Natural History of the Central Coast Bioregion
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ANR Publication 8597 | July 2019 https://doi.org/10.3733/ucanr.8597 http://anrcatalog.ucanr.edu WILLIAM D. TIETJE ENVIRONMENTAL SCIENCE, Policy, and Management, University of California, Berkeley WILLIAM L. PRESTON GEOGRAPHER EMERITUS, California Polytechnic State University, San Luis Obispo ANNE Y. POLYAKOV ENVIRONMENTAL SCIENCE, Policy, and Management, University of California, Berkeley Central Coast oak woodland landscape. Photo: Bruce Lyon Natural History of the Central Coast Bioregion hether one drives the Big Sur on the west by the Pacific Ocean W coastline, or stands at the foot and on the east by the San Joaquin of a giant coast redwood (Sequoia Valley, Carrizo Plains, and the sempervirens) or in the shade of interior Transverse Ranges. Across an ancient valley oak (Quercus the bioregion’s 15,000 square miles It is advisable to lobata), it is clear that California’s (9% of California’s area), physical look from the tide Central Coast Bioregion embodies and biological processes, combined pool to the stars exceptional biological diversity and with time and human actions, and then back to natural beauty. Extending from the have resulted in a broad range of the tide pool again. southwest corner of San Joaquin ecosystems, each harboring distinct — John Steinbeck, County south to northern Ventura assemblages of plants and animals. from The Log from the Sea of Cortez County, the bioregion is bounded ANR Publication 8597 | Natural History of the Central Coast Bioregion | July 2019 | 2 Similar to most California regions, the working landscapes dominated by livestock current human inhabitants of the Central grazing and farming, with interspersed Coast Bioregion are concentrated in urban areas devoted to open space conservation areas. However, much of the rural environs are and nature-based recreation. Examples of natural attractions include iconic oak- studded rangelands, Monterey Bay, and the rugged splendor of the Big Sur coastline. The biodiversity of these fascinating environments is threatened by exurban development, agricultural expansion, and increasingly by climate change. The conservation challenges are formidable, but creative measures are being developed and implemented to sustain both biodiversity and the livelihoods of the bioregion’s residents. PHYSICAL ATTRIBUTES Geology The Central Coast Bioregion lies mainly within the Southern Coast Ranges, with its southernmost extent encompassing the western Rocky shoreline at Big Sur. Photo: Bruce Lyon portion of the Transverse Ranges. Most of N e C va a l d the region is comprised of rolling and hilly ifo a rn ia topography with scattered areas exhibiting very steep slopes. Average elevations are generally S below 3,000 feet. However, more prominent ie r r highlands are found in the Transverse Ranges, a N which contain over three dozen summits that e v D a surpass 6,000 feet in elevation. One of these ia d b a l is Mount Pinos at 8,831 feet. It is the tallest S o a n R Elkhorn a mountain in the bioregion. Impressive uplands !( B n e Slough n g Salinas i e t o are also encountered in the Santa Lucia, Monterey R S i v Sa S e a Caliente, San Rafael, and Diablo mountains. a r n n l i t n Jo a a Of these, the loftiest are in the Santa Lucia ¤£1 L s u a ci R q Mountains, which rise abruptly from the Big a iv u R e in a r Sur coast to elevations exceeding 5,000 feet. n £5 V g ¤ a e l Monterey Bay le The bioregion’s surface landforms are y ¤£101 National Marine S primarily sedimentary in content with a 46 Sanctuary n ¤£ San Luis A varying intermixtures of metamorphic and n Obispo Si d Morro e r igneous rock materials. With the exception r e Bay ra a M s of the Transverse Ranges, the mountains and Santa a F d a intervening valleys trend in a northwest- Maria re u l t to-southeast direction. The Southern Coast Tran sver Ranges are geographically divided into three S se R a n t a ang Y n e es z R. linear belts that roughly align with the overall structural orientation. Each is distinguished ± Santa Barbara according to surface rock content and Santa Barb 0 40 80 ara Channel delineating fault lines. In the northern portion Miles of the bioregion, lying between the San Physical geography of the Central Coast Bioregion. Joaquin Valley and the San Andreas Fault, Source: R. Johnson, UC ANR IGIS Program is the eastern belt. It is largely composed of ANR Publication 8597 | Natural History of the Central Coast Bioregion | July 2019 | 3 a geological formation called the Franciscan plant communities. With sufficient moisture, Assemblage. Folded metamorphic (e.g., schist the majority of the soils in the drier interior and serpentine) and sedimentary rocks (e.g., are adequate to support grasslands, shrublands, sandstones and shales with some limestone) and woodlands. An exception to this pattern are the principal components. To the west of is found on higher ridges, where slopes are the San Andreas Fault is the central belt, or steeper. These environs tend to have shallow the Salinan Block. This formation possesses soils and are more conducive to supporting a core of granitic and metamorphic materials grass and shrub communities. Closer to the that are overlaid by younger sediments. The coast where rainfall is higher, soils are typically Sur-Nacimiento Fault defines the belt’s western deeper and nurture a striking mosaic of edge, and between it and the coast is found grassland, chaparral, woodland, and riparian the Nacimiento Block. Here Franciscan crustal communities. materials are once again foremost; however, In contrast to the soils on hilly land, stream they contain more surface igneous (i.e., floodplains and deltaic plains are largely volcanic) features than the interior regions. composed of depositional or alluvial soils. The western extension of the Transverse These materials are usually deeper and more Ranges constitutes the southern reaches of fertile than those found on adjacent uplands the bioregion, and their structural orientation and are well represented in the floodplains contrasts with the Southern Coast Ranges. That and deltas of the Salinas, Santa Maria, and is, they have more of an east to west alignment Santa Ynez rivers. Not surprisingly, they are than the highlands to the north. Although used extensively for orchards, vegetable crops, the Santa Ynez Fault separates the Transverse vineyards, and grazing. Ranges from the Southern Coast Ranges, both These comprehensive soil patterns are share some geologic properties. For example, punctuated in places by parent materials Salinan Block and Franciscan rock materials exhibiting chemistries that produce unique are well represented in the western Transverse soil and vegetation communities. Perhaps Ranges. Serpentine soils most renowned in this respect are serpentine soils, which are more abundant in the produce unique Soils plant assemblages. western areas of the bioregion. They contain Soils of the bioregion are mainly residual, Predominant plants large concentrations of heavy metals and having formed in place through the shown here are a deficiency of the more common plant goldfields and purple decomposition of underlying rock material. nutrients. Consequently, areas with serpentine needlegrass, a perennial Soil depth (measured to bedrock) varies and soils are easily distinguished from adjacent native bunchgrass that is a factor that strongly influences associated thrives on serpentine communities by plants that have managed to soils. Photo: Matt Ritter adapt to these unusual soils, such as San Luis Obispo sedge (Carex obispoensis), serpentine manzanita (Arctostaphylos obispoensis), leather oak (Quercus durata), and Sargent cypress (Hesperocyparis sargentii). Climate The climate of the Central Coast Bioregion is quintessentially Mediterranean. It is characterized by cool, rainy winters with occasional snowfall on the higher peaks and warm to cool rainless summers. In addition to this general climatic pattern, the region experiences periodic El Niño–La Niña cycles that alternate between wetter than average and drier than average conditions. ANR Publication 8597 | Natural History of the Central Coast Bioregion | July 2019 | 4 Moisture-bearing storms originate offshore Over the course of a winter, temperatures of and bring precipitation that varies according 32°F and below occur on occasion and happen to topography, latitude, and distance from with a greater frequency inland from the coast. the coast. Average annual precipitation for For the majority of the bioregion, the first day the entire bioregion hovers around 20 inches, of freezing temperatures normally takes place with coastal highlands receiving significantly during the last week of November or later. In more. For instance, in the north near Monterey, turn, the last day for frost typically occurs in yearly precipitation at the higher elevations late February and early March. The outcome is in the Santa Lucia Mountains can surpass 50 a frost-free growing season of approximately inches. 250 days. The exceptions are along and directly Average annual precipitation also typically inland from the Big Sur coastline and at higher declines from west to east. This pattern is elevations in the Transverse Ranges, where the strongly influenced by elevational differences growing season is 3 to 4 weeks shorter. It has within the Transverse and Southern Coast increased by over 15 days during the last 100 ranges. In essence, the western, or windward, years due to climate change, and this trend is sides of highlands receive more precipitation expected to continue. than the downwind, or lee, slopes and Hydrology lowlands. This topographic and moisture The location, size, and hydrology of the pattern repeats itself across the bioregion. bioregion’s major watersheds are determined A west-to-east transect along the boundary mainly by precipitation and topography. between Monterey and San Luis Obispo Perennial and intermittent streams, along with counties is a case in point.