Wilder Ridge
Location
39.820833, -122.625
Wilder Ridge Research Natural Area
This established RNA is located on the east edge of Corning Ranger District in Mendocino National Forest. It lies on the east slope of the North Coast Ranges in Tehama County and encompasses most of section 26 T23N, R7W MDBM (39°49'15"N., 122°37'30"W.), USGS Newville quad. Ecological subsection – Western Foothills (M261Ca).
Target element: chamise (Adenostoma fasciculatum) chaparral
Secondary target(s): foothill pine – blue oak woodland
Ecological and Physical Description
The total area in Wilder Ridge RNA is 570 acres (231 ha). From the valley bottom on the eastern edge to the crest of Wilder Ridge on the west of the RNA, the elevation range is about 854 ft (260 m). Several small ridges branch out from Wilder Ridge running toward the east. The slopes on the Wilder Ridge are extremely precipitous with some up to 80% (38°). The branching ridges are gentle, with 5-15% (3-8°) slopes on top and 20-30% (11-17°) on slopes between ridgetops and the drainages. In the RNA, several knobs exist. Elevations of the knobs range from 1200 ft (366 m) to just over 1500 ft (457 m).
Distinctive Features
Wilder Ridge, running north-south on the west border of the RNA, is the dominant physical feature. It is on an outlying range east of the main body of the Coast Range. The dominant botanical feature is chamise chaparral, which covers most of the RNA. Intermingled with small areas of foothill pine (Pinus sabiniana)-oak woodland and non-native grassland, the chamise chaparral is typical for areas north of the Carquinez Strait in the inner Coast Range.
Rare Plants: Two CNPS List 1B plants occur in the RNA, Eriastrum brandegeae and Antirrhinum subcordatum. Both are found in the chamise chaparral vegetation type.
Rare Fauna: The presence of Peregrine falcon (Falco peregrinus anatum, Federally- and State-listed endangered species) in the RNA has been confirmed, and that of prairie falcon (Falco mexicanus, State-listed species of special concern) has been suggested strongly by surveys conducted by Forest Service employees.
Association Types
Pure chamise covers the upper third of the slope and all but the north aspects of draws. The north-facing slopes contain a mixed shrub type of manzanita (Arctostaphylos spp.), toyon (Heteromeles arbutifolia), California bay (Umbellularia californica), scrub oak (Quercus dumosa), and some interior live oak (Quercus wislizenii). The middle third of the area is predominantly chamise with small groups of young foothill pine and scattered, older foothill pine jutting through the shrubs. There are some small openings of annual grass occurring in this zone, with several varieties of small herbaceous and woody plants on the north aspects. The east edge of the area is grassland or savannah type; ground cover is predominantly annual grasses with sparse blue oak (Quercus douglasii) overstory.
Chamise Chaparral (37200): This is the major vegetation type in the RNA, covering approximately 340 acres (138 ha). Adenostoma fasciculatum is the dominant species. It occupies higher elevations of the western third of the RNA, with nearly 100% cover and a height of 5.0 to 6.6 ft (1.5-2.0 m). In the center portion of the RNA, chamise chaparral is more open than that of the west third of the RNA and interspersed with foothill pine and manzanita. In the eastern third of the RNA, the chaparral is open with highly diversified annual and perennial herbaceous species. On steeply plunging slopes within this vegetation type, open woody populations of Eriodictyon californicum, Ceanothus cuneatus, Eriogonum nudum, and Eriophyllum confertifolium are often found. Understories are herbaceous species including Avena barbata, Linanthus ciliatus, and Sanicula bipinnata. Small areas of woodland associated with ephemeral riparian systems and subsurface flows also are included in this vegetation type. Interior live oak, cottonwood (Populus fremontii), willows (Salix spp.), toyon, California buckeye (Aesculus californica), mountain mahogany (Cercocarpus betuloides), western redbud (Cercis occidentalis), foothill pine, and poison oak (Toxicodendron diversilobum) are notable in these areas.
Foothill Pine-Oak Woodland (71410): Foothill pine and blue oak are the characteristic species of this vegetation type. Other species include Ceanothus cuneatus, Haplopappus linearifolius, Elymus caput-medusae, Gilia tenerrima, Bromus rubens, and Bromus mollis. Distribution of this woodland is fragmental, due to soil conditions. Soils here are shallow lithosols, classified as Millsholm clay loam, which support the chaparral community. However, in places where tree roots can penetrate (soils are deep or fracture planes occur in the parent material), the woodland community replaces the chaparral. The woodlands occur on a range of slopes and exposures but are most apparent on gently sloping, broad ridgelines, along drainage bottoms, and on north-facing slopes.
Non-Native Grassland (42200): This vegetation type occurs on the east margin of the RNA. It is the area where cattle grazing is concentrated and where human use may have occurred. Along with introduced annual grasses such as Aira caryophyllea, Avena barbata, Bromus rubens, Bromus mollis, and Festuca dertonensis, there are also native grasses and forbs such as Plantago hookeriana, Salvia columbariae, Melica californica, and Poa scabrella. Rarely, on the ephemeral stream bank, small patches of deergrass (Muhlenbergia rigens) can be found. On the shallow soil in the northeast corner of section 26, Eriogonum wrightii ssp. membranaceum (undetermined, Isle personal communication 1996) grows.
Plant Diversity
At least 95 vascular plant species occur in the RNA.
Conflicting impacts
There is one grazing allotment in the RNA. Most of the grazing takes place in the main valley along the east edge of the RNA, in the open savannah with moderate slopes. Cattle trails also are found in open chaparral, but the impacts of trampling and chiseling are limited to those routes only. The primary impact of grazing on the vegetation of Wilder Ridge RNA may have been the replacement of native grasses with introduced annuals. This is typical of much of California grasslands, and current grazing levels are not thought to alter this condition.
The climate is Mediterranean with wet, cool winters and warm, dry summers. More than 90% of the precipitation is concentrated between October and April. The nearest weather station is the Paskenta Ranger Station, from which complete precipitation data are available. Average annual precipitation is approximately 24 inches (61 cm). Other stations in the area with complete climatological data are Covelo and Orland, which represent the climatic extremes of Wilder Ridge RNA. Climate in the RNA is in the middle of a gradient from coastal on the west (Covelo, 55.3 °F [12.9 °C] average annual temperature) to inland (Sacramento Valley) on the east (Orland, 61.4 °F [16.3 °C] average annual temperature).
Soils in the RNA are generally shallow to very shallow and highly eroded.
Several unnamed ephemeral drainages can be found in the RNA, flowing to the east. These drainages meet Salt Creek and then flow southeast. No perennial surface flow of water is present, but a subsurface flow is present throughout the year.
The last fire to occur in the RNA was in 1952. It apparently started on private land north of the RNA. There are no records of other fire events within the RNA. This relatively rare fire occurrence may be a result of the unique geological stratum, topographical position, and vegetation mosaic of the RNA. Fires from human ignitions are unlikely to spread into the RNA except from the north side. The ridgetop along the west edge of the RNA is underlain by a stratum that presents an unstable surface of very low fertility. This provides a broad firebreak of rocks almost bare of vegetation. Along the east boundary, vegetation is extremely sparse and appears to act more as a fuel break than as a source of ignitions. Vegetation along the south boundary is continuous, a mosaic of chaparral, woodland, and savannah similar to the RNA. Fire could spread into the RNA from this side, but there are no roads or habitations for many miles. Such conditions also allow the RNA to have an experimental fire regime because: (1) there is low risk of fire escaping out of the RNA, (2) it is protected from humancaused fires originating outside the RNA, and (3) it has clear, logical lines for controlling burns from within.
Publications
- Sheauchi Cheng. 2004. Wilder Ridge
- Sheauchi Cheng. 2004. Forest Service Research Natural Areas in California