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 typically found in LRU I on rarely flooded, alluvial plains, low elevation mountains (under 200 feet), and flood plains across low slopes 0-5% and varied aspects within the areas of highest salt-spray impacts from the ocean and ocean storms. The sites are often on moist, uniform to slightly convex summits, shoulders, and backslopes of hills and debris slide areas. These hills are moderately steep to very steep and can tolerate the salty ocean spray of seaside dunes, headlands, and beaches, and the brackish water of bogs.

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, and 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. Nighttime 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 low mountains of the Northern Franciscan Redwood Forest LRU I, lie entirely within the coastal fog zone and are characteristically covered by fog-dependent coast redwoods and Douglas-fir. Historically, unbroken redwood forests occurred and moderated local climate by trapping coastal fog and producing shade. The combination of shade, root competition, young soils with a deep organic debris layer on the soil surface, occasional fire, and silting by floods limits the number of plant species that occur here. The region extends north only about 10 miles into Oregon near Brookings. Dominated by conifers, the region also includes Sitka spruce, western hemlock, western redcedar, Port Orford cedar, and grand fir. Hardwoods such as red alder, Pacific rhododendron, and tanoak commonly occur. This LRU also includes the areas known as the Bald Hills that have been maintained for over 100 years as prairies and oak woodlands through prescribed fire. These hills are dominated by Oregon white oak and perennial and annual native and non-native grasses and forbs but are actively encroached by Douglas-fir and redwood. Fine and fine-loamy, udic, isomesic, Ultisols and Alfisols are typical.

Picea sitchensis (Sitka spruce) forests are unique in this MLRA in their ability to dominate the stabilized younger sediments along the coastline that are heavily impacted by the coastal winds, winter storms, and significant sea salt spray. Sitka spruce is limited to areas of high annual precipitation, 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 5-6 miles of the ocean.

Soil features

Soils are variable, but will be dominated by fine-loamy or fine-silty textures in alluvium derived from mixed sources. They are found primarily within the Entisols and Inceptisols families, that are either oxyaquic or fluventic and slightly saline. They will generally have water at depths from 0-55 inches, and range from moderately well to poorly drained and rarely experience flooding events.

Representative soils include Ferndale and Canalschool.

Vegetation dynamics

This provisional ecological site concept attempts to describe the Picea sitchensis (Sitka spruce) dominated forests of LRU I. Fragments of Sitka spruce forests exist along the North Coast of California where the climate and soils are just right for their growth, however LRU I is the most dominant portion of the southern distribution of Sitka spruce, existing primarily along the lowest marine terraces and upper stream terraces closest to the coastline before coast redwoods dominate the overstory.

This concept is primarily supported through literature and available information from Redwood National Park Soil Survey. This provisional ecological site group covers the stabilized, yet fluventic soils close to the coastline that are most impacted by sea salt spray, 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.

Primary Disturbances

Sitka spruce ecological site has evolved with a low natural disturbance regime in coastal areas with a fog influence. Its close proximity to the coastal zone has caused the site to evolve with small to moderate disturbances from wind events. This is the primary disturbance to these Sitka spruce forests. Windthrow can account for up to 80 percent of the mortality within stands. Regeneration from gap phase replacement, however, is rapid (Griffiths, 1992). Winter winds from the northwest can be extreme and repeated disturbance by wind is evidenced by a hummocky ground appearance caused by fallen trees and root wads (Agee, 1993). Rarely, more severe wind events could lead to larger amounts of windthrow. Alnus rubra (red alder) will often establish dominance in these openings that are created during these wind events that open the canopy and knock down the Sitka spruce trees.

Small disturbance events that leave wind-created openings are likely to favor the establishment of shade-tolerant species including: Sitka spruce, Tsuga heterophyllia (western hemlock) and in rare cases, Sequoia sempervirens (coast redwood). Colonization of areas by Sitka spruce or red alder may occur in areas subject to debris flow. Larger disturbances, though rare, may favor the establishment of shade-intolerant species such as Pseudotsuga menziesii (Douglas-fir) (Agee, 1993).

Rubus spectabilis (salmonberry) and Gaultheria shallon (salal) may become very dense following a disturbance and can potentially form large brushfields (Tirmenstien,1989). Both species can reproduce vegetatively. Though these brush species are most prevalent in early to mid-seral successional stages, they persist in the openings of reference Sitka stands. Baccharis pilularis (coyotebrush) and Rubus discolor (Himalayan blackberry) may occur more frequently where fire has been previously utilized. Windborne spores from Polystichum munitum (western swordfern) may also rapidly infill new openings. It is found throughout successional communities and will increase over time to become dominant (Zinke, 1977).

Sitka spruce seed will germinate on almost any substrate, although mineral soil or a mixture of mineral soil and organic soil are considered the best seedbeds. The "nurse log syndrome" has a key role in the regeneration of Sitka spruce in its wetter environments, such as this LRU. Germination and seedling survival are greater on rotting logs then on the forest floor. Seedling establishment and growth can be enhanced with the inoculation of the mycorrhizal fungi, Thelephora terrestris. Sitka spruce shows strong trends in hardiness and growth in relation to geographic origination. These trends can be used to increase growth rate, but they can also have adverse effects on survival.

Fire is rare in Sitka spruce forests due to the constant high humidity in this zone and relatively high annual precipitation. Its thin bark and a shallow root system make it very susceptible to fire damage (Griffiths, 1992). Natural fire intervals very near the ocean where Sitka spruce grows are generally very long, ranging from 250 to 500 years. If fires occur in this ESG, they are typically very intense and usually result in total stand replacement at very infrequent intervals.

Sitka spruce may also rapidly invade adjacent coastal prairies that have been managed through burning or farming (Franklin and Dyrness, 1973). Red alder will also invade disturbed areas and form dense even-aged stands. The persistence of red alder on this site is thought to be related to the frequent soil movement and natural disturbance found along the coastal areas. Red alder fixes nitrogen which results in a higher availability of nitrogen in the soil (Uchytil, 1991).

References and Citations:

Agee, James. (1996). Fire Ecology of Pacific Northwest Forests. The Bark Beetles, Fuels, and Fire Bibliography.

Barbour, M., Keeler-Wolf, T., & Schoenherr, A. A. (Eds.). 2007. Terrestrial vegetation of California. Univ of California Press.

Burgess, S. S. O., & Dawson, T. E. 2004. The contribution of fog to the water relations of Sequoia sempervirens (D. Don): foliar uptake and prevention of dehydration. Plant, cell & environment, 27(8), 1023-1034.

Franklin. J.F. & C.T. Dyrness. 1973. Natural vegetation of Oregon and Washington. United States Department of Agriculture, Forest Service, General Technical Report PNW-8. p. 417.

Fryer, Janet L. 2008. Notholithocarpus densiflorus. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: www.fs.usda.gov/database/feis/plants/tree/notden/all.html / [2024, January 9].

Greenlee, J.M. and J.H. Langenheim. 1990. Historic Fire Regimes and Their Relation to Vegetation Patterns in the Monterey Bay Area of California. American Midland Naturalist, vol 124: 239-253.

Griffith, Randy Scott. 1992. Picea sitchensis. 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/picsit/all.html [2024, January 9].

Griffith, Randy Scott. 1992. Sequoia sempervirens. 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/seqsem/all.html [2024, January 9].

Jacobs, Diana F., D.W. Cole, and J.R. McBride. 1985. Fire History and Perpetuation of Natural Coast Redwood Ecosystems, Journal of Forestry, Volume 83, Issue 8: 494–497. https://doi.org/10.1093/jof/83.8.494

Johnstone, J. A., & Dawson, T. E. 2010. Climatic context and ecological implications of summer fog decline in the coast redwood region. Proceedings of the National Academy of Sciences, 107(10), 4533-4538.

Koopman, M, D. DellaSala, P. Mantgem, B. Blom, J. Teraoka, R. Shearer, D. LaFever, and J. Seney. 2014. Managing an Ancient Ecosystem for the Modern World: Coast Redwoods and Climate Change. RedwoodsManuscript20141016 (climatewise.org). Accesse 9 Jan. 2024.

Munster, J., & Harden, J. W. 2002. Physical data of soil profiles formed on Late Quaternary marine terraces near Santa Cruz, California (No. 2002-316). US Geological Survey.

Noss, R.F. 1999. The Redwood Forest History, Ecology, and Conservation of the Coast Redwoods. Save the Redwood League. 366 pages.

Painter, Elizabeth L. “Threats to the California Flora: Ungulate Grazers and Browsers.” Madroño, vol. 42, no. 2, 1995, pp. 180–88. JSTOR, http://www.jstor.org/stable/41425065. Accessed 9 Jan. 2024.

Tirmenstein, D. 1990. Vaccinium ovatum. 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/shrub/vacova/all.html [2024, January 9].

Uchytil, Ronald J. 1991. Pseudotsuga menziesii var. menziesii. 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/psemenm/all.html [2024, January 9].

Varner, J.M. and E.S. Jules. 2016. The Enigmatic Fire Regime of Coast Redwood Forests and Why it Matters. Proceedings of the Coast Redwood Science Symposium, Sequoia Conference Center, Eureka, CA. pp. 15-18.

Veirs, S. D. 1996. Ecology of the coast redwood. In J. LeBlanc (technical coordinator) Proceedings of the conference on coast redwood forest ecology and management (pp. 9-12).

Zinke, Paul J. 1977. Mineral cycling in fire-type ecosystems. In: Mooney, Harold A.; Conrad, C. Eugene, technical coordinators. Proc. of the symposium on the environmental consequences of fire and fuel management in Mediterranean ecosystems; 1977 August 1-5; Palo Alto, CA. Gen. Tech. Rep. WO-3. Washington, DC: U.S. Department of Agriculture, Forest Service: 85-94.

Major Land Resource Area

MLRA 004B
Coastal Redwood Belt

Stage

Provisional

Contributors

Kendra Moseley