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 covers the stable, rarely flooded, yet mostly fluventic soils along the valley bottom stream terraces of LRU I. It occurs on moist stream terraces adjacent to creeks and rivers on slopes that are nearly level to gently sloping, and low elevation slopes that are within 5-6 miles of the ocean and under 500 ft. in elevation.

Climate

This ESG is limited to areas of high annual precipitation, and a cool, maritime climate that provides fog drip and sufficient summer moisture to mollify evapotranspiration rates in the summers. 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. In some factors, this region has more similarities to the temperate rain forests of the Oregon and Washington Coast Ranges, however since it does not receive winter snow and colder temperatures and still maintains the distinct presence and dominance of coast redwood make this LRU unique to MLRA 4B.

Winter storms in this ESG can cause top breakage. This breakage may kill individual or groups of trees and create small openings from windfall (Noss, 2000). This would likely favor the establishment of redwood and other shade tolerant conifers. On alluvial sites with periodic flooding, redwood may dominate, along with other colonizing hardwoods (Veirs, 1996). Where existing redwoods are inundated, new roots develop in newly deposited silt (Veirs, 1996).

Soil features

Although coast redwood can grow on a variety of soils, the soils most associated with this floodplain-centered concept are primarily found on alluvium derived from sandstone, with very deep soils that range from very poorly drained to well-drained and are slightly acidic at 40 inches. They have a dominantly loamy subsurface rock content ranging from non-gravelly to gravelly.

Vegetation dynamics

This provisional ecological site concept attempts to describe the somewhat “iconic” coast redwood dominated stream terrace forests that can be found within this LRU. This concept is primarily supported through literature and available information from Redwood National and State Park Soil Survey. 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.

Sequoia sempervirens (coast redwood) forests are unique in this LRU in their ability to dominate the low elevations of LRU I that are solidly within the coastal fog influence.

Primary Disturbances

Fire and occasional flooding events are the most dominant disturbances to this ecological site concept, however, the historical origin of fires and flooding regimes within the Northern Redwood Region remains enigmatic (Varner and Jules, 2016). Lightning-ignited fires would likely spread due to the winds that are frequent within this LRU. However, Native American burning is thought to have played a major role by burning fires from the interior into the redwood zone (Veirs, 1996). Natural fire intervals were frequent as the northern range of redwoods evolved within a low to moderate natural disturbance regime (Veirs, 1996). Overall, the fire history studies conducted in redwood forests consistently show frequent fires that contrast sharply with the notion of a rainforest ecosystem (Varner and Jules, 2016).

Surface fires likely modified the tree species composition by favoring the thicker-barked redwood and killing western hemlock (Tsuga heterophylla), tanoak (Notholithocarpus densiflorus) and grand fir (Abies grandis) (Veirs, 1996). Western hemlock's shallow roots and thin bark make it susceptible to fire damage (Arno, 2002). The establishment of a western hemlock understory is increased by surface fires. This is due to the exposure of mineral-rich soil and the reduction of other plant competition (Veirs, 1996). Tanoak seedlings and sapling-sized stems are often top-killed by surface fire, though larger stems may survive with only basal wounding (Fryer, 2008).

A moderate fire could lead towards more of a mosaic in regeneration patterns. Patches of trees would be killed leaving others slightly damaged or unharmed. Douglas-fir (Pseudotsuga menziesii) regeneration would be favored in the large gaps that are created following a moderate fire, potentially leading to a larger proportion of Douglas-fir to redwood for several centuries (Agee, 1996). Without these gaps caused by fire, Douglas-fir regeneration is unsuccessful, and with continued lack of disturbance it may slowly be replaced by redwood as the dominant canopy species (Veirs, 1996).

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