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

Hills with slopes range from 9-75% and elevations are from 20-1000 ft.

Climate

The average annual precipitation is 25-35 inches with annual average temperatures between 53-57 degrees F, and frost-free days from 300-365 days.

The Point Reyes/Farallon Islands LRU M includes the Point Reyes Peninsula, Bodega Head and the sand spit at the north end of Bodega Bay, and the offshore Farallon Islands. The maritime climate is temperate and humid, and fog often occurs. Heavy coastal winds are an influential factor in vegetation expression in this LRU that occur primarily in the summer months, explaining the large extent of coastal prairies and coastal scrub species along much of the coastline. Where trees are present along or near the coastline and within the reach of these heavy winds, the tree canopies form unidirectional windswept crowns.

Soil features

The soils for this ESG are moderately deep, strongly sloping to very steep, well drained soils underlain by sandstone and quartz-diorite. The representative soils are Kehoe soils with a very dark grayish brown loam surface and the Sheridan Variant soils that are brown coarse sandy loams over weathered quartz diorite.

Vegetation dynamics

This provisional ESG attempts to describe the bishop pine forests of this small LRU. Fragments of bishop pine forests exist along the coast of California where the climate, soil and fire regime are just right for their growth, and in LRU M, they exist primarily all along the northern end of Inverness Ridge. This concept lacks soil mapping and is therefore supported solely through literature and available information from Point Reyes National Seashore. This provisional ecological site concept covers a narrow range of bishop pine dynamics, however since there is no soils information for most of this LRU, 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

Pinus muricata (Bishop pine) forests are unique to granitic quartz-diorite soils. Although bishop pine can grow on a variety of soils, within MLRA 4B the soils are primarily old, shallow, acidic and poorly drained. Bishop pines prefer the cool, maritime climate that provides fog drip and sufficient summer moisture to mollify evapotranspiration rates in the summers, and low elevation slopes that are within 7-8 miles of the ocean.

Primary Disturbances

Fire plays a prominent role in the life history and reproductive patterns of bishop pine. 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. Stands are characteristically single-aged and originate after fires when the serotinous cones are opened (Cope, 1993). There is some research that suggests that bishop pine cones will also open during very hot days and disperse seeds. Depending on the fire intensity, some bishop pine can survive the fires, creating a more complex age-class distribution, however in most cases, fires will open wide areas by removing most all of the bishop pine and the seeds will germinate shortly after and grow rather rapidly post-fire. Although shrubs often fill in first after the fires in most bishop pine forests, the bishop pine does not seem to be affected and overtops the shrubs over time.

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

Contributors

Kendra Moseley