Jasper Ridge Biological Preserve
Map SatelliteOne of the oldest academic preserves in the country, Jasper Ridge offers unusual diversity of plant communities, as detailed below, plus a recorded natural history beginning in 1891 that includes more than 100 advanced degrees and numerous research publications.
Grasslands occupy 140 hectares (350 acres), of which 40 hectares (100 acres) are on serpentine soils supporting such native perennials as squirreltail, Elymus multisetus, oat grass, Danthonia californica, spear-grass, Stipa lepida, and purple needlegrass, Nassella pulchra, as well as serpentine endemics and an impressive array of wildflowers. Sharp boundaries separate the serpentine from surrounding greenstone/sandstone soils which support another 40 hectares of grassland dominated by exotic annuals. This 80-hectare (200-acre) ridgetop combination has been ungrazed since 1960 and is largely undisturbed. Along the base of the ridge are a separate, more disturbed 60 hectares (150 acres) of annual grasslands, half of which are still grazed.
A 60-hectara (150-acre) woodland/savannah of blue oak, Quercus douglasii, and mixed grasses adjoins the upper grassland, and a small mixed oak woodland has survived below. Chaparral occupies 100 hectares (250 acres) on southwest slopes and a few crest areas on serpentine soils. Chamise, Adenostoma fasciculatum, is the dominant plant, with the usual range of associates. Leather oak, Quercus durata, occurs on the serpentine.
A mixed evergreen forest of 100 hectares (250 acres) covers the northern and eastern hillsides. It includes| several stands of second-growth redwood, Sequoia sempervirens, and some Douglas fir, Pseudotsuga menziesii. A system of intermittent streams, the upper portion of which was impounded in 1892 by a 20-meter (67-foot) dam, produced 120 hectares (300 acres) of related plant communities. By 1930 primary headwaters of the lake had silted in to form a 30-hectare (75-acre) swamp, with crown cover of red willow, Salix laevigata, and white alder, Alnus rhombifolia. Silting of secondary headwaters formed a 30-hectare marsh of cattail, Typha latifolia, and swamp knotweed, Polygonum amphibium var. emersum. About 30 hectares of open lake still remain. Downstream there are about 30 hectares of riparian growth along 3 kilometers (2 miles) of preserved natural streambed carrying dam overflow plus water from a major tributary.
Over 130 species of birds and 25 species of mammals have been recorded in the Preserve, including resident coyote, Canis latrans, and bobcat, Lynx rufus. An intensive 18-year study still continues of the checkerspot butterfly, Euphydryas editha, three distinct populations of which are confined to the serpentine, and its close relative Euphydryas chalcedona in the chaparral.
Geologically complex, Jasper Ridge is underlaid by Franciscan greenstone, chert, serpentine, and a little graywacke; by an Eocene sandstone, and by Santa Clara sandstone and conglomerates. The area overlaps the San Andreas Fault and has many faults and contacts.
Integrity: Cattle grazing took place from ca. 1833 to 1960 on the ridgetop and continues today at the base. Redwoods were logged ca. 1850. Sporadic mining took place from ca. 1875 to 1913. Lower grasslands have been manipulated in various ways. There have been no major fires, at least in the 20th century.
Use: Research, educational, observational.
Ref: Ray, K., et al, 1972. A Guide to Jasper Ridge. Mimeo. 52 pp.
November 1979
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman
