California Coastal Sand Chaparral

This ecological system includes chaparral in patches restricted by edaphic conditions (sands, sandstones, other marine sediments, and stabilized sand dunes) within the fog belt throughout the central and northern California coast. This system is characterized by a combination of locally endemic species of Arctostaphylos and Ceanothus, species that primarily reproduce by seed rather than resprouting. Shrubs vary in height (up to 3 m tall) and occur in variable densities. More open patches support herbaceous vegetation, while occurrences of high shrub density have no understory. Characteristic species include Arctostaphylos tomentosa, Arctostaphylos nummularia, Arctostaphylos tomentosa ssp. crustacea, Arctostaphylos hookeri, Arctostaphylos pajaroensis, Arctostaphylos montaraensis (and others), Ceanothus masonii, Ceanothus griseus, and Ceanothus verrucosus. In occurrences in southern Oregon, Arctostaphylos hispidula is the predominant chaparral shrub. Southernmost stands (San Diego County) can include Cneoridium dumosum and Comarostaphylis diversifolia. Other common widespread woody taxa can include Adenostoma fasciculatum, Eriogonum fasciculatum, Salvia mellifera, Frangula californica, Rhamnus crocea, and Quercus agrifolia. Controlled burns have resulted in poor survivorship of the Arctostaphylos spp., and current theories are that they need long fire-free intervals to develop a viable seedbank that can reproduce following fire. This system often co-occurs with California Coastal Closed-Cone Conifer Forest and Woodland (CES206.922).

This system is characterized by a combination of locally endemic species of Arctostaphylos and Ceanothus, species that primarily reproduce by seed rather than resprouting. Shrubs vary in height (up to 3 m tall) and occur in variable densities. More open patches support herbaceous vegetation, while occurrences of high shrub density have no understory. Characteristic species include Arctostaphylos tomentosa, Arctostaphylos nummularia (= Arctostaphylos sensitiva), Arctostaphylos tomentosa ssp. crustacea (= Arctostaphylos crustacea), Arctostaphylos hookeri, Arctostaphylos pajaroensis, Arctostaphylos montaraensis (and others), Ceanothus masonii, Ceanothus griseus, and Ceanothus verrucosus. In occurrences in southern Oregon, Arctostaphylos hispidula is the predominant chaparral shrub. Southernmost stands (San Diego County) can include Cneoridium dumosum and Comarostaphylis diversifolia. Other common widespread woody taxa can include Adenostoma fasciculatum, Eriogonum fasciculatum, Salvia mellifera, Frangula californica (= Rhamnus californica), Rhamnus crocea, and Quercus agrifolia.

This system is restricted by edaphic conditions (sands, sandstones, other marine sediments, and stabilized sand dunes) within the summer coastal fog belt throughout the central and northern California coast, usually below 300 m (1000 feet) in elevation (Keeley and Davis 2007, Sawyer et al. 2009). The climate is distinctly Mediterranean, with warm, dry summers and cool, moist winters. Rainfall is rather variable due to the large latitudinal range. Sandy soils with low nutrient levels tend to be the norm, usually within just a few kilometers of the ocean.

These shrublands are characterized by species that primarily reproduce by seed rather than resprouting, and are fire-dependent. Infrequent fire results in encroachment of trees and a decline in shrub vigor and seedbank quality. Frequent fire tends to convert the stands to coastal scrub or grassland. Recent studies of many sites that have been fire-free for decades suggest that at least some of the species of Ceanothus may be able to germinate without fire and thus sustain populations for long fire-free intervals. Controlled burns have resulted in poor survivorship of the Arctostaphylos spp., and current theories are that they need long fire-free intervals to develop a viable seedbank that can reproduce following fire (Keeley and Davis 2007). Most of the dominant shrubs are nitrogen fixers.

Landfire (2007a) model: Chaparral burns in high-intensity, stand-replacing crown fires that burn large acreages in a single event. However, there is a considerable range in the flammability of shrub species (e.g., chamise is "flashier" than manzanita). Large, stand-replacement events can interact with seed availability and, hence, influence post-fire successional pathways differently than for smaller, less severe fires. Mean fire-return intervals are variable and longer than intervals of other chaparral types. Fire intervals can exceed 100 years, and the specimens can grow to large size. Season of burning plays a large part in species composition. Occasionally, frost affects mortality and increases fuel buildup.

Conversion of this type has commonly come from coastal residential development and urbanization, military operations, and fire suppression which eliminates stands (Griffin 1978, Davis and Borchert 2006). Common stressors and threats include fragmentation of the habitat by housing, and agriculture may make utilization of prescribed fire impossible (Van Dyke et al. 2001). Exotic, invasive weeds, including Cortaderia jubata, Carpobrotus edulis, Carpobrotus chilensis, Genista monspessulana, and Eucalyptus globulus (a tree), also threaten some occurrences where these species are invading nearby vegetation (Griffin 1978, Van Dyke et al. 2001). It was speculated by Davis and Borchert (2006) that this type is more densely invaded by exotics than other chaparrals because it is more densely roaded and thus closer to human disturbance and sources of exotic propagules.

In the west central coast region of California, regional climate models project mean annual temperature increases of 1.6-1.9°C by 2070. The projected impacts will be warmer winter temperatures, earlier warming in spring and increased summer temperatures. Regional models project a decrease in mean annual rainfall of 61-188 mm by 2070. While there is greater uncertainty about the precipitation projections than for temperature, some projections call for a slightly drier future climate relative to current conditions (PRBO Conservation Science 2011).

In many coastal regions, the interaction between oceanographic and terrestrial air masses may be ecologically important. Intensifying upwelling along the California coast under climate change may intensify fog development and onshore flows in summer months, leading to decreased temperatures and increased moisture flux over land (Snyder et al. 2003, Lebassi et al. 2009, as cited in PRBO Conservation Science 2011). Coastal terrestrial ecosystems could benefit from these changes. However, current trends in fog frequency along the Pacific coast from 1901-2008 have been negative (Johnstone and Dawson 2010, as cited in PRBO Conservation Science 2011), thus the effect of climate change on coastal fog remains uncertain. Potential climate change effects could include (PRBO Conservation Science 2011): deep-rooted or phreatophytic species under greater stress and death; drop in groundwater table; more and larger fires; increased fire frequency due to warmer temperatures resulting in drier fuels; increased invasive species due to lack of competition from native species whose vigor is reduced by drought stress, and increased fire intervals favor certain invasive species (Brooks and Minnich 2006); increases in the areal extent of grasslands and concomitant reductions in the extent of chaparral, sage scrub, and oak woodlands; and increased competition for water from all users, and stresses on the already overtaxed water allocation of California agricultural system (PRBO Conservation Science 2011).

This systems occurs within the fog belt from southern California to the Mendocino coast of northern California. It extends north into coastal Oregon in very small patches.