Natural Resources
Conservation Service
ecological site group R004BN201CA
Windy coastal perennial grassland terraces and bluffs
Accessed: 09/14/2026
Ecological site group description
Key Characteristics
- Santa Cruz Mountains – LRU N
- Soils supporting rangelands
Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
Physiography
This ecological site is generally found on open ridgetops, flatter, south-facing exposures.
Climate
The average annual precipitation in this MLRA is 23 to 98 inches (585 to 2,490 millimeters), increasing with elevation inland. Most of the rainfall occurs as low-intensity, Pacific frontal storms. Precipitation is evenly distributed throughout fall, winter, and spring, but summers are dry. Snowfall is rare along the coast, but snow accumulates at the higher elevations directly inland. Fog is a significant variable that defines this MLRA from other similar MLRAs. Summer fog frequency values of greater than 35% are strongly correlated to the extent of coast redwood distribution, which is a primary indicator species in this MLRA. Nighttime fog is approximately twice as common as daytime fog and seasonally, it reaches its peak frequency in early August, with the greatest occurrence of fog from June through September (Johnstone and Dawson 2010). The average annual temperature is 49 to 59 degrees F (10 to 15 degrees C). The freeze-free period averages 300 days and ranges from 230 to 365 days, decreasing inland as elevation increases.
Climate varies from the west to the east in LRU N, the Santa Cruz Mountains, as the high mountain ridges reduce the penetration of maritime air. Winters are cool and wet with the occasional snowstorms at the highest elevations and in narrow, north-facing drainages, leading to some white and red fir in limited locations. Heavy rains are also known to cause mudslides throughout this LRU, and on the west side, summers are cooler, and fog or low overcast skies are only around for the mornings and carry through the low slopes and stream terraces.
Soil features
Although the soils of this provisional site concept are highly varied, they are generally shallow to a restrictive horizon or skeletal, creating difficult growing conditions for trees and shrubs. This LRU receives far less summer fog and therefore these types of soils that are shallow or skeletal become dry during crucial summer growing days and provide conditions primarily suitable to grasses, forbs and some competitive scrub species.
Vegetation dynamics
This provisional ecological site concept attempts to describe the coastal prairies and coastal scrub shrublands of this LRU. They exist in a patchwork of herbaceous to dense woody shrub cover wherever the cooling influence of the Pacific Ocean moderates the summer drought (high evapotranspiration rates). This concept lumps many of the unique scrub and prairie expressions into one large concept, due to limited soil mapping that successfully parses out the differences between these types and focuses primarily on the primary abiotic factors and ecological dynamics that maintain and/or alter these vegetative communities. This provisional ecological site concept covers a wide variety of coastal scrub and prairie dynamics and expressions that will need to be further refined to better represent dynamics on a smaller, more ecologically specific scale.
Abiotic Factors
The primary factor that maintains these sites in either coastal scrub or coastal prairie are the shallow to restrictive layer soils that dry out easily and do not hold much soil moisture into the summers, steeper more unstable slopes, and exposed locations on the landforms that create harsher growing conditions for trees and many shrubs. Coastal scrub and herbaceous species are more readily able to colonize and stabilize and adapt to these conditions, which explains why they dominate these open areas and trees do not.
Primary Disturbances
The primary disturbances to this ecological site concept are the harsh soils that create difficult growing conditions, grazing, and fire. Historically, lightning-ignited fires are thought to have occurred in the surrounding forested habitats and would have burned significant acres across many soil types and landforms. Between soil and landform differences and frequencies and intensities of burning that would be interacting with yearly weather patterns that shifted between wet years to drier years, this would have created a patchwork of areas that returned over time to forest while others remained in coastal scrub and grassland. It is also believed that native grazers were common in these lower gradient coastal plains and may have contributed to the open nature and complex patchwork of coastal scrub and prairies. In combination with the fires and periodic droughts, grazers may have assisted in maintaining areas with good soils in more herbaceous vegetation and the less ideal soils in a more coastal scrub and grass patchwork expression. Native American use along these coastlines would also have included burning to maintain as much of the coastal prairies as possible, often times quite frequently to improve hunting and grass and forb production for plant harvesting.
Historically, this ecological site would likely have been much more extensively covered by the coastal prairies due to the repeated burnings by many of the coastal tribes and the scrub species would have likely been more confined to the more inaccessible areas of the site. As the fires became less and less frequent, the coastal scrub species was able to encroach back into the grasslands. Areas where grazing still occurs either by livestock or native grazers, tend to maintain a more open grassland, however they have become a mix of native perennials and forbs and annual grasses and forbs since the introduction of the non-native seed sources and heavy pressures from grazing. Fire to this ecological site is less likely now, due to the urban development and cultivation of much of these areas along the coast however if it does occur, the severity of the fire may be much higher due to the amount of fuels that have built up since the last fire.
Major Land Resource Area
MLRA 004B
Coastal Redwood Belt
Stage
Provisional
Contributors
Kendra Moseley
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