Natural Resources
Conservation Service
Ecological site F004BX123CA
Douglas-fir-tanoak/tanoak,
upper mountain slopes,
clay loam
Accessed: 09/04/2026
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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.
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Figure 1. Mapped extent
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
Associated sites
F004BX114CA Oregon white oak/perrenial and annual grasses, mountain slopes, sandstone and mudstone, clay loam
F004BX114CA, upper slope oak woodlands, is found in conjuction with this ecological site.
F005XB101CA Douglas-fir/tanoak, mountain slopes, sandstone and mudstone, clay loam
F005XB101CA is associated with this ecological site but it is found on drier, more exposed ridges and slopes.
F005XB102CA Douglas-fir-tanoak/tanoak, mountain slopes, sandstone and mudstone, very gravelly clay loam
F005XB102CA is associated with this ecological site but it is found on drier, more exposed ridges and slopes.
Similar sites
F004BX109CA Douglas-fir/redwood/tanoak/California huckleberry, mountain slopes, sandstone and schist, clay loam
F004BX109CA is similar to this ecological site, but redwood occupies a significant percentage of the overstory.
F005XB101CA Douglas-fir/tanoak, mountain slopes, sandstone and mudstone, clay loam
F005XB101CA may be confused with this ecological site because of similar Douglas-fir/tanoak predominance; however, F005XB101CA has a different soil temperature and moisture regime, mesic and xeric, respectively. Additionally, F005XB101CA is less productive and may have chinquapin in the subcanopy.
F005XB102CA Douglas-fir-tanoak/tanoak, mountain slopes, sandstone and mudstone, very gravelly clay loam
F005XB102CA may be confused with this ecological site because of similar Douglas-fir/tanoak predominance; however, F005XB102CA has a different soil temperature and moisture regime, mesic and xeric, respectively. Additionally, F005XB101CA is less productive and may have chinquapin in the subcanopy.
F004BX102CA Douglas-fir-redwood/tanoak, mountain slopes, sandstone, clay loam
F004BX102CA is similar to this ecological site; however, redwood occupies a significant percentage of the overstory and productivity is higher.
Table 1. Dominant plant species
Tree (1) Pseudotsuga menziesii
(2) Lithocarpus densiflorusShrub (1) Lithocarpus densiflorus
Herbaceous Not specified
Physiographic features
This ecological site is found on mountain slopes in Redwood Valley, the Lacks Creek drainage, and east of the Bald Hills Road in the lower Klamath drainage. It occurs on uniform and convex positions of steep middle and upper slopes. This ecological site is further inland or at higher elevation than the physiographic range of redwood.
Table 2. Representative physiographic features
Landforms (1) Mountain slope
Flooding frequency None Ponding frequency None Elevation 495 – 3185 ft Slope 30 – 50 % Aspect Aspect is not a significant factor Climatic features
The climate of this ecological site is dominated by mild, rainy winters and relatively warm, dry summers. The total annual precipitation for this ecological site ranges from 80 to 100 inches, the majority of which falls October to May. Summer temperatures range from 75 to 90 degrees F.
Table 3 Representative climatic features
Frost-free period (average) 290 days Freeze-free period (average) 290 days Precipitation total (average) 100 in BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
No influencing water features occupy this site.
Soil features
This ecological site overlies well-drained, very deep and moderately deep soils that have developed from colluvium and residuum weathered from sandstone and mudstone. The soil temperature and moisture regimes are isomesic ustic, respectively.
Soils that have been tentatively correlated to this ecological site include the following from the CA605 North Humboldt and Del Norte Soil Survey Area:
Map unit Soil
543 Wiregrass
543 Rockysaddle
543 Scaath
537 Wiregrass
537 ScaathTable 4. Representative soil features
Surface texture (1) Gravelly loam
(2) Very gravelly silt loam
(3) Extremely gravelly
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderately slow to very slow Soil depth 20 – 0 in Surface fragment cover <=3" 0 – 5 % Surface fragment cover >3" Not specified Available water capacity
(0-40in)3.7 – 7.3 in Subsurface fragment volume <=3"
(Depth not specified)35 – 85 % Subsurface fragment volume >3"
(Depth not specified)0 – 50 % Ecological dynamics
This ecological site is found on mountain slopes of Humboldt County, CA in Redwood Valley, Lacks Creek drainage, and east of the Bald Hills Road in the lower Klamath drainage. The reference plant community consists of Douglas-fir (Pseudotsuga menziesii) as the dominant overstory species and tanoak (Lithocarpus densiflorus) occupying the subcanopy. The amount of each species present is dependent on past disturbances. Pacific madrone (Arbutus menziesii) and an occasional redwood (Sequoia sempervirens) can also be found on the site. The dominant shrub species in the understory is tanoak with a lesser component of California huckleberry (Vaccinium ovatum). Western modesty (Whipplea modesta) is the most common herbaceous species found on the site.
Coastal fog does not have a significant influence on this inland ecological site, and redwood is scarce on the landscape. The range of redwood is largely influenced by coastal fog, which ameliorates the effects of solar radiation on conifer transpiration rates (Daniel 1942). Fog is a critical source of water in the drier summer months for redwood, which has high transpiration rates. Fog drip and direct fog uptake by foliage may contribute significant moisture to understory species and the forest floor (Dawson 1998).
The northern California Coast Range evolved within a low to moderate natural disturbance regime, with severe fire intervals ranging from 50 years at the eastern extent of redwood (Veirs 1979) and 10 to 30 years in Douglas-fir-tanoak forests of the Klamath Mountains (Wills 1994). Fires could have historically occurred by lightning ignition or deliberate setting by Native Americans to create desirable hunting habitat (Veirs 1996).
Fire effects and the patterns of stand development in the mixed evergreen forest-type are complex and highly variable (Eyre, 1990). Depending on intensity, fires in this region can create a mosaic of tree age classes or even-aged regeneration. Frequent light fires may kill thin-barked Douglas-fir seedlings (Mahony and Stuart 2000), but mature Douglas-fir are fairly fire resistant. Tanoak and madrone are sensitive to fire but are able to re-sprout and so are able to maintain their presence following fire (Mc Murray, 1989). Tanoak can sustain a shrub-like form until the canopy is opened, and then may rapidly attain tree status (McDonald and Tappenier, 1987). As California huckleberry is typically a fire-dependent species, sprouting can be widespread following natural fire or site preparation treatments (Tirmenstein 1990).
Douglas-fir sapling establishment and growth may be hindered by competition from re-sprouting hardwoods (Harrington et al 1991), limiting the proportion of Douglas-fir saplings able to become dominant members of the stand. Gradually, Douglas-fir will infill from adjacent areas, and eventually overtop tanoak. This process could take many years depending on the size of the burned area.
Management decisions can also influence stand dynamics as disturbance from timber harvesting is likely to mimic fire. Intensive harvest and the use of fire for slash treatment could favor hardwoods and limit Douglas-fir regeneration. Aerial seeding in past decades in the Redwood Creek basin have led to Douglas-fir dominated stands in some areas of the redwood region, skewing the natural overstory species composition (Noss 2000). However, large redwood stumps are absent throughout this ecological site, suggesting Douglas-fir is naturally the dominant conifer on this site.
Wind damage from winter storms can cause canopy top breakage which may kill individual trees or create windthrow gaps in the forest (Noss 2000), providing a break in the canopy for saplings and subcanopy trees to exploit.
The effects of climate change on species distribution and viability need to be considered in this age of rapidly changed climate regimes. The western United States is already experiencing an increase in tree mortality across all tree cohort age classes, likely due to regional warming and water deficits (van Mantgem et al 2009). These forest structure changes may cause species to migrate to higher elevations, as much as 500-1000m, as temperatures increase in lower elevations (Urban et al 1993). Climate models project many different climate regimes for the north coast of California. One model predicts a warmer, wetter climate regime in which redwood may be able to expand into canyon live-oak-madrone and chaparral systems (Lenihan et al 2003) and likely Douglas-fir dominated stands adjacent the current redwood zone. Climate change and its effects on vegetation patterns should be considered along with historical perspectives in ecological site development.State and transition model
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More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 4 submodel, plant communities
State 5 submodel, plant communities
State 1
Reference State - Plant Community 1.1Community 1.1
Reference State - Plant Community 1.1The reference plant community for this site is the presumed historic plant community prior to European settlement. This reference community is characterized by an overstory dominated by Douglas-fir (Pseudotsuga menziesii), with a moderate cover of tanoak (Lithocarpus densiflorus) in the sub-canopy.
T1.1a) Block harvest or fire would open up light and nutrients for pioneer species and shrubs to dominate the site.
T1.1b) Partial cutting of Douglas-fir could result in tanoak temporarily dominating the site.Forest overstory.The overstory is primarily Douglas-fir with lesser amounts of and madrone (Arbutus menziesii).<br /> <br /> Beneath the primary overstory tanoak often forms a sub-canopy with minor amounts of California bay (Umbellularia californica), canyon live oak (Quercus chrysolepis) and black oak (Quercus kelloggii). <br /> <br /> Average Percent Canopy Cover:<br /> <br /> Main canopy<br /> <br /> Douglas-fir 50-70%<br /> Madrone 5-10%<br /> <br /> Sub-canopy<br /> <br /> Tanoak 20-30%<br /> Other hardwoods <5%
Forest understory. The understory is dominated by shrubs, with tanoak and California huckleberry (Vaccinium ovatum) predominating.<br /> <br /> Average Percent Canopy Cover:<br /> <br /> Tanoak 10-20%<br /> California huckleberry 5-10%<br /> Pink honeysuckle 2-5%<br /> Common whipplea 2-5%<br /> Douglas-fir 2-5%<br /> Woodland strawberry 2-5%<br /> Salal 2-5%<br /> Madrone 2-5%<br /> Poison oak 2-5%<br /> Coyotebrush 1-5%<br /> Swordfern 1-5%<br /> Bracken fern 1-5%<br /> Common snowberry 1-5%<br /> California bay 1-2%<br /> Oregon grape 1-2%<br /> California blackberry 1-2%<br /> <br /> <br /> <br /> <br />
Table 5. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – 0-5% – 0-5% >0.5 <= 1 – 0-1% – 0-1% >1 <= 2 – – – 0-7% >2 <= 4.5 – 5-45% – – >4.5 <= 13 – 7-40% – – >13 <= 40 – – – – >40 <= 80 20-30% – – – >80 <= 120 50-75% – – – >120 – – – – State 2
Plant Community 1.2Community 2.1
Plant Community 1.2This plant community is dominated by the hardwoods tanoak and madrone, woody shrubs, and a variety of pioneering species.
T1.2a) If the site is left to develop, tanoak and madrone will form a tree layer and Douglas-fir will begin to infill from surrounding seed sources. Tanoak and madrone are fast growing and will dominate the site and compete with regenerating Douglas-fir for decades.
T1.2b) Mechanical or chemical hardwood management techniques could accelerate the establishment of Douglas-fir by decreasing competition from sprouting tanoak and madrone. Direct seeding or planting of conifers could also improve establishment.
State 3
Plant Community 1.3Community 3.1
Plant Community 1.3After initial establishment of hardwoods, Douglas-fir may regenerate under the hardwood canopy. In several decades, Douglas-fir may exceed the height of the hardwoods and become firmly established in the overstory.
T1.3a) A block harvest or severe fire would initiate the shrub community phase of this site.
T1.3b) Douglas-fir dominance could be regained by natural processes over several decades or could be accelerated by tree planting and hardwood management.
State 4
Plant Community 1.4Community 4.1
Plant Community 1.4Following hardwood management or several decades of ecological succession, Douglas-fir will dominate the overstory of this plant community phase and tanoak will occupy the subcanopy and understory.
T1.4a) Selective harvesting of Douglas-fir or a moderate fire could return this site to tanoak and hardwood dominance.
T1.4b) Time and an intermediate disturbance regime could create the opportunity for the site to transition towards the reference plant community.
State 5
Plant Community 1.5Community 5.1
Plant Community 1.5Selective harvesting of Douglas-fir could result in tanoak dominating the overstory with few Douglas-fir scattered throughout the site.
T1.5a) Douglas-fir dominance could be regained by natural processes over several decades or could be accelerated by tree planting and hardwood management.Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 7. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 8. Community 3.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 9. Community 4.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 10. Community 5.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
A wide variety of bird and animal species use the Douglas-fir/tanoak forest. The diversity of wildlife utilizing the site is influenced by the presence of the mast-producing tanoak as well as berry producing species such as California huckleberry, Pacific madrone and Oregon-grape (Mahonia nervosa).
Bird species that may utilize these upland sites include woodpecker, warbler, nuthatch, finche, and Stellar's jay. Other bird species include numerous hawks. Tanoaks are also used by cavity nesting birds, such as the downy woodpecker, northern flicker, red and white breasted nuthatch, brown creeper and house wren. Tanoak habitats are also food and nesting sites for the northern flying squirrel, Allen's chipmunk, and dusky-footed woodrat.
Mammals such as the black-tailed deer, black bear, Townsend chipmunk, California ground squirrel, and redwood chickaree utilize tanoak for food and cover.
Hydrological functions
The runoff class for these soils is high.
The hydrological group for the soils of this ecological site are as follows:
Wiregrass-543--C
Wiregrass-537--C
Scaath-543--C
Scaath-537--C
Rockysaddle-543--C
Refer to the Soil Survey Manuscript for further information.Recreational uses
This site can support a variety of recreational uses including hiking, camping, OHVs, mountain biking, and bird watching. This ecological site is found on public land open for recreation including NPS Redwood National Park and BLM Lacks Creek Management Area.
Slopes exceeding 25% may limit trail development.Wood products
Douglas-fir is employed in residential structures and light commercial timber-frame construction. It is also used for solid-timber heavy-duty construction such as pilings, wharfs, bridge components and warehouse construction.
The manufacturing of tanoak wood products is limited. Upper-grades produce good quality veneers and plywood. Tanoak flooring, paneling and decking have also been produced. Lower-grades are used to make pallets, crossties, mine timbers, baseball bats and tool handles. The wood had also been chipped for pulp and for use in the cogeneration of electricity. It is also widely utilized as firewood.
Other products
Tannin from tanoak bark is used commercially to cure leather.
Berries from California huckleberry are edible and are made into jams and pies. The foliage of Oregon grape and salal are utilized for decorative floral arrangements.
Wild mushrooms are often sought on this ecological site, especially chanterelles and morels, the later of which often emerge following fire.
Historically, tanoak acorns provided a dietary staple for native americans throughout the California Coast Ranges.Other information
Site productivity interpretations are based on the following site index curves:
Species Curve Base age
Douglas-fir 790 100 yearsTable 11. Representative site productivity
Common name Symbol Site index low Site index high CMAI low CMAI high Age of CMAI Site index curve code Site index curve basis Citation Douglas-fir PSME 110 150 98 158 – – – Supporting information
Inventory data references
Forestry data was collected in association with the following soils pits in the CA605 soil survey area: Soil and map unit pit # Wiregrass 543 81-005 03-0325 03-05007 03-05339 Rockysaddle 543 83-021 88-010 06-056A Scaath 543 04-016 Forestry plot# 05F111 05F114 09F064 09F045 09F057 05F112 05F113 09F082 09F089 09F090 09F044 09F081
Type locality
Location 1: Humboldt County, CA Township/Range/Section T8N R3E S28 UTM zone N UTM northing 4527977 UTM easting 429707 General legal description Hupa Mountain Quadrangle Other references
Agee J.K. 1993. Fire ecology of Pacific Northwest forests. Island Press. Covelo, CA.
Arno, S.F., Allison-Bunnell, S., 2002. Flames in our forest: disaster or renewal? Island Press, Washington, DC, 227 pp.
Daniel, T. W. 1942.The comparative transpiration rates of several western conifers under controlled conditions. Ph. D. Thesis. U. of Calif., Berkeley. 190 p.
Dawson, T.E. 1998. Fog in the California redwood forest: ecosystem inputs and use by
plants. Oecologia 117: 476-485.
Eyre, F.H., Editor. 1980. Forest Cover Types of the United States and Canada. Society of American Foresters.
Harrington, T.B., J.C. Tappeiner II and T.F. Hughes. 1991. Predicting average growth and size distributions of Douglas-fir saplings competing with sprout clumps of tanoak
or Pacific madrone. New Forests 5 : 109-130.
Lenihan, J.M., R. Drapek, D. Bachelet, R.P. Neilson. 2003. Climate change effects on vegetation distribution, carbon, and fire in California. Ecological Applications 13(6), 2003, pp. 1667–1681
Mahony T.M. and J.D. Stuart. 2000. Old-growth forest associations in the northern range of coast redwood. Madroño, Vol. 47 No. 1. pp 53-60.
McDonald, P.M. and J.C. Tappeniner II. 1987. Siliviculture, ecology, and management of tanoak in northern California. USDA Forest Service general technical report No. 100), p. 64-70.
Noss, R.F., editor. 2000. The redwood forest: history, ecology, and conservation of the coast redwoods. Save-the-Redwoods League. Island Press. Covelo, CA. 377 pages.
Tirmenstien, D. 1990. Vaccinium ovatum. In: Fire Effects Information System, U.S. Department of Agriculture, Forest Service, Fire Sciences Laboratory. Available: http://www.fs.fed.us/database/feis
Urban, D. L. M.E. Harmon C.B. Halpern. 1993. Potential response of Pacific Northwestern forests to climatic change, effects of stand age and initial composition Climate Change 23: 247-266.
van Mantgem, P.J., Stephenson, N.L., Byrne, J.C., Daniels, L.D., Franklin, J.F., Fulé, P.Z., Harmon, M.E., Larson, A.J., Smith, J.M., Taylor, A.H., and Veblen T.T., 2009. Widespread Increase of Tree Mortality Rates in the Western United States. Science 323:521-524.
Veirs, S.D. 1996. Ecology of the coast redwood. Conference on coast redwood ecology and management. Pg 9-12.
Veirs, S.D. 1979. The role of fire in northern coast redwood forest dynamics. Conference on Scientific Research in the National Parks.
Wills, R. D., and Stuart, J.D. 1994. Fire history and stand development of a Douglas-fir/hardwood forest in northern California. Northwest Science 68:205-212.
Contributors
Emily Sinkhorn
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
Author(s)/participant(s) Contact for lead author Date Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Sub-dominant:
Other:
Additional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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Average percent litter cover (%) and depth ( in):
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Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
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Perennial plant reproductive capability:
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