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I'm Erika Zavaleta and this is Ecosystems of California.

Im at Big Creek Landels-Hill Reserve in Big Sur in the Central California Coast.

Part of the UC Natural Reserve system.

And here where I am standing high on Eagle Trail almost directly above the Pacific on

a southwest facing ridge is the prime example of coastal sage grub.

An ecosystem type that's truly diverse.

And marked by a combination of wild flowers and

shrubs that are aromatic like artemisia and salvia.

Coastal sage scrub despite it's name

can occur as far as a 100 kilometers from the Pacific.

It's primarily a southern half of California ecosystem type.

So it happens is far north is just north of the San Francisco Bay area and

extends all the way South to the Mexican Boarder.

While similar to chaparral in the fact that it's dominated by shrubs,

coastal sage scrub vegetation differs in at least one key way.

While chaparral vegetation is mostly evergreen

holding on to it's leaves year round.

Coastal sage scrub shrubs are either drought deciduous,

dropping their leave in the summer, or they produce dimorphic leaves.

So, they'll grow larger leaves in the winter, and then drop them, and

put on smaller summer leaves out of axillary chutes.

Why the difference in strategy between coastal sage scrub and chaparral?

One possible explanation is that soils in coastal sage scrub ecosystems tend to be

much more rich in nitrogen than soils in chaparral systems.

So if they're two to three times more nitrogen rich,

it can makes sense to have a strategy in which you drop your leaves every summer,

like we are seeing right now, in order to avoid losing moisture during the drought.

And then put on new ones using some of that soil nitrogen every winter.

Whereas in chaparral where nitrogen is scarce,

the better strategy might tend to be one where you hold onto your leaves and

don't have to access and scavenge for nitrogen to build new ones every year.

Here, in Big Sur, chaparral and

coastal sage scrub both occur in hot and dry water limited sites often on south and

west facing slopes, kind of like the one that I'm on now.

But the drought deciduous habit allows coastal sage scrub dominance to reduce or

cease photosynthesis during the dry summer, and

then resume it during the mild coastal winters.

Related to the feature of summer dormancy in coastal sage scrub

is the feature that most coastal sage scrub dominants have much shallower roots

than the chaparral shrubs that dominate those systems.

So coastal sage scrub plants are less able to access ground water during the summer

to continue to fuel high levels of photosynthesis.

Coastal sage scrub harbors relatively high densities of small mammals,

things like mice and wood rats.

They benefit from the cover provided by the shrubs to protect them from predators

and also from food that's available under the shrubs and between them.

And small mammals in turn can accentuate plant diversity in coastal sage scrub by

feeding in and clearing the spaces between shrubs.

And by doing that they create the conditions for a new shrub ceilings to

establish, potentially a new species, as well as new species of small wildflowers.

However, invasive species of plants are also

increasingly common in coastal sage scrub, and they can take advantage

of the cleared areas provided by small mammals to establish.

And although invasive plants such as the grass, Avena barbata or

wild oats from Europe, can't really compete against adult shrubs, they can out

compete the tiny shrub seedlings that would emerge in those open spaces.

And so, exotic species can take advantage of disturbance by small mammals as well as

disturbance by things like fire or clearing for

development to establish a foothold.

And over time ratchet towards dominance by more annual species and by more exotics.

Fire is not a very frequent part of coastal sage systems because lightning

historically has been pretty rare at the coast.

But fire is an important part of these systems burning historically

on the order of every 30 to 100 years and

you can see that in some of the adaptive strategies of the plants here.

Some of which have seeds that are germinated by fire and

others of which can do things like resprout following fire.

Although that's much common here then in chaparral systems that extends

further into the interior of the state and can be adapted to more frequent fire.

Although coastal sage here in Big Sur is a relatively protected ecosystem type,

much of its distribution is in Southern California where it's threatened by

a combination of development as well as invasive species and nitrogen pollution.

Coastal sage scrub tends to occur on these sloping coastal habitats in warm climates.

And those are the same places that are popular for urban and for

agricultural development.

Invasive species get introduced more into places that are visited more by people.

And these are popular for recreation, especially in Southern California.

So those invasive species are challenging systems of coastal sage in the south.

And then they are also exacerbated by the presence of nitrogen pollution,

both from point sources like industry and from non-point sources like automobile

exhaust, which fertilizes soil further and make it more beneficial for

the highly competitive strategies of the invasive plants.

Nevertheless in a place like this at Big Sur, coastal sage scrub continues to be

a really, really thriving ecosystem type with on the order of 200 different species

of flowering plants and maybe 20 times that many fungal species in the soil.

That's a big feature of the system that remains pretty poorly studied.

So there are lots of opportunities for conservation and for

research in coastal sage systems.

And as you can see in places like this, they're a really,

really important stabilizing the steep slopes that characterize the southern half

of California's coastline.

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Coastal Sage

Ecosystems of California

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