LANDFIRE Biophysical Setting Model Biophysical Setting 0410920 Southern California Coastal Scrub

LANDFIRE Biophysical Setting Model Biophysical Setting 0410920 Southern California Coastal Scrub This BPS is lumped with: This BPS is split into multiple models: General Information Contributors (also see the Comments field) Date 3/21/2006 Modeler 1 Robert Taylor [email protected] Reviewer Jan Beyers [email protected] Modeler 2 Reviewer Jon Keeley [email protected] Modeler 3 Reviewer Richard Minnich [email protected] u Vegetation Type Dominant Species Map Zone Model Zone ARCA11 Upland 4 Alaska Northern Plains ERFA2 Savannah/Shrub California N-Cent.Rockies Steppe General Model Sources SAME3 Great Basin Pacific Northwest Literature SALE3 Great Lakes South Central Local Data SAAP2 Hawaii Southeast Expert Estimate MALA6 Northeast S. Appalachians RHIN2 Southwest ENCA Geographic Range California Southern Coast Ranges, which includes: Section 261A-Central California Coast, and Section 261B-Southern California coast (Mcnab and Avers 1994). This system is found in more or less continuous bands near the coast from approximately San Benito County, California, south into northern Baja California, Mexico. It occurs below 1000m (3000ft) elevation. Coastal scrub communities extend further inland in areas where the marine climatic influence extends further inland due to gaps in coastal mountain ranges, as in western Riverside County, and in the Salinas Valley, the Santa Clara River, Santa Margarita River, and many other coastal river valleys. In the Santa Monica Mountains (Ventura and Los Angeles Counties), the Santa Ana Mountains (Orange County), and other parts of the coast range, coastal scrub occupies a low to mid elevation band on both the coastal and the interior side of many coastal mountains, transitioning to chaparral communities at higher elevations. A reviewer noted that maps of the distribution of southern coastal scrub is given in Minnich and Franco (1998). Biophysical Site Description The most important environmental factors are cool season precipitation and minimum winter temperature. Mean minimum winter temperature is substantially more predictive of southern sage scrub distribution patterns than is mean maximum summer temperature. Southern scrub prefers warm winters and relatively low total precipitation. This means that it is restricted to low elevation areas that receive some marine climatic influence. Southern coastal scrub often responds sensitively to aspect on a local **Fire Regime Groups are: I: 0-35 year frequency, surface severity; II: 0-35 year frequency, replacement severity; III: 35-100+ year frequency, mixed severity; IV: 35-100+ year frequency, replacement severity; V: 200+ year frequency, replacement severity. Thursday, January 23, 2014 Page 1 of 11 scale (for example, in San Diego County sometimes occurring on south-facing slopes where north-facing slopes are occupied by chaparral types), but occurs on all aspects when viewed at a regional scale. Species composition of stands varies both with distance from the coast, and with latitude. It occurs below 1000m (3000ft) elevation and about 10-60cm of annual precipitation. Soils vary from coarse gravels to clays but typically only support plant-available moisture with winter and spring rain. Stands often form complex mosaics interdigitated with stands of chaparral and grassland types on scales of 10s-100s of meters. Vegetation Description Southern coastal scrub is a diverse plant community of summer deciduous and evergreen shrubs frequently dominated by Artemisia californica, Eriogonum fasciculatum, and species of Salvia. Its distribution extends from near San Francisco in central California to just south of El Rosario, northern Baja California, Mexico, where it is perhaps better called succulent sage scrub (Mooney 1972; Mooney 1977). Characteristic plant species include Artemisia californica, Salvia mellifera, Salvia apiana, Salvia leucophylla, Encelia californica, Eriogonum fasciculatum, Eriogonum cinereum, Opuntia littoralis, Mimulus aurantiacus, Malosma laurina, Rhus integrifolia, Lotus scoparius, Rhamnus crocea, and Baccharis pilularis. Coastal sage scrub is distinguished from chaparral physiognomically and floristically. Most dominant species of coastal sage scrub are aromatic, soft leaved (malacophyllous), facultatively dimorphic or drought deciduous, woody or half-woody, shallow-rooted shrubs and subshrubs. They contrast with the leathery leaved (sclerophyllous), evergreen woody shrubs of the adjacent chaparral. A few sclerophyllous species (Malosma laurina, Rhus integrifolia, Heteromeles arbutifolia) are typical of southern coastal scrub. Where these species occur, they are generally emergents from two to four meters high, in a matrix of one to 1.5m high malacophyllous shrubs and subshrubs. Southern coastal scrub is typically comprised of a shrub layer dominated by one to several species in any given stand with a considerably more diverse understory of herbs and grasses (Mooney 1977; Westman 1981). This type has moderate alpha diversity, and rather greater beta and gamma diversity, since there are a number of sub-types of this plant community. Moving from mesic to xeric sites (as along a latitudinal gradient, or as distance from the coast increases), dominance generally shifts from evergreen species in the north to drought-deciduous species. The number of succulent species increases as one moves south, and in southern San Diego County the type has accumulated enough of these to warrant classification as Baja Semi-Desert Coastal Succulent Scrub. Variation in coastal influence at a given latitude also produces composition changes. Coastal Rhus integrifolia gives way to interior Rhus ovata. Dominant species typical of interior sites include Salvia apiana, and Eriogonum fasciculatum. At the eastern edge of this community’s southern distribution, the type transitions into desert scrub types. Encelia californica occurs only very near the coast, but Encelia farinosa appears on the eastern edge of the southern distribution. Eriogonum fasciculatum and Yucca schidigera continue east into desert types, but southern coastal scrub is generally considered to end where Artemisia californica is replaced by Artemisia tridentata. Across this broad geographic range, associated species vary widely. Types recognized in publications include a Salvia leucophylla-dominated northern types (Westman and Axelrod’s Venturan associations), a southern Salvia mellifera-dominated type, and types dominated by Artemisia californica, Eriogonum fasciculatum, Rhus integrifolia, and Encelia californica. A coastal (Diegan) type and and an interior (Riversidian) type have been described by several authors. Eriogonum cinereum, dominant in northern coastal types as far south as the Santa Monica Mountains, gives way to the more xeric-adapted Eriogonum fasciculatum south and inland of there. **Fire Regime Groups are: I: 0-35 year frequency, surface severity; II: 0-35 year frequency, replacement severity; III: 35-100+ year frequency, mixed severity; IV: 35-100+ year frequency, replacement severity; V: 200+ year frequency, replacement severity. Thursday, January 23, 2014 Page 2 of 11 Disturbance Description Fires and other disturbances in this group can be characterized as follows: variable frequency (times between fires), season and intensity, depending on the size of and proximity to Native American village sites. The largest and most intense fires in modern times occur overwhelmingly during fall Santa Ana wind events between late September and early December. This was almost certainly also the case in prehistoric times. There was disagreement between the modeler and one reviewer about the role that Santa Ana winds play in the fire dynamics of this type. The reviewer indicated that the dominance of Santa Ana wind-driven fires is an artifact of fire suppression. Most free-running fires in this assemblage in Baja California occur in summer (Minnich 1983). The Mensing (1998) study cannot constrain Santa Ana winds from summer “sundowner” winds, i.e, north winds in Santa Barbara in June-August occur simultaneously with onshore westerly winds elsewhere in California and northern Baja California. Most burning in coastal sage scrub in Baja California occurs in summer when there are no Santa Ana winds. The modeler disagreed stating that modern Santa Ana wind-driven wildfires burn through all vegetation types and ages, exhibiting extreme fire behavior and spotting across all manner of fire defenses. The fuel-driven hypothesis may be adequate in moderate weather where fire behavior is actually fuel-driven, but 90+% of the acres burn in weather-driven fire events where all manner of fuels burn with extreme fire behavior. Even if a lot more acres burned under moderate weather conditions north of the Mexican border, the fall Santa Anas would still whip big fires across shrublands of all ages, as they do today. There might be more type conversion from shrublands to ruderal grasslands with the shorter inter-fire intervals this scenario would produce. Furthermore the modeler indicated that he was not yet convinced that the Santa Ana wind patterns are equal north and south of the Mexican border. A paucity of good weather data for Baja CA may make this comparison a difficult one, but it remains to be demonstrated. Another reviewer offered comments on the debate outlined in the previous paragraph. This reviewer felt that from a vegetation management point of view (that is, leaving the public safety aspects to others) this debate about when the most fires occurred in 1700 is somewhat beside the point.

Load more