extent of coast redwood distribution, which is a primary indicator species in this MLRA. Nightime fog is approximately twice as common as daytime fog and seasonally, it reaches its peak frequency in early August, with the greatest occurrence of fog from June through September (Johnstone and Dawson 2010). The average annual temperature is 49 to 59 degrees F (10 to 15 degrees C). The freeze-free period averages 300 days and ranges from 230 to 365 days, decreasing inland as elevation increases.

Soil features

This ESG covers the wide variety of eolian sand dominated marine terraces that are generally moderately to well drained, strongly acidic, with an effective rooting depth that ranges between less than 40 to greater than 60 inches.

Representative soils are Caspar, Quinliven, Gibwell, Gibney and Ferncreek, and the effective rooting depth is limited by saturation between the depths of less than 40 inches to greater than 60 inches for brief periods following episodes of heavy rain from December through April.

Vegetation dynamics

This ESG attempts to describe the basic understanding of the terraces of LRU L that have a significant eolian sand deposit overlying the sandstone and are within close proximity to the coastline, experiencing heavy, salt-laden coastal winds. This concept is primarily supported through literature and available information from the Mendocino County Survey . This concept occurs at lower elevations that spend long periods within summer coastal fog. This site is associated with both F004BL100CA and F004BL101CA but occurs in areas that are better drained. This has a significant impact on the vegetation composition and increases vegetation production relative to more poorly drained sites. Future work will need to be done to better understand the soil and site characteristics that drive the vegetation expression for this provisional ecological site concept.

Abiotic Factors

Vegetation expression appears to be strongly correlated to the effective rooting depth. Pinus muricata (Bishop pine), Sequoia sempervirens (coast redwood), Pseudotsuga menzeisii (Douglas-fir) and Notholithocarpus densiflorus (tanoak) dominated forests will be found on the soils with an effective rooting depth greater than 60 inches. While the Bishop pine and Arctostaphylos spp. (manzanita) forests dominate the soils with an effective rooting depth between 40 and 60 inches and the soils that have a saturated zone that starts between the depths of 24 and 48 inches and extends to a depth of more than 60 inches are typically the soils where Vaccinium ovatum (California huckleberry) becomes a more significant component of the understory with the Bishop pine and manzanita. Pinus muricata (Bishop pine) dominates younger, nutrient poor eolian sediments that are well drained and acidic.

The site is found at elevations below 1,000 feet between the ocean and the first main north-south ridge where frequent heavy summer fog is intercepted by a tree canopy. Soils have water available for plant growth most or all of the year, and average soil temperatures at a depth of 20 inches vary by less than 5 degrees C between summer and winter.

Primary Disturbances

The primary disturbance to this ecological site is urbanization and human developments that either de-water the site or completely obliterate it. Fire plays a prominent role in the life history and reproductive patterns of bishop pine, which is a prominent species in this ESG. Bishop pine is a serotinous, closed cone species, meaning some or all of its cones are locked shut until high heat loosens the resin coating the cones, unlocking seed chambers and allowing seed to be dispersed in large quantities following fire. Similar to other closed cone species, fires in bishop pine forests are often high intensity and stand replacing, though serotiny tends to be less pronounced in the northern portion of this species’ range (Cope, 1993). This fire relationship is suggestive of historic fire occurrence in this ESG, but the frequency of fire among the bishop pine in this area is unclear and not well studied. Historically, fires caused by a mix of lightning, tribal burning and early ranching were common in coastal mountains of northern California.

Citations

Cope, Amy B. 1993. Pinus muricata. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.usda.gov/database/feis/plants/tree/pinmur/all.html [2025, March 6].

Major Land Resource Area

MLRA 004B
Coastal Redwood Belt

Stage

Provisional