Tree Dominated Wildlife Habitats
Valley Foothill Riparian
(VRI) Cottonwood, Sycamore, Valley Oak
Vegetation
Structure-- Canopy height is approximately 30 m (98 ft) in a mature riparian forest, with a canopy cover of 20 to 80 percent. Most trees are winter deciduous. There is a subcanopy tree layer and an understory shrub layer. Lianas (usually wild grape) frequently provide 30 to 50 percent of the ground cover and festoon trees to heights of 20 to 30 m (65 to 98 ft). Herbaceous vegetation constitutes about one percent of the cover, except in openings where tall forbs and shade-tolerant grasses occur (Conard et al. 1977). Generally, the understory is impenetrable and includes fallen limbs and other debris.
Composition-- Dominant species in the canopy layer are cottonwood, California sycamore and valley oak. Subcanopy trees are white alder, boxelder and Oregon ash. Typical understory shrub layer plants include wild grape, wild rose, California blackberry, blue elderberry, poison oak, buttonbrush, and willows. The herbaceous layer consists of sedges, rushes, grasses, miner's lettuce, Douglas sagewort, poison-hemlock, and hoary nettle.
Other Classifications-- Other classification schemes that describe VRI habitats are Cottonwood and California Sycamore (Parker and Matyas 1981), Central Valley Bottomland Woodland 6.11, Southern Alluvial Woodland - 6.31 (Cheatham and Haller 1975), Wild Rose Alder, Cottonwood, Sycamore, Willow (Paysen et al. 1980), Riparian Forest - 28 (Küchler 1977) and Forested Wetland -61 (Anderson et al. 1976).
Habitat Stages
Vegetation Changes-- 1;2-5:S-D. Cottonwoods grow rapidly and can reach WHR size/age class 5 in about 20 to 25 years. One specimen measuring 92 cm (36 in) (inside the bark) showed an age of 29 years (Sudworth 1908). This secondary succession to climax could occur as rapidly as 25 to 30 years in VRI habitats dominated by cottonwood. One valley oak tree 54 cm (21 in) in diameter (WHR size/age class 4) showed an age of 57 years. Valley oak dominated riparian systems would probably take 75+ years to reach climax/maturity. Some VRI types consisting of only a shrub layer (VRI 1;2: S-D) (willows, wild rose, blackberry) may persist indefinitely. Duration of Stages-- Shrubby riparian willow thickets may last 15-20 years before being overtopped and shaded out by cottonwoods. Cottonwood or willow tree habitats close to river channels that receive a good silt infusion, without major disruptive flows, tend to be self perpetuating (R. Holland pers. comm.).
Biological Setting
Habitat-- Transition to adjacent non-riparian vegetation is usually abrupt, especially near agriculture (Cheatham and Haller 1975). The Valley-Foothill Riparian habitat is found in association with Riverine (RIV), Grassland (AGS, PGS), Oak Woodland (VFH) and Agriculture (PAS, CRP). It may intergrade upstream with Montane
Riparian.
Wildlife Considerations-- Valley-foothill riparian habitats provide food, water, migration and dispersal corridors, and escape, nesting, and thermal cover for an abundance of wildlife. At least 50 amphibians and reptiles occur in lowland riparian systems. Many are permanent residents, others are transient or temporal visitors (Brode and Bury 1985). In one study conducted on the Sacramento River, 147 bird species were recorded as nesters or winter visitants (Laymon 1985). Additionally, 55 species of mammals are known to use California's Central Valley riparian communities (Trapp et al. 1985).(No 1985 cites for Brode and Bury, Laymon, and Trapp et al. in habitat Lit Cite. I used 1984 cites for all 3 in Lit Cite at end.)
Physical Setting
Valley-foothill riparian habitats are found in valleys bordered by sloping alluvial fans, slightly dissected terraces, lower foothills, and coastal plains. They are generally associated with low velocity flows, flood plains, and gentle topography. Valleys provide deep alluvial soils and a high water table. The substrate is coarse, gravelly or rocky soils more or less permanently moist, but probably well aerated (Cheatham and Haller 1975). Average precipitation ranges from 15 to 76 cm (6-30 in), with little or no snow. The growing season is 7 to 11 months. Frost and short periods of freezing occur in winter (200 to 350 frost-free days). Mean summer maximum temperatures are 24 to 39 C (75 to 102 F), mean winter minima are 2 to 7 C (29 to 44 F) (Munz and Keck 1973). VRI habitats are characterized by hot, dry summers, mild and wet winters. Coastal areas have a more moderate climate than the interior and receive some summer moisture from fog (Bailey 1980). Potential evaporation during the warmest months is often greater than precipitation. Low rainfall and streamflow result in water scarcity in many parts of the area.
Distribution
Valley-foothill riparian habitats occur in the Central Valley and the lower foothills of the Cascade, Sierra Nevada and Coast ranges. They are also found in lower slopes at the bases of the Peninsular and Transverse ranges. A few lower elevation locations are on the desert side of the southern California mountains. VRI habitats range from sea level to 1000 m (3000 ft), fingering upward to 1550 m (5000 ft) on south-facing slopes.
Literature Cited
Anderson, J. R., E. E. Hardy, J. T. Roach, and R. E. Witmer. 1976. A land use and land cover classification system for use with remote sensor data. U.S. Dep. Interior, Geol. Surv., Prof. Pap. 964.
Bailey, R. 1980. Descriptions of ecoregions of the United States. U.S. Dep. Agric., For. Serv., Misc. Publ. 1391.
Brode, J., and R. B. Bury.1984. The importance of riparian systems to amphibians and reptiles. Pages 30-36 in R. E. Warner and K. Hendrix, eds. California riparian systems: ecology, conservation, and productive management Univ. of California Press, Berkeley.
Cheatham, N. H., and J. R. Haller. 1975. An annotated list of California habitat types. Univ. of California Natural Land and Water Reserve System, unpubl. manuscript Conard, S., R. McDonald, and R. Holland. 1977. Riparian vegetation and flora of the Sacramento Valley. Pages 47-55 In A. Sands, ed. Riparian forests in California: their ecology and conservation. Univ. of California, Davis, Inst. of Ecol. Publ. No. 15.
Kuchler, A. W. 1977. Appendix: the map of the natural vegetation of California. Pages 909-938 In M. G. Barbour and J. Major, eds, Terrestrial vegetation of California. John Wiley and Sons, New York.
Laymon, S. A.1984. Riparian bird community structure and dynamics: Dog Island, Red Bluff, California, Pages 587-597 In R. E. Warner and K. M. Hendrix, California riparian systems: ecology, conservation and productive management. Univ. of California Press, Berkeley.
Munz, P. A., and D. D. Keck. 1973. A California flora with supplement. Univ. of California Press, Berkeley.
Parker, I., and W. J. Matyas. 1981. CALVEG: a classification of Californian vegetation. U.S. Dep. Agric., For. Serv., Reg. Ecol. Group, San Francisco.
Paysen, T. E., J. A. Derby, H. Black, Jr., V. C. Bleich, and J. W. Mincks. 1980. A vegetation classification system applied to southern California. U.S. Dep. Agric., For. Serv., (Berkeley, Calif.) Gen. Tech. Rep. PSW-45. Sudworth, G. B. 1908. Forest trees of the Pacific slope. U.S. Govt. Printing Office.
Trapp, G. R., G. L., Linck, and E. D. Whisler. 1984. The status of ecological research on the mammal fauna of California's central valley riparian communities. Pages 942- 949 In R. E. Warner and K. Hendrix, eds. California riparian systems: ecology, conservation, and productive management. Univ. of California Press, Berkeley.
California Wildlife Habitat Relationships System, California Department of Fish and Game, California Interagency Wildlife Task Group, Valley Foothill Riparian - William E. Grenfell Jr.
Mourning Dove - Desert Wildlife In California, 3 to more than 40 pairs nest per 40 ha (100 ac) in valley foothill hardwood and valley foothill riparian habitats (VanVelzen 1974). ...
Western Whiptail Lizard, Aspidoscelis tigris The western whiptail occurs in a variety of habitats including valley-foothill hardwood, valley-foothill hardwood-conifer, valley-foothill riparian, ...
Sierra Nevada Ecological Subsections Sierran foothills contain some of the densest year-round prehistoric habitation locations in California, particularly along riparian areas, where intensive ...
Roadrunner - Desert Wildlife ... and valley foothill hardwood and montane hardwood-conifer habitats. ... Breeding birds of desert riparian habitat in southern Nevada. Condor 72:431-436. ...
Whiptail Lizard - Desert Wildlife The western whiptail occurs in a variety of habitats including valley-foothill hardwood, valley-foothill hardwood-conifer, valley-foothill riparian, ...
Western Scrub Jay - Birds, Wildlife in the Mojave Desert Frequents scrub habitats, especially with oaks; chaparral, coastal scrub, hardwood, hardwood-conifer, valley foothill riparian, pinyon-juniper, and urban. ...
Costa's Hummingbird - Birds, Wildlife in the Mojave Desert Primary habitats are desert wash, edges of desert riparian and valley foothill riparian, coastal scrub, desert scrub, desert succulent shrub, ...
Loggerhead Shrike - Birds, Wildlife in the Mojave Desert Highest density occurs in open-canopied valley foothill hardwood, valley foothill hardwood-conifer, valley foothill riparian, pinyon-juniper, juniper, ...
Kingsnake Widely distributed, and occurring in nearly all habitats (exclusive of high mountains), the common kingsnake is most abundant in valley-foothill riparian ...
Great Horned Owl - Birds, Wildlife in the Mojave Desert Commonly feeds and breeds in riparian, conifer, chaparral, and desert habitats. ... Predation by owls in the sierran foothills of California. ...
