Soils and Geology
The topography of HREC is characterized by a series of rounded ridges and benches rising steadily to the northeast (see topographical map). An intricate network of seasonal, high gradient tributaries dissect this landscape forming steep ravines and V-shaped channels before emptying into Parson's Creek. Numerous vernal pools occupy benches and soil slip depressions where the underlying hardpan layer consists of fine-grained clay soils. Near the southern end of HREC, a series of small permanent sag ponds have formed in a trough along the NW-SE trending Mayacama fault line, comprising Lake Biological Area.
Gowans (1958) conducted a soil-vegetation survey of HREC. There is also a 1991 USDA Natural Resources Conservation Service (NRCS) Soil Survey of Mendocino County (in HREC Library) which is more accurate than the Gowans survey regarding nomenclature, but less precise because it is on a much larger scale. The NRCS soil survey provides land use and erosion control information specific to the soil types as well.
Geologically, HREC land is part of the Franciscan Formation (Jurassic), consisting of sedimentary rocks and interbedded volcanics. Greywacke sandstone with basalt and serpentine comprises the interbedding, all with deeply broken fault gouge zones. The dominant rocks are composed of six medium-textured soils of the Laughlin, Josephine, Sutherlin, Maymen, Los Gatos, and Hugo series. The Yorkville soils are a heavy clay characterized by landslips and seep areas. Less represented soil series at HREC are the Stonyford and Sobrante series, which formed on localized areas of basalt; Climax, derived from small areas of basalt and sandstone; and the Henneke and Montara series, derived from serpentine rock.
The moderately shallow soils of the Laughlin series are slightly acidic with depths ranging from 1 ft to 3 ft. Distributed throughout the lower elevations of HREC, these soils are on nonsteep to steep, partly rounded slopes. The Laughlin series is characterized by a vegetation cover of grasses with blue oak (Quercus douglasii), with a few areas of dense interior live oak (Quercus wislizenii) coverage.
The Josephine soils are distributed throughout the station and occur on nonsteep to steep slopes, most of which face toward the north or east. Surface soils are slightly acidic, subsurface soils are moderately acidic. Soil depths range from less than 36 inches to more than 60 inches. Typical vegetation of this soil is moderate to dense hardwoods with some shrubs and conifers. Dominant plants are black oak (Quercus kelloggii), madrone (Arbutus menziesii), and Douglas fir (Pseudotsuga menziesii).
Sutherlin soils, widely distributed on HREC, have developed from hard sandstone and shale and are typically grass-covered with scattered blue oaks and interior live oaks. Soil depth is usually less than 3 ft and surface soils are slightly acid. These soils are on nonsteep to steep rounded slopes.
Distinguished by landslips and seep areas, Yorkville soils occur across HREC on steep to nonsteep slopes. These are heavy clays with grass cover and blue oaks and valley oaks (Q. lobata) on stable areas.
Hugo soils are shallow soils (less than 36 inches in depth) that are slightly acidic and generally gravelly. These soils occur on rather steep north or east exposures. The few areas of Hugo soil at HREC occur in the northeastern portion of the Center, in upper James I and James III pastures. Native vegetation typical of this soil type is a dense cover of hardwood with some shrubs and conifers. Dominant plants are black oak, madrone, California buckeye (Aesculus californica), and Douglas fir.
Los Gatos series soils are rocky, generally steeply sloping, moderately acidic throughout, and shrub-covered. Most of these soils are found at the higher elevations of HREC and have depths of 12-24 inches. The dominant shrubs on this soil type are chamise (Adenostoma fasciculatum), wedgeleaf ceanothus (Ceanothus cuneatus), common manzanita (Arctostaphylos manzanita), eastwood manzanita (Arctostaphylos glandulosa), wavyleaf ceanothus (Ceanothus foliosus), and shrub interior live oak (Quercus wislizenii var. frutescens).
The soils of the Maymen series are typically shallow, steep, stony, and shrub-covered. Moderately acidic throughout, these soils are associated with rock outcrops and occur primarily at the higher elevations of HREC, in James I, James II, James III, and Orchard pastures and Riley Ridge Biological Area. Native vegetation on these soils consists of moderate to dense shrub cover of chamise and wedgeleaf ceanothus.
Serpentine soils are present at HREC and should be addressed because of the unique associated vegetation. Kruckeberg (1984) describes serpentine as a type of ultramafic rock in which iron and magnesium are chief elements. In California, these largely occur in the foothills of the Sierra Nevada and the Coast Ranges from San Luis Obispo County north to the Oregon border. Serpentine rock weathers to soils rich in magnesium, iron, silicates, and often exceptional amounts of nickel. The typical clay mineral is smectite (montmorillonite), which has a large shrink-swell capability. Serpentine soils have high values of exchangeable magnesium and exceptionally low values of exchangeable calcium. They are usually deficient in nitrogen and phosphorus, and can attain high values of heavy metals (esp. iron and nickel) in both soils and plant tissues. Kruckeberg (1984) mentions several factors contributing to the unique vegetation of serpentine soils: the imbalance of calcium and magnesium, magnesium toxicity, heavy metal toxicity, or low levels of essential nutrients. Drought stress, in addition to chemical imbalance, causes severe environmental conditions, thus the striking discontinuity between vegetation on serpentine soil and adjacent non-serpentine soil. In California, the vegetation change is often from oak woodland to chaparral, or chaparral to sparse grassland.
At HREC, the Montara and Henneke soil series are derived from serpentine rock. These soils occur in rather small units at higher elevations in the north central portion of HREC in Orchard pasture (Henneke) and a few small areas in the lower elevations (Montara) in the Foster, Watershed II, Vasser, West Vasser, and South pastures. The Montara series and more open Henneke areas have a grass cover of primarily the invasive barbed goat grass (Aegilops triuncialis). The rest of the Henneke area has a moderately dense to nearly open shrub cover including hoary manzanita (Arctostaphylos canescens), leather oak (Quercus durata, serpentine endemic), chamise, and Sargent cypress (Cupressus sargentii, serpentine endemic).
The most notable geologic formation on HREC is the Mayacama fault line which runs the length of the Center, southeast to northwest. Implications of this fault activity are that parts of the eastern portion of HREC are prone to landslides. The Alquist-Priolo Special Studies Zones maps in HREC library show locations of current and potential landslides. Seismic activity of the Mayacama fault line is monitored by the automated University of California-Berkeley seismic station located in Watershed I pasture.
Gowans (1958) conducted a soil-vegetation survey of HREC. There is also a 1991 USDA Natural Resources Conservation Service (NRCS) Soil Survey of Mendocino County (in HREC Library) which is more accurate than the Gowans survey regarding nomenclature, but less precise because it is on a much larger scale. The NRCS soil survey provides land use and erosion control information specific to the soil types as well.
Geologically, HREC land is part of the Franciscan Formation (Jurassic), consisting of sedimentary rocks and interbedded volcanics. Greywacke sandstone with basalt and serpentine comprises the interbedding, all with deeply broken fault gouge zones. The dominant rocks are composed of six medium-textured soils of the Laughlin, Josephine, Sutherlin, Maymen, Los Gatos, and Hugo series. The Yorkville soils are a heavy clay characterized by landslips and seep areas. Less represented soil series at HREC are the Stonyford and Sobrante series, which formed on localized areas of basalt; Climax, derived from small areas of basalt and sandstone; and the Henneke and Montara series, derived from serpentine rock.
The moderately shallow soils of the Laughlin series are slightly acidic with depths ranging from 1 ft to 3 ft. Distributed throughout the lower elevations of HREC, these soils are on nonsteep to steep, partly rounded slopes. The Laughlin series is characterized by a vegetation cover of grasses with blue oak (Quercus douglasii), with a few areas of dense interior live oak (Quercus wislizenii) coverage.
The Josephine soils are distributed throughout the station and occur on nonsteep to steep slopes, most of which face toward the north or east. Surface soils are slightly acidic, subsurface soils are moderately acidic. Soil depths range from less than 36 inches to more than 60 inches. Typical vegetation of this soil is moderate to dense hardwoods with some shrubs and conifers. Dominant plants are black oak (Quercus kelloggii), madrone (Arbutus menziesii), and Douglas fir (Pseudotsuga menziesii).
Sutherlin soils, widely distributed on HREC, have developed from hard sandstone and shale and are typically grass-covered with scattered blue oaks and interior live oaks. Soil depth is usually less than 3 ft and surface soils are slightly acid. These soils are on nonsteep to steep rounded slopes.
Distinguished by landslips and seep areas, Yorkville soils occur across HREC on steep to nonsteep slopes. These are heavy clays with grass cover and blue oaks and valley oaks (Q. lobata) on stable areas.
Hugo soils are shallow soils (less than 36 inches in depth) that are slightly acidic and generally gravelly. These soils occur on rather steep north or east exposures. The few areas of Hugo soil at HREC occur in the northeastern portion of the Center, in upper James I and James III pastures. Native vegetation typical of this soil type is a dense cover of hardwood with some shrubs and conifers. Dominant plants are black oak, madrone, California buckeye (Aesculus californica), and Douglas fir.
Los Gatos series soils are rocky, generally steeply sloping, moderately acidic throughout, and shrub-covered. Most of these soils are found at the higher elevations of HREC and have depths of 12-24 inches. The dominant shrubs on this soil type are chamise (Adenostoma fasciculatum), wedgeleaf ceanothus (Ceanothus cuneatus), common manzanita (Arctostaphylos manzanita), eastwood manzanita (Arctostaphylos glandulosa), wavyleaf ceanothus (Ceanothus foliosus), and shrub interior live oak (Quercus wislizenii var. frutescens).
The soils of the Maymen series are typically shallow, steep, stony, and shrub-covered. Moderately acidic throughout, these soils are associated with rock outcrops and occur primarily at the higher elevations of HREC, in James I, James II, James III, and Orchard pastures and Riley Ridge Biological Area. Native vegetation on these soils consists of moderate to dense shrub cover of chamise and wedgeleaf ceanothus.
Serpentine soils are present at HREC and should be addressed because of the unique associated vegetation. Kruckeberg (1984) describes serpentine as a type of ultramafic rock in which iron and magnesium are chief elements. In California, these largely occur in the foothills of the Sierra Nevada and the Coast Ranges from San Luis Obispo County north to the Oregon border. Serpentine rock weathers to soils rich in magnesium, iron, silicates, and often exceptional amounts of nickel. The typical clay mineral is smectite (montmorillonite), which has a large shrink-swell capability. Serpentine soils have high values of exchangeable magnesium and exceptionally low values of exchangeable calcium. They are usually deficient in nitrogen and phosphorus, and can attain high values of heavy metals (esp. iron and nickel) in both soils and plant tissues. Kruckeberg (1984) mentions several factors contributing to the unique vegetation of serpentine soils: the imbalance of calcium and magnesium, magnesium toxicity, heavy metal toxicity, or low levels of essential nutrients. Drought stress, in addition to chemical imbalance, causes severe environmental conditions, thus the striking discontinuity between vegetation on serpentine soil and adjacent non-serpentine soil. In California, the vegetation change is often from oak woodland to chaparral, or chaparral to sparse grassland.
At HREC, the Montara and Henneke soil series are derived from serpentine rock. These soils occur in rather small units at higher elevations in the north central portion of HREC in Orchard pasture (Henneke) and a few small areas in the lower elevations (Montara) in the Foster, Watershed II, Vasser, West Vasser, and South pastures. The Montara series and more open Henneke areas have a grass cover of primarily the invasive barbed goat grass (Aegilops triuncialis). The rest of the Henneke area has a moderately dense to nearly open shrub cover including hoary manzanita (Arctostaphylos canescens), leather oak (Quercus durata, serpentine endemic), chamise, and Sargent cypress (Cupressus sargentii, serpentine endemic).
The most notable geologic formation on HREC is the Mayacama fault line which runs the length of the Center, southeast to northwest. Implications of this fault activity are that parts of the eastern portion of HREC are prone to landslides. The Alquist-Priolo Special Studies Zones maps in HREC library show locations of current and potential landslides. Seismic activity of the Mayacama fault line is monitored by the automated University of California-Berkeley seismic station located in Watershed I pasture.