A Hardwood Rangeland Classification System for California
An ecologically-based hardwood rangeland classification system for California provides private landowners, land managers, and researchers a unifying framework from which known ecological and management information can be retrieved. Standardization of type names facilitates the exchange of information on hardwood rangelands between and among agencies, landowners, and universities. As part of research funded by the Integrated Hardwood Range Management Program, dichotomous keys have been developed for the various type descriptions to ensure that the system is field oriented, and user-friendly. Ongoing research, where sites are labelled using the classification system, will eventually provide information on site response to management treatments.
The Approach to Classification
The classification system was developed from approximately 4300 field plots collected as part of the Vegetation Type Map (VTM) survey conducted during 1919-1940's by the USDA Forest Service Pacific Southwest Station. The base information on species composition, percent cover by species, tree stand structure and environment was collected on 1/5 acre plots. Species cover was determined from a 33 foot wide belt on each plot.
The classification system was designed to be user friendly. At a site, the user can use the appropriate key to determine the type, and read the type description to determine if the information provided in the description matches what the user is observing. The keys and type descriptions have been field tested and verified at several locations in the State, such as Hopland Field Station, Sierra Field Station, Hastings Reserve, and the San Joaquin Experimental Range. The tests were conducted by individuals familiar with hardwood rangeland ecosystems and those who were not.
The oak woodlands of California have been divided into 57 subseries arranged within 7 series defined by the dominant oak species. There are 15 subseries in the Coast Live Oak Series, 12 subseries within the Blue Oak Series, 6 subseries in the Valley Oak Series, 6 subseries in the Interior Live Oak Series, 13 subseries within the Black Oak Series and 3 subseries within the Scrub Oak Series. A Mixed Oak Series is described for which there are 3 or more species of oak occupying 30 percent of the total cover. There are 11 subseries in this Mixed Oak Series.
The convention followed for naming oak woodland cover types uses the dominant species of the tree, shrub, or herbaceous layer. The oak species with the greatest constancy across all plots representing the type is used in the name. A slash (/) is used to separate species of different life forms, and a dash (-) is used to separate species of the same life form, for examples Coast Live Oak/Ocean Spray-Snowberry and Blue Oak-Foothill Pine/Grass. The species code used for each species is from the national standard list of codes, summarized by Robert Powell (1987) for California. The first two letters of the code are the first two letters of the genus, while the second two letters are the first two letters of the species. For example, QUAG/HODI-SYRI would be Coast Live Oak (Quercus agrifolia)/Creambush (Holodiscus discolor) - Snowberry (Syphoricarpus ribularis).
The keys to the oak cover types were constructed using both dominant species and species that indicate differences in environments between types. Attributes of the types that are easily recognizable in the field were used in the keys. Users must be able to recognize approximately a dozen plant species in the field to use the keys.
Table 1 contains the Coast Live Oak Series key as an example. The first division in the key separates the Coast Live Oak type from the others based on its high basal area and lack of understory species. The other 14 subseries are further divided in the key into mesic (moist) and xeric (dry) types. Species that characterize the mesic subseries include: bracken fern (Pteridium aquilinum) in the herb layer; coffeeberry (Rhamnus californica), creambush (Holodiscus discolor), snowberry (Symphoricarpus mollis), and hazelnut (Corylus cornuta) in the shrub layer; and finally in the tree layer, big-leaf maple (Acer macrophyllum), California bay (Umbellularia californica), madrone (Arbutus menziesii), and scrub oak (Quercus dumosa).
In the xeric subseries, species in theshrub layer commonly include toyon (Heteromeles arbutifolia), chamise (Adenostema fasciculatum), coast sagebrush (Artemisia californica), and/or black sage (Salvia mellifera). Xeric types generally contain only oaks in the tree layer.
An example type description is provided in Table 2 for the Coast Live Oak/Blackberry/Bracken Fern subseries. This subseries may contain madrone, California bay, Douglas-fir (Pseudotsuga menziesii), or interior live oak in addition to coast live oak. Common understory species include poison oak (Rhus diversiloba), blackberry (Rubus sp.), baccharis (Baccharis pilularis), and creambush. The type occurs in the central Coast Ranges on all slopes and aspects. This type was described by McBride (1974) in his successional study of Q. agrifolia dominated woodlands in the Berkeley Hills. He suggested that in this locale coast live oak woodland is the last seral stage before a California bay community as a climax type.
Similar descriptions and keys (Tables 1 and 2) are available for all 57 oak habitat subseries in the state. The classification system is titled, Rangeland Cover Type Descriptions for California's Hardwood Rangelands, and is available from the California Department of Forestry and Fire Protection, FRRAP staff at 1416 Ninth St., Sacramento, CA 94244-2460.
The classification system will be used by researchers and other users to label field sites, and thus serve as a tool to organize information about site response to various land treatments. The type descriptions will be updated periodically as new research provides information on site response to burning, harvesting, regeneration success, livestock grazing response, wildlife occupancy, and other activities. The classification system itself is just a tool, an ecologically-based way of organizing complex information about oak woodlands.
Table 1. Key to the Coast Live Oak Subseries (Allen et al. 1990).
1a. Coast live oak (QUAG) is the only overstory tree. Understory species are rarely present with total cover that seldom exceeds 25 percent. Coast live oak basal area is usually high (>200 ft2/acre).
Coast Live Oak
1b. Coast live oak may be the only overstory tree present and total understory cover exceeds 25 percent. Coast live oak basal area is less than 200 ft2/acre.
2a. Understory grass cover generally exceeds 50 percent.
3a. Blue oak is present.
Blue Oak-Coast Live Oak/Grass
3b. Blue oak is absent.
Coast Live Oak/Grass
2b. Understory grass cover is less than 50 percent.
4a. The following shrubs are present individually or together in the understory: coffeeberry, ocean spray, blackberry, and hazelnut. Big leaf maple may be present in the tree layer. The shrubs toyon, chamise, coast sagebrush, and black sage are absent. California bay is absent.
5a. Bracken fern is present, baccharis is often present. Big leaf maple, madrone, snowberry and hazelnut are absent.
Coast Live Oak/Blackberry/Bracken Fern
5b. Bracken fern and baccharis are absent.
6a. Madrone and hazelnut are present. Big leaf maple, ocean spray and snowberry are absent.
Coast Live Oak-Madrone/Hazelnut-Blackberry
6b. Madrone and hazelnut are absent. Big leaf maple, ocean spray and snowberry are present.
7a. Big leaf maple is present. Snowberry is absent.
Coast Live Oak-Maple/Coffeeberry-Ocean Spray
7b. Big leaf maple is absent. Snowberry is present.
Coast Live Oak/Ocean Spray-Snowberry
4b. Blackberry, hazelnut, and big leaf maple are absent. Coffeeberry and ocean spray may be present. The shrubs toyon, chamise, coast sagebrush, and black sage may be present. California bay may be present.
8a. Toyon is present. Redberry and California bay may be present. Black sage and coast sagebrush are absent.
9a. Other shrubs and trees are generally absent.
Coast Live Oak/Toyon-Poison Oak
9b. Coffeeberry, redberry, ocean spray, and California bay may be present. Chamise and wedgeleaf ceanothus may be present.
10a. Chamise is present; wedgeleaf ceanothus is often present. Coffeeberry, ocean spray, and California bay are absent.
Coast Live Oak/Toyon/Grass
10b. Chamise and wedgeleaf ceanothus are absent. Coffeeberry, redberry and California bay are present.
11a. Coffeeberry and redberry are present. California bay and scrub oak are absent.
Coast Live Oak/Coffeeberry-Toyon
11b. Coffeeberry and redberry are absent. California bay and scrub oak are present.
Coast Live Oak-California Bay/Toyon-Scrub Oak
8b. Toyon is absent. Redberry and California bay are absent. Black sage and coast sagebrush may be present.
12a. Chamise, black sage and coast sagebrush are present individually or together.
13a. Coast sagebrush is present with greater than 25% cover of grasses. Chamise and black sage are absent.
Coast Live Oak/Coast Sagebrush/Grass
13b. Coast sagebrush is absent. Chamise and black sage are present individually or together with less than 25% cover of grasses.
Coast Live Oak/Chamise-Black Sage
12b. Chamise, black sage and coast sagebrush are absent.
14a. Poison oak is the dominant shrub cover. Grass cover is absent.
Coast Live Oak/Poison Oak
14b. Poison oak and grass both have high cover.
Coast Live Oak/Poison Oak/Grass
Table 2. Subseries description for the Coast Live Oak/Blackberry/ Bracken Fern oak subseries. This description is one of 57 similar descriptions that can be found in Allen et al.(1990).
Coast Live Oak/BlackberryBracken Fern
Location: This type occurs in the central coast ranges from Contra Costa to Santa Cruz County.
Elevation: Mean: 783 ft; Ranges from 200 to 2000 ft.
Aspect: All aspects.
Slope: All slopes.
Parent Material: Hard and soft sedimentary rocks.
Soil Texture: Sandy and gravelly loams.
RELATIONSHIPS TO OTHER CLASSIFICATIONS:
Cheatham and Haller (1975): Coast Live Oak Forest
Griffin (1977): Southern Oak Woodland, QUAG phase.
Holland (1986): Coast Live Oak Woodland
Parker and Matyas (1981): Coast Live Oak
Paysen et al. (1980): Coast Live Oak
Mayer et al. (1988): Coastal Oak Woodland
VEGETATION COVER SUMMARY OF DOMINANTS
|Tree Overstory||Basal Area (sq. ft./ac)|
|QUAG Coast live oak||18||2-92||94|
|QUAG Coast live oak||3||0-5||24|
|RHDI Poison oak||14||0-28||76|
|HODI Ocean spray||18||0-59||53|
|CETH Blueblossom ceanothus||17||0-49||41|
|PTAQ Bracken Fern||13||0-42||82|
STAND TABLE: Relative number of trees by diameter class (in inches) by species. For any diameter class, the mean number of trees per diameter class, the standard deviation (SD), and the number (N) of plots out of the total number of plots used to describe the subseries is noted.