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Chapter 2 -- Description of the Smith River watershed (continued)

Soils and Vegetation

One of the main factors that influences vegetation communities is soil type. To help understand patterns in vegetation communities, the watershed is divided into subsections that have certain characteristic soil types. Vegetation communities also vary due to variations in precipitation and evapotranspiration, especially the increase in evapotranspiration that occurs with increasing distance from the coast.

Soils on the coastal plain are formed from marine terrace deposits and are dominated by agriculture. Types of vegetation on the coastal plain include agricultural crops, pasture, grand fir-Sitka spruce forest, redwood forest, coastal grass-shrub, and coastal prairie-scrub mosaic. In the Smith River estuary, coastal salt marshes are found (Table 13, California 1977).

 

Table 13. Potential natural vegetation types, Crescent City Plain subsection of the Smith River watershed (California 1977).

Potential natural vegetation type

Typical genera

Coastal salt marsh

Salicornia - Spartina

Coastal grass - shrub community

Elymus - Baccharis

Coastal prairie - scrub mosaic

Baccharis - Danthonia - Festuca

Grand fir - Sitka spruce forest

Abies - Picea

Redwood forest

Sequoia - Pseudotsuga

 

Sedimentary deposits of the Northern Franciscan subsection have developed into deep fertile soils (California Department of Fish and Game 1980). In these areas, marine influence is strong and fog is common in the summer. Because of favorable soils and low evapotranspiration stress, this subsection supports outstanding redwood and Douglas fir forests. Redwoods dominate low elevation forests. Tanoak and madrone are also common. Many forests have been logged and are now in early seral stages. Blocks of old growth forest remain, the largest being within Jedidiah Smith State Park.

The Gasquet Mountain Ultramafic subsection is characterized by serpentine soils developed from Mesozoic ultramafic intrusive rocks. Due to harsh soils, this subsection has more open forests such as the Jeffrey pine forest type. Typically in these areas, Jeffrey pine is the only conifer although incense cedar, western white pine, sugar pine, knobcone pine, huckleberry oak, and manzanita are sometimes present (Franklin and Dyrness 1988). The mixed evergreen forest type is also found in the Gasquet Mountain Ultramafic subsection. Dominant species of the mixed evergreen forest are madrone, chinquapin, tanoak, and Douglas fir. Because this subsection is farther inland, marine influence is reduced and more drought tolerant vegetation is found.

The greatest concentration of endemic plants in North America occurs on the ultramafic soils of the Smith River watershed and neighboring areas. Especially in the North Fork subbasin, serpentine soils support unique plant communities and 27 rare plants (Cooperrider and Garrett 1995, Table 14).

 

Table 14. Sensitive plant species that occur on mining claims within the North Fork subbasin of the Smith River, Del Norte County, California (McCain et al. 1995).

Name of claim:

Species:

Cal-Nickel #33

Howell’s jewel flower

 

MacDonald’s rock cress

 

Oregon bleeding heart

 

Siskiyou indian paintbrush

 

Waldo buckwheat

 

Waldo gentian

 

Western bog violet

   

Bluewater #10

Koehler’s stipitate rock cress

 

MacDonald’s rock cress

 

Siskiyou indian paintbrush

   

Bluewater #8

Opposite-leaved lewisia

 

The parent materials for the Western Jurassic subsection are predominantly Mesozoic sediments, Jurassic-Triassic metavolcanics, Mesozoic basic intrusives, Upper Jurassic marine sediments, and Mesozoic ultra-basic intrusives. Although this subsection has a variety of soil types, the most common vegetation type is mixed evergreen forest dominated by Douglas fir, madrone, tanoak, canyon live oak, and chinquapin. Areas of Jeffrey pine, incense cedar, western white pine, huckleberry oak, manzanita, and ceanothus are also found.

The soils and vegetation of the Siskiyou Mountains are diverse. Parent materials include Mesozoic sediments, Mesozoic metavolcanics, and Mesozoic ultramafic intrusives. Soils developed from sedimentary parent materials tend to be steep and support Douglas fir forests. Granitic geology occurs mostly at high elevations where evapotranspiration stress on vegetation is less. Soils developed from granitic parent materials generally support mixed conifer forests including true firs, Douglas fir, and mountain hemlock. Soils developed from the metamorphosed volcanic parent materials are usually low to medium in timber productivity and may be brushy. This area also has ultramafic soils that support unusual vegetation communities.

In the drier fire-prone inland areas, there are scattered stands of knobcone pine (Pinus attenuata) and lodgepole pine (P. contorta) (Table 15). These "closed cone" pines depend on fire to produce conditions favorable for reproduction. Their cones generally remain sealed until the heat of a forest fire causes them to open and release their seeds (Tuffly 1995). In inland areas, forests at low elevations consist of a mixture of conifers and hardwoods, typically including Douglas fir, tanoak, canyon live oak, and madrone.

 

Table 15. Vegetation types in the Smith River National Recreation Area, Del Norte County, California (McCain et al. 1995).

Vegetation series

% of total

Acreage

Conifer forest

   

Tanoak

48.4

160,879

Douglas fir

23.3

77,416

Lodgepole pine

14.2

47,199

White fir

4.8

15,816

Red fir

2.5

8,388

Port Orford cedar

1.5

5,106

Jeffrey pine

1.5

4,878

Western white pine

0.6

2,047

Redwood

0.3

892

Knobcone pine

0.2

728

Hardwood forest

   

Alder

1.1

3,680

Canyon live oak

0.6

2,066

Oak woodlands

   

White oak

0.1

261

Black oak

<0.1

58

Grassland

0.1

276

Non-vegetation

0.8

2,529

Total: 519 sq mi

 

332,217

 

The Siskiyou Mountains have the highest diversity of conifers in North America (Table 16). The diversity of conifers and other vegetation is partly due to the diversity of soils and highly variable topography and microclimate. In addition, climatic and geologic history has contributed to the diverse vegetation of the area. Because the Smith River watershed has been continuously vegetated for 65 million years, it has developed a greater diversity of plants than areas subjected to extreme climatic conditions or submergence (Cooperrider and Garrett 1995).

 

Table 16. Tree species of the Smith River watershed (Griffin and Critchfield 1972).

Scientific name

Common name

Distribution

Abies concolor

White fir

High Siskiyous

Abies grandis

Grand fir

Coastal

Abies magnifica

Red fir

High Siskiyous

Acer macrophyllum

Big leaf maple

Widespread

Alnus rhombifolia

White alder

Riparian inland

Alnus rubra

Red alder

Riparian widespread

Arbutus menziesii

Madrone

Widespread

Castanopsis chrysophylla

Chinquapin

Scattered inland

Chamaecyparis nootkatensis

Alaska yellow cedar

Siskiyou Crest

Chamaecyparis lawsoniana

Port Orford cedar

Scattered moist areas

Cornus nuttallii

Pacific dogwood

Scattered inland

Fraxinus latifolia

Oregon ash

Riparian uncommon

Librocedrus decurrens

Incense cedar

Scattered inland

Lithocarpus densiflorus

Tanoak

Widespread low elevations

Picea brewerana

Brewer spruce

High Siskiyous scattered

Picea sitchesis

Sitka spruce

Coastal

Pinus attenuata

Knobcone pine

Scattered high and mid elev

Pinus contorta

Lodgepole/shore pine

Scattered high and mid elev

Pinus jeffreyi

Jeffrey pine

Scattered inland

Pinus lambertiana

Sugar pine

Scattered inland

Pinus monticola

Western white pine

Scattered high elevations

Pinus ponderosa

Ponderosa pine

A few stands high elevations

Populus trichocarpa

Black cottonwood

Scattered riparian

Pseudotsuga menziesii

Douglas fir

Throughout the basin

Quercus chrysolepis

Canyon live oak

Scattered

Quercus garryana

Oregon white oak

A few areas

Quercus kelloggii

California black oak

A few areas

Salix sp.

Willow

Riparian areas

Sequoia sempervirens

Coast redwood

Coastal

Taxus brevifolia

Pacific yew

Eastern areas

Thuja plicata

Western red cedar

Scattered mostly coastal

Tsuga heterophylla

Western hemlock

Mostly coastal

Tsuga mertensiana

Mountain hemlock

High Siskiyous

Umbellularia californica

California bay laurel

Low elevations

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