Quercus engelmannii Forest & Woodland Alliance
Engelmann oak woodland and forest
Engelmann oak woodland and forest
USDA Ecological Section Map
Summary Information
- Primary Life FormTree
- Elevation50-1220 m
- State RarityS3
- Global RarityG3
- DistributionUSA: CA. Baja California, Mexico (TJM2)
- Endemic to CaliforniaNo
- Endemic to California Floristic Province and DesertsYes
- Date Added1995/11/01
Characteristic Species
Quercus engelmannii is dominant or co-dominant in the tree canopy with Juglans californica, Quercus agrifolia and Quercus kelloggii.
Vegetation Layers
Trees < 18 m tall; canopy is open (greater than 10%) to continuous, or savanna-like (less than 10%, but evenly distributed). Shrub layer is sparse to intermittent. Herbaceous layer is sparse or grassy.
Membership Rules
- Quercus engelmannii > 30% relative cover in the tree canopy (Evens and San 2005, Klein and Evens 2005).
Habitats
Raised stream terraces along stream corridors, valley bottoms, and gentle lower slopes.
Other Habitat, Alliance and Community Groupings
| MCV (1995) | Engelmann oak series |
| NVCS (2009) | Quercus engelmannii woodland alliance |
| Calveg | Engelmann oak |
| Holland | Open Engelmann oak woodland, Dense Engelmann oak woodland |
| Munz | Southern oak woodland |
| WHR | Coastal oak woodland |
| CDFW CA Code | 71.070.00 |
National Vegetation Classification Hierarchy
| Formation Class | Mesomorphic Tree Vegetation (Forest and Woodland) |
| Formation Subclass | Temperate Forest |
| Formation | Warm Temperate Forest |
| Division | Madrean Forest and Woodland |
| Macro Group | California Forest and Woodland |
| Group | Californian broadleaf forest and woodland |
Remarks
Quercus engelmannii attains 18 m in height and 350 years in age. Leaves have a bluish color and are semi-deciduous. Trees mast on irregular cycles, and acorns develop in a year. Birds and small mammals disperse and cache the acorns. Germination and seedling establishment are dependent on the availability of shade (Pavlik et al. 1991, Scott 1990). Q. engelmannii is a CNPS list 4 plant. It hybridizes with Q. berberidifolia, and intermediate plants are common on margins between oak shrubland and woodland stands. It also hybridizes with Q. cornelius-mulleri with stable hybrids called Q. xacutidens.
Quercus engelmannii woodlands cover approximately 14,000 ha mostly in the Peninsular Ranges of southern California (Scott 1991). Q. engelmannii belongs to a distinctive group of mostly Mexican species with a unique seed morphology and germination syndrome that may adapt them to fire or drought. An understanding of this unusual germination ecology may be important in understanding the ecological parameters controlling the distribution of Q. engelmannii in California (Nixon 2002). This oak commonly mixes with Q. agrifolia. If Q. agrifolia is > 60% relative cover in mixed stands, then they are members of the Quercus agrifolia alliance.
Quercus engelmannii woodlands cover approximately 14,000 ha mostly in the Peninsular Ranges of southern California (Scott 1991). Q. engelmannii belongs to a distinctive group of mostly Mexican species with a unique seed morphology and germination syndrome that may adapt them to fire or drought. An understanding of this unusual germination ecology may be important in understanding the ecological parameters controlling the distribution of Q. engelmannii in California (Nixon 2002). This oak commonly mixes with Q. agrifolia. If Q. agrifolia is > 60% relative cover in mixed stands, then they are members of the Quercus agrifolia alliance.
Life History Traits of the Principal Species
| Quercus engelmannii | |
|---|---|
| Life forms | Tree; drought deciduous |
| Seed storage | Transient |
| Seed longevity | Short |
| Mode of dispersal | Animal |
| Germination agents | None |
| Mode of sprouting | Buds on large branches or trunks; underground structures |
| Survivability after fire/disturbance | Fire-hardy; high sprouter |
| Disturbance-stimulated flowering | No |
| Reproductive range | 20-100+ yrs |
| Recruitment | Low |
| Regional variation | High |
Fire Characteristics
Fire effects of Quercus engelmannii have been studied using controlled burns at the Santa Rosa Plateau Reserve in western Riverside Co. (Principe 2002). Fire reduces the survivorship and growth of juvenile oaks, with seedlings being especially sensitive. Post-fire sprouting and survival depend on both individual oak size and amount of damage. Recent fires in eastern San Diego Co. have had varied effects on Q. engelmannii, including variable mortality in mature trees. Stands with grassy understories tend to suffer minimal damage. Trees in stands with shrubby understories are top-killed, but they may sprout and survive.
| Fire return interval | Medium (30-100+ years) |
| Seasonality | Summer-early fall |
| Size/extent | Medium to large—up to or beyond stand size |
| Complexity | Low |
| Intensity | Low to moderate |
| Severity | Low to high |
| Type | Surface-passive crown |
| Regional knowledge | Ecological and fire characteristics vary |
Regional Status
- Southern California Coast (261Bg, Bi). Small fragmented stands exist in the San Fernando Valley and parts of the Los Angeles Basin along the foothills of the San Gabriel Mountains. A few small stands occur in Orange Co. west of the Santa Ana Mountains.
- Southern California Mountains and Valleys (M262Bf, Bj-l, Bn-p). Stands exist on the Santa Rosa Plateau (Griffin 1977, Griggs 1987, Lathrop and Zuill 1984), at King Creek and Organ Valley RNAs (Cheng 2004), in the Ramona-Santa Ysabel area (Griffin 1977), and in western Riverside Co. (Klein and Evens 2005); stands are diverse in San Diego Co. (Evens and San 2005). Where stands approach the desert margin in San Felipe Valley, they may include semi-desert species such as Senegalia greggii, Aristida purpurea, Ceanothus greggii, Q. cornelius-mulleri, and Ziziphus parryi.
Management Considerations
Much of the original range of this alliance included the Los Angeles Basin. Problems facing managers include lack of sapling recruitment, loss of mature trees because of lowered water tables, and the accumulationof saline runoff. Mature trees are sensitive to overwatering, pruning, grade changes, and asphalt covering their root systems. Feral pigs cause considerable damage (Howard 1992l). Trees can establish through weed control and irrigation (Alpert et al. 1999). Removal of understory herbaceous plants prior to the growing season by fire, or especially by mowing, increases seedling establishment (Principe 2002). In addition, prescribed fires in the late summer or early fall, permit better survival of seedlings, saplings, and sprouts in the wet winter months (Lathrop and Osborne 1991). The California Oak Foundation, Oak Woodlands Conservation Program, and others promote preservation and restoration (Griggs and Golet 2002).
Associations
Stands with a Mixed Tree Canopy
- Quercus engelmannii - Quercus agrifolia / Artemisia californica [1], [2]
- Quercus engelmannii - Quercus agrifolia / chaparral (Adenostoma fasciculatum - Quercus berberidifolia - Rhamnus ilicifolia) [1]
- Quercus engelmannii - Quercus agrifolia / Toxicodendron diversilobum / annual grass [1], [2], [3]
Stands with a Simple Tree Canopy
- Quercus engelmannii / Adenostoma fasciculatum - Arctostaphylos glauca [1]
- Quercus engelmannii / annual grass - herb [1]
- Quercus engelmannii / Quercus berberidifolia [1], [2]
- Quercus engelmannii / Salvia apiana / grass - herb [1]
- Quercus engelmannii / Toxicodendron diversilobum / grass [2]
References
- [1] Evens, J.;San, S. 2005
- [2] Klein, A.;Evens, J. 2005
- [3] Sproul, F.;Keeler-Wolf, T.;Gordon-Reedy, P.;Dunn, J.;Klein, A.;Harper, K. 2011
- AECOM, 2017
- Barbour, M.G. 1988
- Beauchamp, R.M. 1986
- Bowler, P.A. 1989
- Boyd, S.D.;Ross, T.S.;Bramlet, D. 1995
- Brown, D.E. 1982b
- Dunning, C.E.;Paine, T.D.;Redak, R.A. 2002
- Gaman, T.;Casey, K. 2002
- Griffin, J.R. 1977
- Griffin, J.R.;Critchfield, W.B. 1972
- Holstein, G. 1984
- Koenig, W.D.;Knops, J.M. 1997
- Lathrop, E.W.;Osborne, C.D. 1991
- Lathrop, E.W.;Zuill, H.A. 1984
- McCreary, D.D. 1990
- Oberbauer, T.A. 1991
- Pavlik, B.M.;Muick, P.C.;Johnson, S.G.;Popper, M. 1991
- Reiser, C.H. 1994
- Scott, T.A. 1990
- Scott, T.A. 1991
- Snow, G.E. 1973
- Snow, G.E. 1991
- Standiford, R.B. 2002
- Zuill, H.A. 1967