PLS 147 Lecture 9: California Oak (and Conifer) Woodlands
woodland
●Trees and perhaps robust shrubs
●but not at high or low cover
○higher: forest
○lower: savanna
○none: grassland, prairie
●20-70% cover
○light allows full ground layer
●name emphasis on 'big' species (visibly dominant)
blue oak, interior oak, valley oak
Northern and Central Valley: Foothill pine woodland
●scattered trees w/ a more continuous chaparral understory
Sierras: Ponderosa Pine Woodland with grass cover
Central Valley and Southern: Juniper woodland
Oak woodlands
●can range from very high cover (approaching forest) to very low woody cover (more like
savanna)
●mostly two-layered, with high understory cover by herbaceous species (grasses)
○grass cover caries low-intensity fire
Climate
●mostly 60-700m elevation
●Mediterranean climate w/ very dry summer
●soils vary depending on community
California Oaks
●hotspot for oak diversity (20 species in CA, 30+ subspecies)
●Genus Quercus in family Fagaceae
●cover 10% of CA land area (bigger than most of the other communities)
●cascading effects, key habitat for many other species >300 vertebrates and 5000>
insects
Oaks distinguished by 4 features
●fruit (acorn)
●flowers (wind pollinated)
●strong, complex hardwood
●long-lived (several centuries)
False Oaks
●poison oak
●tanoak (close relative)
Communities
Valley Oak Woodland
●tends to be along riparian, can also be up on slopes
●deep alluvial soils
●mostly <500m , up to 1700m
●once was far more extensive, perhaps up to miles on either side of major rivers when
there was more flooding
Major Species in Valley Oak Woodland
●Valley Oak
○deciduous, long-lived, largest, long acorn
●also: california sycamore, black walnut, boxelder, cottonwood, blue oak, interior live oak
(valley oak is a minor player more in riparian, further away it becomes dominant)
Flooding
●riparian and floodplain communities
○valley oak is flood tolerant (not for long time)
○flood helps recruitment of valley oak seedlings most common in years
with plentiful soil
●Valley oaks are most reduced (endangered>)
○only a small fraction left because loss of habitat as it grows along a riparian
area, good for agriculture
Blue Oak Woodland
●higher elevations, can tolerate drier soils than valley
●most abundant oak species/community type
○ "bathtub ring"
●serious recruitment issues
●Quercus douglasii
○summer deciduous, long-lived
○fatter acorn
●other species associates:
○foothill pine, california buckeye, manzanita spp, ceonothus spp
Interior Live Oak
●in patches, throughout & overlapping w/ Blue Oak
●steeper, dryer slopes with shallower soils than blue oak
●often has a foothill pine component
●150 m in north, >900 m in south
Document Summary
But not at high or low cover. Name emphasis on "big" species (cid:840)visibly dominant(cid:841) blue oak, interior oak, valley oak. Scattered trees w/ a more continuous chaparral understory. Can range from very high cover (cid:840)approaching forest(cid:841) to very low woody cover (cid:840)more like savanna(cid:841) Mostly two-layered, with high understory cover by herbaceous species (cid:840)grasses(cid:841) Hotspot for oak diversity (cid:840)20 species in ca, 30+ subspecies(cid:841) Cover 10% of ca land area (cid:840)bigger than most of the other communities(cid:841) Cascading effects, key habitat for many other species >300 vertebrates and 5000> insects. Tends to be along riparian, can also be up on slopes. Once was far more extensive, perhaps up to miles on either side of major rivers when there was more flooding. Also: california sycamore, black walnut, boxelder, cottonwood, blue oak, interior live oak (cid:840)valley oak is a minor player more in riparian, further away it becomes dominant(cid:841) Valley oak is flood tolerant (cid:840)not for long time(cid:841)
