Plant Communities
Plant communities of the Blue Oak Ranch include blue oak woodland, valley oak woodland, black oak woodland, coast live oak woodland, riparian forest, chamise chaparral, Diablan sage scrub, nonnative annual grassland, wildflower field, and native perennial grassland (Bainbridge and Kan, 1997). Four of these are threatened plant communities; valley oak woodlands, blue oak woodlands, wildflower field, and native perennial grasslands. Streams on the ranch support healthy stands of riparian vegetation in addition to aquatic species. They are important habitat for migratory birds, and may be migratory corridors for numerous aquatic and terrestrial animal species. The steep slopes of the Arroyo Hondo canyon provide an excellent contrast of vegetation, with the north and east-facing slopes supporting vegetation adapted to relatively cool, moist environments, and the west and south-facing slope vegetation (including chamise chaparral) adapted to hot, dry conditions.
Grasses
Patches of native grasses still occur in many places on the ranch. They are dominated by purple needle grass (Nasella pulchra), but perennial species of barley (Hordeum), bluegrass (Poa spp.), three-awn (Aristida ssp.), melic (Melica ssp.), and wildrye (Elymus and Leymus ssp.) are sometimes dominant or codominant (Bainbridge and Kan, 1997). The native grasses are most abundant on mesic north-facing slopes, in the understory of mixed evergreen woodland (Arroyo Hondo), under trees in oak savannas, and in open areas on ridge tops and slopes.
Oak Woodland
Blue and valley oak woodlands have become quite rare in California, and few are protected from grazing and the encroachment of suburban development. Oak woodland covers a large extent of BORR, much of this is composed of blue and valley oaks. Compounding the possibly bleak future for oak woodlands is the lack of recruitment of young oaks. In the Mt. Hamilton area, valley oaks seem to be suffering most from this problem. The exact mechanism or mechanisms preventing oak regeneration is not known, but protection from pigs, cattle, and ground squirrels has been shown to increase survivorship of existing seedlings. Prescribed fire may also help by opening canopies and reducing competition between grasses and seedlings. However, fires must be carefully controlled for low heat, and conducted at frequency intervals that allow seedlings to become established. Physiological research suggests that ozone may extend stomata opening in blue oak, forcing nighttime transpiration during periods of drought and influencing shorter leaf retention. Oaks, as the most widespread and representative forest and woodland species in California, offer excellent research opportunities for climate change and pollution-effects research.
Non-native Plant Infestations
Among introduced species, yellow starthistle (Centauria solstitialis) and medusahead grass (Taeniatherum caput-medusae) are highly invasive. At present, C. solstitialis occupies only about 30 acres of the ranch, but it is spreading quickly. Taeniatherum, probably introduced from bales of hay, covers most of the flat areas of the ranch.
Other introduced species of concern are Italian thistle (Carduus pycnocephalus), tocalote (Centauria melitensis), Canada thistle (Cirsium arvense), and bull thistle (Cirsium vulgare). Italian thistle in particular has become widespread in dense stands, and is a spring and summer feature under the drip lines of many oaks on the ranch.
West Pond
Perennial: drained and dredged in October, 2003 to eradicate sunfish, mosquito fish, and bullfrogs. Bullfrogs re-invaded from neighboring ranches.
Approximate depth: 14 feet.
Breeding amphibians include western toad, pacific chorus frog, and California tiger salamander (self-established after pond was drained and dredged), and bullfrogs.
Contains a goose nesting platform in the SW corner, and a floating turtle raft was placed in the middle in 2007.
South Pond
Seasonal, normally dry by June. California tiger salamanders, pacific tree frogs, western toads.
Big Lake
Perennial. Drained and dredged in 2004 to eradicate largemouth bass, sunfish, Mississippi silversides, mosquitofish, and bullfrogs. Bullfrogs re-colonized from a neighboring ranch.
Breeding amphibians: California tiger salamanders (difficult to detect), western toad, Pacific chorus frog, bullfrog.
Breeding reptiles: Western pond turtle.
Breeding birds: Pied-billed grebe, Canada goose, American coot, wood duck.
Surface area=1.32 hectares (3.1 acres).
Maximum depth =29 feet.
Pumpkin Pond
Seasonal: fills with winter rains and dries by July/August.
Breeding amphibians: California tiger salamander, and pacific chorus frog.
Dimensions: Approximately 25 feet in diameter and 5 feet deep.
High Pond
Seasonal. Fills with winter rains and dries by end of May, one of the shortest hydro periods we have.
Breeding amphibians: Pacific chorus frog and California tiger salamander.
Turtle raft in the middle.
Dimensions: Approximately 20 feet in diameter and 30 inches deep.
This is the highest elevation pond at approximately 2800 feet.
Rope Swing Pond
Perennial. Drained and dredged in 2003 to eradicate sunfish, largemouth bass, and mosquitofish.
Breeding amphibians: Pacific chorus frog, and probably California tiger salamanders, though they are difficult to detect in the deep waters of this pond.
Western Pond turtles are present, but breeding status unknown.
Dimensions: Approximately 40 feet wide at dam and about 120 feet long. Depth approximately 16 feet. The pond basin is a deep wedge shape with steep sides.
Windmill Pond
Seasonal, fills with winter rains and normally dries by June. Size and shape heavily influenced by pig wallowing.
Dimensions: approximately 6 feet wide, 15 feet long, and four feet deep.
Breeding amphibians include California tiger salamanders and pacific chorus frogs. Recent sitings of Red-legged Frog, but breeding has not been confirmed.
North Pond
Seasonal: fills with winter rain and dries by June/July. Substrate frequently rooted by wild pigs. Turtle raft located in the middle.
Breeding amphibians: California tiger salamander and pacific chorus frog.
Dimensions: Approximately 35 feet in diameter, and 3 feet deep.
Gramps’ Pond
Perennial except for the driest years.
Breeding amphibians: California tiger salamander, Pacific chorus frog, California newt.
Breeding reptiles: western pond turtle. Raft present.
Cabin Pond
Perennial. Drained and dredged in 2003 to eradicate sunfish, largemouth bass, mosquitofish, and bullfrogs.
Breeding amphibians: California tiger salamander (established after pond was drained), Pacific chorus frog, Western toad, California red-legged frog. Juvenile red-legged frogs appeared in the fall of 2007, 3 years after all fish were removed from ponds on the reserve.
Breeding reptiles: western Pond turtle; turtle raft present.
Dimensions: Approximately 100 feet long, 50 feet wide, and 20 feet deep.
Dimensions: Approximately 30 feet in diameter and 6 feet deep.
Barn Pond
Seasonal. Fills with winter rains and dries by August.
Breeding amphibians: California tiger salamander, Pacific chorus frog.
Dimensions: Approximately 12 feet in diameter and 3 feet deep.
Lower Turtle Pond
Seasonal. Fills with winter rains and dries by August.
Breeding amphibians: California tiger salamander, Pacific chorus frog.
Breeding birds: wood duck.
Dimensions: 15 feet wide, 60 feet long, and 14 feet deep.
The productivity in this pond comes mostly from allochthanous materials, since it is tucked deep in a ravine under oak trees. There is very little emergent or littoral vegetation.
Upper Turtle Pond
Perennial. Drained and dredged in 1992, prior to stewardship, in order to repair a leaking dam.
Breeding amphibians: California tiger salamander, Pacific chorus frog.
Breeding reptiles: Western pond turtle. New turtle raft placed in 2007.
Breeding birds: Red-winged blackbird.
Dimensions: Approximately 50 feet in diameter and 10 feet deep.
Contractor reportedly captured California newts and transferred them to Big Lake. They were never detected there in subsequent surveys and were likely eaten by largemouth bass. They never re-colonized this pond.