Santa Lucia Fir

The California Floristic Province is considered one of the most diverse floristic provinces in the world. This is largely due to the province being endowed with a unique Mediterranean climate, some complex geology and lots of topographic relief. Combined, these features have enriched the California landscape with edaphic and microclimatic conditions that provide a rich variety of habitat niches. And habitat niches can help drive plant speciation, especially in California.

Habitat niches also give refuge to plants that were once more widespread during a time when California's climate was much different than today. By continuing to mimic conditions of the past, these refuge niches have allowed plants with an ancient lineage to persist amidst a changing climate. They have also allowed plants from long ago to coexist alongside newly speciated plants, making the California flora what it is today.

Early in the Cenozoic Era (~ 65 MYA) the climate of western North America was warm and temperate with summer rain occurring along the coast of North America (California did not yet fully exist). During that time, palm trees grew in present day Wyoming, as is often said. 

This warm and moist climate was ideal for many conifer species, allowing them to cover a large swath of western North America. But, over time the climate changed. Around 5 million years ago the climate became substantially colder and drier. That climatic shift had a large impact on the diversity of plants growing throughout western North America. Some conifers were forced to migrate out of environments that were too cold and dry and eventually retreated to the temperate coast.

An ancient conifer specie named Abies sherii was likely one of those conifer species affected by the climatic shift. Abies sherrii no longer exists today, but fossil evidence has been found in two regions of western Nevada. During the early Cenozoic, the coastline of western North America was located somewhere near western Nevada. It's therefore assumed that Abies sherrii preferred the warm and temperate coastal environment that existed there. It's also assumed that as North America's coastline continued moving westward due to plate tectonics (and California began to take shape) that Abies sherii also continued to migrate westward. 

Based on morphological studies of Abies sherrii fossils, it's believed that Abies sherrii is the ancient genetic parent to present day Santa Lucia Fir (Abies bracteata). The Santa Lucia Fir is a rare species of fir tree that grows only within the Santa Lucia Mountains of central & southern California. Santa Lucia Fir grows in scattered groves along the outer range of the mountains, where proximity to the Pacific Ocean provides favorable growing conditions. The groves occur along the peaks, ridgelines and creek channels that have contact with a cool and moist air mass moving off the Pacific Ocean. 

Like other fir trees, Santa Lucia Firs have endured California’s drought-like summers by favoring sites that are both cool and moist. The relatively cool and moist conditions at these sites helps lower evapotranspiration rates and lessens the impacts of California’s drought-like summers. A lower evapotranspiration rate helps the plant retain water and summer fog provides supplemental moisture when rainfall is absent. That in turn allows the Santa Lucia Fir to remain relatively hydrated year round, despite the pronounced period of dry that may remain elsewhere in California. 

Finding sites in California that remain cool and moist year round can be challenging. The California Floristic Province occurs within a semi-arid climate known for long dry summers. For this reason, the Santa Lucia Firs that exist in California today hug the peaks, ridgelines and creek channels just inland from the central California coastline. 

The peaks, ridgelines and creek channels of the Big Sur coastline have preserved a microclimate that somewhat mimics the conditions that occurred during a time when Santa Lucia Fir was more widespread. Creek channels provide a consistent flow of water and are often tucked in shady ravines that remain cool and moist year round. 

Cold air occurs at higher elevations, which is why Santa Lucia Fir likes the peaks and ridgelines along the Big Sur coastline. As air rises in elevation, the air mass expands and causes a drop in air pressure. The reduced air pressure means the air holds less heat. If enough moisture is contained within a cooling air mass, condensation in the form of rain or water vapor (like fog) begins to build. The cool, moist air not only provides precipitation, but it also reduces the overall drying effect. The Big Sur coastline is known for summer fog.  

The peaks and ridgelines are also advantageous for Santa Lucia Fir because the higher elevations typically experience higher precipitation rates. Couple that with the temperate conditions of the coastal environment, and what results are sites where more moisture is retained for a longer portion of the growing season. 

Abies bracteata (Santa Lucia Fir)

Abies bracteata (Santa Lucia Fir) - Cone

Image from Wikipedia https://en.wikipedia.org/wiki/Abies_bracteata 

Image by http://www.botanicus.org/bibliography/b11764600 

Abies bracteata from Plate 5 volume 1 of "L'Illustration Horticole Journal Special des Serres et des Jardins"

While finding cool and moist microclimates are essential for the survival of Santa Lucia Fir, it's also not the only imperative. Avoidance of a regular fire interval is equally critical for Santa Lucia Firs. Their long term survival depends upon it.

Unlike other fire tolerant conifer species, Santa Lucia Fir lacks a thick layer of bark that insulates them from fire damage. As such, devastating fires have the potential to wipe out populations of Santa Lucia Firs. And fewer trees ultimately lead to declining reproduction rates, which is obviously not good for their long term survival.

To evade the impacts of fire, Santa Lucia Fir also selects sites where fire is relatively infrequent. They often select north facing exposures of precipitous terrain where the temperatures are definitely more cool and moist. Those sites also lack any buildup of leaf litter (or needle duff) and are primarily composed of rocky mineral soils. So when fire does pass through, it burns with less severity. The absence of leaf litter is important because leaf litter can often cause a ground level fire to build in height and become a more devastating crown or canopy fire. Canopy fires are often very destructive with more devastating long term impacts. Canopy fires also have the potential to produce extreme heat that affects the viability of the seed bank within the soil. A devastating fire event could exacerbate a specie's recovery by greatly diminishing their generational succession.

Many paleoendemic plant species, like Santa Lucia Fir, adjusted to these kinds of threats by migrating to habitat niches where such threats are greatly reduced. They select habitat niches that preserve growing conditions mimicking their historical environs. In a sense, these kinds of habitat niches are like a window into a past time when the specie was more numerous and widespread. Cone Peak provides such a window.

Young Santa Lucia Fir seedling growing in the granite scree of Cone Peak's north slope

Afternoon shade in Santa Lucia Fir habitat, Cone Peak.

Within a distance just under 6 miles, Cone Peak rises from sea level to just over 5,000’ in elevation. It’s one of the steepest gradients in the Unites States. It’s proximity to the coast makes for a cool, moist and temperate environment and makes it home to one of the larger stands of Santa Lucia Firs.

As the contemporary climate continues to warm and become increasingly arid, concern remains for the Santa Lucia Fir. A drier climate increases the likelihood that fire behavior may change. A hotter climate means temperatures at higher elevations will warm as well. Added environmental stress may also weaken the species' ability to withstand disease and pest infestations. It is literally an uphill battle. 

(Just following the time of this writing, the Dolan Fire of 2020 burned through the Cone Peak area. The Dolan Fire was part of California's 2020 fire siege. It remains to be seen how the Santa Lucia Fir faired. Stay tuned.)

View looking north towards Cone Peak

Additional Photos

Additional Reading

Axelrod, Daniel I. “Evolution of the Santa Lucia Fir (Abies Bracteata) Ecosystem.” Annals of the Missouri Botanical Garden, vol. 63, no. 1, 1976, pp. 24–41. JSTOR, www.jstor.org/stable/2395221. Accessed 26 Jan. 2021.

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