Ceanothus (oliganthus, tomentosus) Shrubland Alliance
Hairy leaf - woolly leaf ceanothus chaparral
Hairy leaf - woolly leaf ceanothus chaparral
USDA Ecological Section Map
Summary Information
- Primary Life FormShrub
- Elevation40-1500 m
- State RarityS3
- Global RarityG3
- DistributionUSA: CA (NatureServe) (Calflora), Baja California, Mexico (TJM2)
- Endemic to CaliforniaNo
- Endemic to California Floristic Province and DesertsYes
- Date Added1995/11/01
Characteristic Species
Ceanothus oliganthus or Ceanothus tomentosus is dominant or co-dominant in the shrub canopy with Adenostoma fasciculatum, Adenostoma sparsifolium, Arctostaphylos glandulosa, Ceanothus megacarpus, Heteromeles arbutifolia, Quercus berberidifolia, Rhus ovata, Salvia mellifera, Toxicodendron diversilobum or Xylococcus bicolor. Emergent trees may be present at low cover, including Calocedrus decurrens, Juglans californica, Pseudotsuga macrocarpa, Quercus agrifolia, Quercus chrysolepis, Quercus wislizeni or Umbellularia californica.
Vegetation Layers
Shrubs < 4 m; canopy is continuous to intermittent. Herbaceous layer is sparse.
Membership Rules
- Ceanothus oliganthus > 60% relative cover in shrub canopy (Borchert et al. 2004, Evens and San 2005, Klein and Evens 2005).
- Ceanothus tomentosus > 30% relative cover in the shrub canopy with Malosma laurina, Adenostoma fasciculatum, and Xylococcus bicolor subdominant if present (Sproul et al. 2011).
- Ceanothus cyaneus > 50% relative cover in the shrub canopy, or > 30% relative cover with > 50% Ceanothus spp. (Sproul et al. 2011).
- Ceanothus leucodermis or Ceanothus oliganthus > 50% relative cover in the shrub canopy that are often found in localized patches following fires (Sikes et al. 2023).
Habitats
Variable topography. Soils are moderately deep and well drained.
Other Habitat, Alliance and Community Groupings
| MCV (1995) | Hairyleaf ceanothus series |
| NVCS (2009) | Ceanothus oliganthus shrubland alliance |
| Calveg | Ceanothus chaparral |
| Holland | Northern mixed chaparral, Southern mixed chaparral, Mixed montane chaparral, Upper Sonoran ceanothus chaparral, Mesic north slope chaparral |
| Munz | Chaparral |
| WHR | Mixed chaparral |
| CDFW CA Code | 37.207.00 |
National Vegetation Classification Hierarchy
| Formation Class | Mesomorphic Shrub and Herb Vegetation (Shrubland and Grassland) |
| Formation Subclass | Mediterranean Scrub and Grassland |
| Formation | Mediterranean Scrub |
| Division | California Scrub |
| Macro Group | California Chaparral |
| Group | Californian pre-montane chaparral |
Remarks
Ceanothus oliganthus is an evergreen shrub with rigid branches that grows to 6 m in height. At 5 years, shrubs begin producing seed, which is explosively cast from plants as their capsules break. Most of the seed drops beneath the crowns of the shrubs. Seed predation by small mammals and insects may be severe, but with time, seeds collect in the duff and soil as a seed bank. Ceanothus oliganthus rapidly sprouts from root crowns when branches are removed.
Ceanothus oliganthus includes three varieties. Var. orcuttii is limited to the Peninsular Ranges of southern California and adjacent Baja California. It is distinguished from the other varieties by its short-hairy flower parts and wrinkled fruits (Wilken and Burge 2016). The other two varieties are separated on stem and leaf pubescence: var. oliganthus is called hairy leaf ceanothus and var. sorediatus is called Jim brush. Jim brush has a more northern range, but ranges overlap in the Los Padres National Forest (Borchert et al. 2004) and further south. The species is ecologically and morphologically similar to C. tomentosus and therefore they are included in a single alliance.
Ceanothus tomentosus is an evergreen shrub that grows to nearly 3 m in height. The leaves are dark green adaxially and typically woolly underneath. This species typically grows at lower elevations with less winter frost than does C. oliganthus.
Stands of C. oliganthus or C. tomentosus tend to occur as small, localized patches after recent fire disturbance, and they senesce after about 30-40 years. Stands occur on northerly slopes and adjacent to riparian areas in southern California, and they occur on a wide range of slopes and exposures in central California.
This alliance has been expanded to include additional Ceanothus species of the subgenus Ceanothus since the 2009 publication of A Manual of California Vegetation, second edition.
Ceanothus oliganthus includes three varieties. Var. orcuttii is limited to the Peninsular Ranges of southern California and adjacent Baja California. It is distinguished from the other varieties by its short-hairy flower parts and wrinkled fruits (Wilken and Burge 2016). The other two varieties are separated on stem and leaf pubescence: var. oliganthus is called hairy leaf ceanothus and var. sorediatus is called Jim brush. Jim brush has a more northern range, but ranges overlap in the Los Padres National Forest (Borchert et al. 2004) and further south. The species is ecologically and morphologically similar to C. tomentosus and therefore they are included in a single alliance.
Ceanothus tomentosus is an evergreen shrub that grows to nearly 3 m in height. The leaves are dark green adaxially and typically woolly underneath. This species typically grows at lower elevations with less winter frost than does C. oliganthus.
Stands of C. oliganthus or C. tomentosus tend to occur as small, localized patches after recent fire disturbance, and they senesce after about 30-40 years. Stands occur on northerly slopes and adjacent to riparian areas in southern California, and they occur on a wide range of slopes and exposures in central California.
This alliance has been expanded to include additional Ceanothus species of the subgenus Ceanothus since the 2009 publication of A Manual of California Vegetation, second edition.
Life History Traits of the Principal Species
| Ceanothus oliganthus | Ceanothus tomentosus | |
|---|---|---|
| Life forms | Shrub; evergreen | Shrub; evergreen |
| Seed storage | Soil | Soil |
| Seed longevity | Long | Long |
| Mode of dispersal | Animal; expulsion from capsule | Animal; Expulsion from capsule |
| Germination agents | Heat | Heat |
| Mode of sprouting | Buds on large branches or trunks; underground structures (root crown) | Buds on small branches; Underground structures |
| Survivability after fire/disturbance | Fire-hardy; high sprouter | Fire-sensitive |
| Disturbance-stimulated flowering | No | Unknown |
| Reproductive range | ?(40?)-100? years (to life of plant?) | 4? - 50 years |
| Recruitment | Episodic | Episodic |
| Regional variation | Low | Low |
Fire Characteristics
Ceanothus oliganthus is an obligate seeder, in which large numbers of seedlings establish from the seed bank after fire. Heat stimulates seed germination by increasing permeability to water. Dense, monotypic stands can develop and then self-thin with > 50% of the shrubs dying, especially the smaller ones (Riggan et al. 1988). Mortality continues with stand senescence within 40 years after fire (Hanes 1971). An average fire cycle of 25-50 years should promote C. oliganthus.
| Fire return interval | Medium (25-100 years) |
| Seasonality | Summer-early fall |
| Size/extent | Medium to large; up to and beyond stand |
| Complexity | Low |
| Intensity | High |
| Severity | Very high |
| Type | Active-independent crown fire |
| Regional knowledge | Central California |
Regional Status
- Central California Coast (261Ac, Af-g, Aj-k). Small, isolated stands occur at Cone Peak Gradient RNA (Cheng 2004) and elsewhere in the Santa Lucia Mountains (Borchert et al. 2004). Many of these are the result of crown fires in the past several decades.
- Central California Coast Ranges (M262Aa-b, Ae-f). Small, isolated stands occur in the interior Santa Lucia Mountains and Gabilan Range (Borchert et al. 2004). Stands have also been observed in the East Bay Hills of Alameda and Contra Costa Cos.
- Northern California Coast (263Af-g, Al-m). Stands occur from Marin and Sonoma Cos. north to Humboldt Co.
- Northern California Coast Ranges (M261Ba-b, Bd-f). Stands have been observed from Napa north to Humboldt Co.
- Northern California Interior Coast Ranges (M261Ca). Stands are common in the Vaca Mountains and in Napa and Yolo Cos.
- Southern California Coast (261Ba-b, Be-f, Bi). Small, isolated stands are found in the Santa Ynez Mountains on all aspects up to 1200 m (Borchert et al. 2004). In the Santa Monica Mountains (Keeler-Wolf and Evens 2006), stands are typically restricted to concave, north-facing slopes above 800 m.
- Southern California Mountains and Valleys (M262Ba-d, Bf-g, Bk-l, Bn-o). Stands are widely distributed but usually localized. Stands in the San Gabriel Mountains (Gordon and White 1994), the western Transverse Ranges (Borchert et al. 2004), San Diego Co. (Evens and San 2005), and western Riverside Co. (Klein and Evens 2005) are typically restricted to north-facing slopes above 350 m. Stands in the Volcan Mountain area formed a dense canopy of young shrubs upon 3 years after the 2002 Pines fire. Most are associated with burned stands of Pseudotsuga macrocarpa-Quercus chrysolepis alliance. Prior to the fire, C. oliganthus was not apparent in the understory of most of these stands.
Management Considerations
Repeated short-interval fires (of < 25 years) deplete the seed bank. The genus is well suited for use in rehabilitation because of rapid growth rates and an ability to improve soil fertility through fixing nitrogen.
Associations
- Ceanothus cyaneus [6]
- Ceanothus oliganthus [1], [3], [4], [7], [9], [10]
- Ceanothus oliganthus - Adenostoma fasciculatum [5]
- Ceanothus oliganthus - Adenostoma fasciculatum - Xylococcus bicolor [2]
- Ceanothus oliganthus - Adenostoma sparsifolium [4]
- Ceanothus oliganthus - Arctostaphylos glandulosa [5]
- Ceanothus oliganthus - Eriodictyon crassifolium [5]
- Ceanothus oliganthus - Heteromeles arbutifolia - Rhus ovata [4]
- Ceanothus oliganthus - Quercus berberidifolia [4]
- Ceanothus tomentosus [3], [6], [8]
References
- [1] Borchert, M.;Lopez, A.;Bauer, C.;Knowd, T. 2004
- [2] Evens, J.;San, S. 2005
- [3] Gordon, H.J.;White, T.C. 1994
- [4] Keeler-Wolf, T.;Evens, J. 2006
- [5] Klein, A.;Evens, J. 2005
- [6] Sproul, F.;Keeler-Wolf, T.;Gordon-Reedy, P.;Dunn, J.;Klein, A.;Harper, K. 2011
- [7] Klein, A.;Keeler-Wolf, T.;Evens, J. 2015
- [8] AECOM, 2013
- [9] Reyes, E.;Johnson, D.;Glass, A. 2019
- [10] Sikes, K.;Buck-Diaz, J.;Vu, S.:Evens, J. 2023
- Barry, W.J. 1989a
- Barry, W.J. 1989b
- Hanes, T.L. 1977
- Hanes, T.L. 1981
- Keeley, J.E.;Keeley, S.C. 1988
- Pase, C.P. 1982a
- Paysen, T.E.;Derby, J.A.;Black, H.;Bleich, V.C.;Mincks, J.W. 1980
- Shiflet, T.N. 1994
- Thorne, R.F. 1976
- White, S.D. 1994c