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 provisional ESG covers the mountains within proximity to the coast. It occurs on uniform to slightly convex summits and shoulders of broad ridges; and slightly concave to convex positions of mountain slopes in LRU I. These mountain slopes are sloping to very steep. Slopes are gently sloping to very steep reaching elevations just over 3000 ft, and the site 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 to allow redwoods to maintain co-dominance in the ecological site.

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.

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.

Soil features

Although coast redwood and Douglas-fir can grow on a variety of soils, the soils most associated with this concept are primarily found on colluvium and residuum materials derived from sandstone, conglomerate and mudstone, with soils that range from very deep to lithic that are primarily well-drained, and are moderately to strongly acidic at 40 inches. They have a dominantly loamy subsurface rock content ranging from non-gravelly to extremely gravelly.

Vegetation dynamics

This provisional ecological site concept attempts to describe the coast redwood-Douglas-fir dominated mountain slopes that can be found within this LRU. This concept is primarily supported through literature and available information from the 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) and Pseudotsuga menzeisii (Douglas-fir) forests are unique in this MLRA in their ability to dominate the low hills and mountains of LRU I that are solidly within the coastal fog belt, especially during the summer months.

Coast redwood attains a height of 395 ft (~120 m), and an age of at least 2200 years. Roots are shallow without a taproot. Trees begin bearing cones by 5 to 15 years of age and seed production is generally high, however seed viability is low. Wind and gravity disperse the seeds, with most falling within 395-400 ft of the parent tree. Seedling establishment is best on moist soil lacking litter but can occur on duff or logs. Plants are moderately shade tolerant, but they grow faster in higher light levels if soil moisture is present (Sawyer et. al., 2009).

Douglas-fir is a large, coniferous, evergreen tree. Adapted to a moist, mild climate, it grows bigger and more rapidly than the inland variety. Trees 5 to 6 feet (150-180 cm) in diameter (150-180 cm) and 250 feet (76 m) or more in height are common in old-growth stands. These trees commonly live more than 500 years and occasionally more than 1,000 years. Old individuals typically have a narrow, cylindric crown beginning 65 to 130 feet (20-40 m) above a branch-free bole. It often takes 77 years for the bole to be clear to a height of 17 feet (5 m) and 107 years to be clear to a height of 33 feet (10 m). In wet coastal forests, nearly every surface of old-growth Douglas-fir in this ecological site is often covered by epiphytic mosses and lichens (Griffiths, 1992). This tree's rooting habit is not particularly deep. The roots of young Douglas-fir tend to be shallower than roots of many of the same aged conifers like ponderosa pine, sugar pine, or incense-cedar. Some roots are commonly found in organic soil layers or near the mineral soil surface.

This ecological site is dominated by a multi-tiered canopy of conifers, with coast redwood making up more than 50% of the stands basal area and Douglas-fir and other hardwoods accounting for between 30-50%. Pacific rhododendron and tanoak readily establish after disturbance and may dominate the overstory for several years post-disturbance. Fallen logs are an essential part of this ecological site, providing significant habitat for wildlife species and conifer recruits. Conifer recruitment on the bare mineral soil is rare, due to the thick litter layer and organic surface soil and is therefore relegated only to areas of surface soil disturbance from mass wasting, logging practices, wind throw, and recreation trails.

Primary Disturbances

Fire is the principal disturbance agent in both young-growth and old-growth stands, however, fire regimes within the Northern Redwood Region remain enigmatic (Varner and Jules, 2016). Fire scars are abundant throughout old-growth stands (Norman et al. 2009). 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 (Norman et al. 2009, Varner and Jules, 2016). The mean fire interval is quite variable, depending on environmental site conditions. Old-growth stands show evidence of three or more severe fires each century, and the distribution of fires appears as a natural pattern of several short intervals between fires followed by one or more long interval (Stuart 1987, Jacobs et al. 1985).

Previous harvesting and the use of fire to treat logging slash in this area has also changed species composition on many formerly redwood-dominated sites (Noss, 1999). Within many areas of Redwood National Park, which includes large areas of this ecological site group concept, aerial seeding of Douglas-fir has led to a 10:1 ratio of Douglas-fir to redwood (Noss, 1999). The co-dominance of Douglas-fir in this provisional ecological site concept indicates a more regular occurrence of fires and disturbance, since Douglas-fir requires exposed soil to successfully regenerate.

Redwood and tanoak can re-sprout following fire. After fire, redwood may sprout from the root crown or from dormant buds located under the bark of the bole and branches (Veirs, 1996, Noss, 1999), while tanoak will sprout from the root crown, root collar, lower part of the stem and underground burls (McDonald and Tappeiner 1987). The sprouting ability of redwood is most vigorous in younger stands and decreases with age, while the ability to survive fire increases with age as its fibrous bark thickens. Frequent fire reduces tanoak’s sprouting ability and tends to keep understories open (Arno, 2002). Fire exclusion would allow for the gradual increase of tanoak in the understory (McMurray, 1989). Surface fires likely modified the tree species composition by favoring the thicker-barked redwood and killing young tanoak. Fires also expose the mineral-rich soil and reduce competition from other plants, thereby increasing the establishment of Douglas-fir (Veirs, 1980, Agee, 1993). 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 a mosaic in regeneration patterns. Patches of trees would be killed leaving others slightly damaged or unharmed. Douglas-fir 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).

Fires will also alter the composition of shrubs and forbs in the understory community. Vaccinium ovatum (evergreen huckleberry) is a common species in both moist and dry Douglas-fir and redwood environments. It is normally a fire-dependent shrub species, but little is known concerning its adaptation to fire under low to moderate fire return intervals (Tirmenstein, 1990). Following a fire, evergreen huckleberry will often re-sprout and recover rapidly. Rhododendron macrophyllum (Pacific rhododendron) is considered sensitive to fire. Following a surface fire, it may reestablish seedlings by sprouting from the root crown or stem base (Duchac, 2021). After a disturbance such as fire, a decrease in plant cover is common, and will be followed by a gradual increase in cover over time.

Another important disturbance in the redwood zone is winter storms that can cause top breakage and blowdown. This breakage may kill individual or groups of trees and create small openings from windfall (Noss, 1999). This would likely favor the establishment of redwood and other shade-tolerant conifers.

Coast redwood is one of the signature trees of California, with 95% of its range existing within the state. Years of logging have left significantly lower amounts of the original forest (Sawyer et al. 2009). Old-growth stands exist mainly in protected areas including parks, experimental forests, and private reserves. Asexual regeneration is prolific and many stands of younger trees exist, but many areas are on the third cycle of regeneration with collateral impacts of erosion, streambed siltation, and alteration to watershed and wildlife values. Residential development is an increasing concern.

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.

Duchac, Leila. 2021. Rhododendron macrophyllum, Pacific rhododendron. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). Available: www.fs.fed.us/database/feis/plants/shrub/rhomac/all.htm.

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.

McDonald, P. M., & Tappeiner II, J. C. (1987). Silviculture, ecology and management of tanoak in northern California. In Proceedings of the Symposium on Multiple-use Management of California's Hardwood Resources, November 12-14, 1986, San Luis Obispo, California. General Technical Report PSW-100 (pp. 64-70). Berkeley, CA: Pacific Southwest Forest and Range Experiment Station, Forest Service, US Department of Agriculture.

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.

Norman, S.P., Varner, J.M., Arguello, L., Underwood, S., Graham, B., Jennings, G., Valachovic, Y. and Lee, C., 2009. Fire and fuels management in coast redwood forests.

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

Olson, D. F., Roy, D. F., & Walters, G. A. 1990. Sequoia sempervirens (D. Don) Endl. Redwood. Silvics of North America, 1, 541-551.

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.

Sawyer, J.O., T. Keeler-Wolf, and J.M. Evens. 2009. A Manual of California Vegetation, Second Edition. California Native Plant Society, Sacramento, CA. 1300 pp.

Stone, E.C., R.B. Vasey. 1968. Preservation of coast redwood on alluvial flats. Science 159:157-161.

Stuart, J.D. 1987. Fire history of an old-growth forest of Sequoia sempervirens (Taxodiaceae) forest in Humboldt Redwoods State Park, California. Madroño 34(2):128-141.

Stuart, J.D., S.L. Stephens. 2006. North Coast Bioregion. In .N.G. Sugihara et al. Fire in California’s Ecosystems. University of California Press, Berkeley. pp. 147-169.

Tappeiner II, J. C., & McDonald, P. M. (1984). Development of tanoak understories in conifer stands. Canadian Journal of Forest Research, 14(2), 271-277.

Tesky, Julie L. 1992. Tsuga heterophylla. 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/tsuhet/all.html [2024, January 9].

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 Jr, S. D. (1980). The role of fire in northern coast redwood forest dynamics. In Proc. Second Conf. Scientific Research in National Parks (Nov. 26-30, 1979) San Francisco, Ca_ (Vol. 10, pp. 190-209).

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.
Williamson, R. L. 1976. Natural regeneration of western hemlock. In Proceedings, Western Hemlock Management Conference, May: pp. 166-168.

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

Subclasses

• F004BX101CA–Redwood/Douglas-fir/Pacific rhododendron, mountain slopes, schist, clay loam
• F004BX102CA–Douglas-fir-redwood/tanoak, mountain slopes, sandstone, clay loam
• F004BX103CA–Redwood-Douglas-fir/Pacific rhododendron, mountain slopes, sandstone, clay loam
• F004BX104CA–Redwood-Douglas-fir/Pacific rhododendron, ridge-tops, schist, red clay
• F004BX105CA–Douglas-fir/tanoak/California huckleberry, ridge-tops, schist, red clay
• F004BX106CA–Redwood/Douglas-fir/California huckleberry/western swordfern, hills, soft sandstone, very gravelly loam
• F004BX107CA–Redwood/western swordfern, hills, soft sandstone, clay loam
• F004BX109CA–Douglas-fir/redwood/tanoak/California huckleberry, mountain slopes, sandstone and schist, clay loam

Stage

Provisional

Contributors

Kendra Moseley