Quitobaquito

Along the US-Mexico border, about 15 miles west of the border crossing between Lukeville, Arizona and Sonoyta, Mexico is the small oasis of Quitobaquito in Organ Pipe Cactus National Monument. The shortest route to the site is a dirt road that, for much of its length, parallels the international border. In fact, in places it is no more than 20 meters from the metal fence on the US side, a barrier less formidable than many backyard fences. The saguaros and desert scrub take no notice of the artificial line in the sand so important to humans.

At Quitobaquito, perhaps a half kilometer north of the border, a tiny creeklet finds its origin in a spring that itself seems to just emerge from the base of a small non-descript slope of dry Sonoran Desert soil. The Park Service has lined the creeklet with concrete, no doubt to preserve the integrity of the waterway, because so minute is the flow that it seems like the desert dust could consume the trickle of water with no effort. As I walked along the creeklet, looking for its source, I could see signs of researcher presence – a short submerged PVC tube that I’m guessing houses a temperature sensor or other device, and some red plates underwater about which I cannot surmise their purpose.

Arriving at Quitobaquito (left) and some saguaro cacti near the oasis (right).

The creeklet ends in a rather large shallow pond to the south which is encircled by a narrow but dense band of sedges (just like Schoenoplectus americanus of west coast wetlands, though I’m not positive it is the same species). It looked like there was widgeon grass (Ruppia) in the water. The pond and creeklet were lined with colorful flowering species that I had not seen elsewhere in the Monument.

The pond at Quitobaquito. Sedges line the edge of the pond.

Why the effort to protect flow in the creeklet? This little oasis is home to an endangered fish species, the Quitobaquito pupfish (Cyprinodon eremus). I saw quite a few fish in the creeklet that led to the pond. The species is dimorphic in color – larger blue fish are reproductively mature males and females and immature males are smaller and light grey-brown, blending in well with the substrate. Incredibly these pupfish can tolerate high salinity, very high temperatures, and low oxygen conditions. The fish I observed were skittish and apparently territorial, chasing one another in short bursts of activity.

Quitobaquito pupfish. A arrow points to the female or immature male at left since these fish
blend in much better with the mud than the blue reproductive males.

Flowering plants near the pond: Heliotropium curassavicum (left) and Funastrum cynanchoides (right).

References

Reistad, A. 2012. Pupfish. In: National border, national park: A history of Organ Pipe Cactus National Monument, at: https://organpipehistory.com/orpi-a-z/pupfish/

Spellenberg R. 2012. Sonoran Desert Wildflowers. 2^nd ed. Falcon Guides, Guiford, MT.

Flowering plants near the creeklet: Anemopsis californica (left) and unknown pink-flowered species (right).

Arizona cacti

Heading east from San Diego I descended into the hot Imperial Valley and the Sonoran Desert. Ocotillos appeared signaling entry into this desert province. After a relatively cool spring in northern California, I wasn’t quite ready to be thrust into summer temperatures. My first major destination was Organ Pipe Cactus National Monument, just north of the Arizona-Mexico border. It lies right in the heart of the Sonoran Desert.

Organ Pipe and other cacti at Alamo Canyon.

Night sky at Organ Pipe Cactus National Monument.

I first visited Organ Pipe 20 years ago, when with a class of UC Santa Cruz students we descended on northern Mexico to study the ecology of the Gulf of California. The road to Sonoyta, Mexico passes bisects the monument. I arrived after dark, and turned up a dirt road to a small campsite at the head of Alamo Canyon. It was a warm evening. I stayed up for some time photographing landscapes dominated by Saguaro cacti. A half moon shone brightly in the sky above but was gone by 4 AM when I awoke again to photograph stars and the Milky Way.

With the new day, the diversity of cacti was evident from the start. Saguaros were very common, and organ pipe cacti became more common as I made my way up the valley for a morning hike. There were menacing cholla cacti, with their beautiful golden spines covering plants like a blanket. I also recognized the prickly pear cactus, Opuntia.

The organ pipe cactus (Stenocereus thurberi) is a collection of rather large stems, emerging from a common base. The namesake of the monument, the species is more common in Mexico than in the US and has a limited presence here due to its intolerance of frost. Flowers apparently only open during the night and are primary pollinated by bats.

Saguaros (Carnegiea gigantea) were actually very common at Organ Pipe Cactus NM, growing in most regions of the monument that I observed. However, there is a whole national park named in honor of this species, and that was my next destination. Bisected by the city of Tuscon, Saguaro National Park comprises two units east and west of the city. I briefly visited some of both, catching the sunset at the west unit and doing some morning hiking at the east unit.

Saguaro cacti. Left: spines (which are actually modified leaves on cacti) on a plant at Saguaro NP. Right: An open flower on a plant at Organ Pipe Cactus NM.

The morning of my hike started off warm. I began at a trailhead at Loma Verde and hiked about 2 miles into the Saguaro Wilderness along the Squeeze Pen and Carillo trails. Saguaro, barrel cacti, and Opuntia were common. Mesquite, palo verde (literally, “green stick”), and other trees and shrubs were also abundant in the area. At Wildhorse Canyon I found pools of water remaining in a wash.

Flowering cholla cacti at Saguaro NP. At left is the pencil cholla, Cylindropuntia arbuscula.

Though not a cactus, ocotillos were common at both Organ Pipe Cactus and Saguaro NP and were frequently in bloom, their bright red flowers adding color to the landscape. At Saguaro I saw many ocotillos with leaves (some green, some senescing), a sight that may not be particularly common since these plants readily shed their leaves during times when water is scarce. It is a true deciduous desert species.

Ocotillos. Left: With leaves at Saguaro NP. Right: Hummingbird visiting flowers at Organ Pipe Cactus NM.

Wildlife was fairly common at both of these desert parks. I saw coyotes (Organ Pipe), a Gila Monster (Saguaro), a hummingbird (Organ Pipe) and other birds, a deer (Saguaro), Desert pupfish (Organ Pipe), and lots of lizards (both parks).

Barrel cactus, Ferrocactus, at Organ Pipe Cactus NM.

Chainfruit cholla cactus, Cylindropuntia fulgida, at Organ Pipe Cactus NM.

An organ pipe cactus near the US/Mexico border that is half skeleton at this point.

Prickly pear, barrel cactus, and saguaros at Saguaro NP.

Sunset with Saguaro cacti and ocotillo at Saguaro NP.

California's marine biogeographic break

Felimeda macfarlandi, a chromodorid nudibranch at Cambria.

This month I’m repeating my spring road trip through the southwest, but oppostite of my general course last year, I’m first heading down the California coast. My focus is on marine life for a few days and then I head to the deserts and mountain ranges inland. Cambria was my first stop on Thursday morning on the central coast just south of Big Sur.

At Cambria, fleshy red seaweeds, surfgrass, kelps, and invertebrates filled out the rocky sandstone boulders and bedrock. I again saw a healthy population of the rockweed Pelvetiopsis hybrida, a seaweed I first encountered and wrote about last year. There were adorable small sporophytes of bull kelp in a handful of small patches in the low intertidal. One new find was a beautiful purple chromodorid nudibranch, gliding among leafy red algae.

Young sporophytes of Nereocystis luetkeana (bull kelp)
in the low intertidal at Cambria. Egregia menziesii is in
the background.

Friday morning I was at the Palos Verdes Peninsula in Los Angeles. Remarkably I have never been tidepooling in LA County despite growing up in the region and attending graduate school in San Diego. Pt. Fermin was my planned destination, but when I arrived there in the morning, all access was officially blocked off. Skirting around a barrier would have been no problem, but it didn’t seem advisable. Instead I drove a little farther north to White Pt.

Relatively strong surf pounded some high relief rocks in the intertidal just off the southern parking lot. I explored a section of coastline south of there, almost to White Pt. itself. The site was comprised of sandstone benches, boulders, and cobbles, a drab yellow color.

The changed character of the biota between central California and Los Angeles was immediately evident. I was struck with the incredible abundance of barnacles in the upper intertidal at White Pt. – a desert as far as macroalgae were concerned. Red fleshy seaweeds were essentially non-existent, and the large seaweeds (a few species of kelps and large brown algae) were generally limited to the low intertidal zone.

I had crossed a well-known biogeographic barrier by entering southern California, and the marine flora in particular indicated this dramatic change in biotic composition. Point Conception north of Santa Barbara is often regarded as the break; this is where the mainly north-south coastline of northern and central California bends toward the east to form the southern California Bight. North of Point Conception, water temperatures are cooler and there are pockets of coastal upwelling that bring nutrient-rich cool water to shallow depths for photosynthetic organisms to enjoy. The north-to-south California Current dominates the near-shore. South of the point, waters are warmer and the south-to-north Davidson Current is present. Hot and dry Santa Ana winds that blow from the northeast can bake the southern California coast.

A wave crashing into sandstone benches just north of White Pt., Los Angeles Co.

A cowrie at White Pt.

Desiccation stress, always a concern for aquatic organisms which are periodically exposed to air, may be more intense in southern California than in more northerly parts of the state. More intense sun, less rainfall, and warmer temperatures in southern California probably exacerbate desiccation stress in southern California.

I found the abundance of small barnacles in the high intertidal curious. These organisms must be hardy against desiccation – they are exposed to air most of the time after all – but I wonder how being clamped tightly shut most of the time affects their ability to capture food. They must open up and sweep the water in order to catch food particles.

Except for the low intertidal which is submerged often, tidepools were the other microhabitat at White Pt. where larger seaweeds were likely to be seen. Relative to the central coast, however, these were not particularly large, consisting of branching coralline algae, Gelidiales, and others. Small fish darted to hiding spots when they sensed me nearby.

Common low intertidal kelps north and south of Pt. Conception. Left: Laminaria setchellii at Cambria. Right: Eisenia arborea at White Pt.

One of the interesting kelps of southern California that is not seen farther north is Eisenia arborea. Its species name suggests “tree”, and that is not an inaccurate moniker. Eisenia is a small kelp species, born on a stiff stipe from which two sets of blades droop down in a sort of disheveled brown mess. At White Pt. it was almost exclusively in the low intertidal, with some stragglers a little higher up where pools were present. Eisenia also occurs in Japan. In central and northern California Laminaria setchellii takes its place in both overall form (though it is not such a mess) and in ecological niche. I’m curious to know if these species overlap in distribution at all, or where one begins exactly and the other ends. Some exploration of Santa Barbara and the northern Channel Islands holds the answer to that question I think.

Juvenile spiny lobster (Panulirus interruptus) in a tide
pool at La Jolla. It's carapace was about 3-4 cm long.

Today I was in La Jolla. The flora was different yet again, but more similar in overall growth form to White Pt. than Cambria. Eisenia was present, but so too was a small kelp, Laminaria farlowii, that I didn’t see in Los Angeles. These plants are simple ruffled blades, aggregating or growing as singlets in the low intertidal. La Jolla also had a remarkable contingent of brown seaweeds of the order Dictyotales. This group tends to favor tropical and subtropical regions globally.

At La Jolla I explored the area around Nicholson Pt., a series of sandstone benches between the posh homes and the Pacific. Ravines, and even an arch, were cut into the sandstone. In the mid and high intertidal were also pools of various depth and diameter – all providing a variety of microhabitats for marine organisms. The beautiful marine plants notwithstanding, today’s best find was probably a tiny lobster in the warm water of a pool in the mid-intertidal! I’m tempted to tidepool once more tomorrow morning, though I originally planned to leave early for Arizona. We shall see!

Zonaria farlowii (Dictyotales) was very common in low elevation
sandy tide pools at Nicholson Pt., La Jolla. This species grows in
elegant rosettes.

Pigeon Point intertidal

Pigeon Point in San Mateo County, CA is one of my favorite tidepooling
locations and I have visited this area for many years. In late March I returned
to the south side of the point. Here waves crash into rocks with a population of
the sea palm, Postelesia palmaeformis. The Pigeon Pt. lighthouse is in the
background.

Many of the palms exhibited desiccation stress, perhaps due to a combination
of mid-day low tides, warm sun, and wind. 

Another of my favorite kelp species on the California coast is this species,
Dictyoneurum californicum. It occurs as clusters of blades on rocks in
the low intertidal. I love the color and texture of the blades. 

At least two species of seagrasses in the genus Phyllospadix appear
to be present at Pigeon Pt. Here is P. scouleri underwater. It
occupied the low intertidal, often in channels between higher rocks.

Red seaweeds (Rhodophyta) are the stars of the show at Pigeon Pt. since they are in such high abundance relative to other seaweeds. Here is a sampling of species. From left to right is Osmundea spectabilis, Sarcodiotheca gaudichaudii (with some small epiphytic Microcladia coulteri), and a coralline alga - the most unusual "rhodolith" I've ever seen!

"Leafy" red seaweeds were relatively common in the low intertidal too. I
think this is one of the Botryoglossum species (Delesseriaceae).

Out on the rocks near the sea palms there were a few deeper tide pools
that had anemones, and high concentrations of purple urchins. 

I found a sculpin in one of these pools as well.

Finding this tube worm, Serpula columbiana, and photographing it underwater
was a treat. The colorful plume is used to catch food and accomplish gas change.
The operculum can be seen behind the the plume at top right. It is used to seal up
the tube when the animal retracts. Hat tip to my friend Allison Gong for the
species name. 

Incredible plants: Stenogramma

In some respects, red seaweeds (Phylum Rhodophyta) are the most interesting of the three major groups of marine algae inhabiting coastal shorelines. They are the most diverse seaweed group in temperate regions like the western US, they have fascinatingly complex life histories (that topic alone warrants its own post some day), and they occur in a tremendous diversity of growth forms and colors. They can be pink, brown, cherry red, or even greenish!

Generally red seaweeds are smaller and less ostentatious than the large brown seaweeds like kelps that sometimes dominate the intertidal shores of rocky temperate coastlines. But look under mats of surfgrass or in rocky crevices that are seemingly a little too dark for plant life – here you are likely to some of the more intriguing smaller red seaweeds. I came across one such species, Stenogramma californicum, in relative abundance during my exploration of Pfieffer Beach in Big Sur last month. This species has long been one of my favorite reds.

Stenogramma californicum underwater at Pfeiffer Beach, Big Sur, CA, Feb 2018.

The first thing to note about Stenogramma is that is has dichotomous branching. This means that each axis of the plant splits in two at a branching point, with each branch of equal length. Many red seaweeds have dichotomous branches, but Stenogramma has one other feature that makes it almost immediately jump out as distinct from other similar-looking species: in some plants it has thin white longitudinal lines that run down the center of each branch. These lines are actually present on female plants and are the locations where spores (carpospores to be precise) are produced after female eggs are fertilized. There are several orders of branching.

Stenogramma californicum is typically 6 to 20 cm in length. The flat dichotomous branches are up to 1 cm wide and have broadly rounded tips. According to Abbott and Hollenberg (1976) it is a relatively common plant in the northeast Pacific, occurring from British Columbia to Baja California. Related species also occur in British Columbia, Europe, South America, and Australia. In my experience it is not all that frequent along the NE Pacific coast, but there may be some good reasons I have overlooked it in the past: it is a smaller plant, it grows in the low intertidal to subtidal where it may be more challenging to find, and one can easily overlook species one is not specifically hunting for.

Herbarium specimens of Stenogramma in the UC Berkeley University Herbarium.
Left: a female plant, bar = 2 cm long. Right: a tetrasporophyte from Jalama Beach, Santa Barbara
County, CA, bar = 5 mm long.

On the north shore of Pfieffer Beach where I explored last month, it grew in the low intertidal, with or without the cover of surfgrass. The female plants were relatively common. I suspect there are many unanswered questions about the natural history of Stenogramma and smaller seaweed species like it. How long do plants typically live? Which herbivores graze on them? Does Stenogramma produce anti-herbivore compounds? How far do spores travel? How quickly do newly settled spores grow on a rocky substrate? What is the ideal amount of light? How much gene flow occurs between populations that may be separated by kilometers? 

Another plant underwater with articulated coralline algae at Pfeiffer Beach, Feb. 2018.

For smaller species like Stenogramma that may not have immediate economic value, or which don’t play major structural roles in coastal ecosystems (e.g., kelps), it may be hard to find the funding to study many questions about their natural history and ecology. Yet these smaller species, like all others, hold tremendous natural history value. They are each literally a wealth of millions of years of evolutionary innovation, holding some stories that will be forever lost to time, and revealing other stories that will enrich those who seek to know them better.

References

Abbott IA, Hollenberg GJ. 1976. Marine Algae of California. Stanford University Press, Stanford, CA.

Gabrielson PW, Lindstrom SC, O’Kelly CJ. 2012. Keys to the seaweeds and seagrasses of southeast Alaska, British Columbia, Washington, and Oregon. Phycological Contribution Number 8.

Jade Cove

Monday 26 Feb 2018: Big Sur revealed its different faces today as a morning overcast sky gave way to drizzle, rain by early afternoon, and finally brilliant winter sun and crisp wind. Tonight clouds pass over a nearly full moon rising before sunset from the east, the short storm having now moved on. The bright stars of the Big Dipper are visible to the northeast. It is quiet in southern Big Sur, the temporary end of highway 1 just a few miles more to the south. The road closure and winter perhaps isolate this area a bit more than usual.

Jade Cove and the southern Big Sur coastline.

The low intertidal kelp, Laminaria setchellii with surfgrass,
Phyllospadix, in the background.

The low tide this afternoon was good, uncovering the kelps, surfgrass, coralline algae, and invertebrates of the rocky coastline of Big Sur. I was wet due to rain from above and surges of surf from below, but excited as a climbed over boulders to explore a new site. This was the area of Jade Cove – picked over by divers for the heavy nephrite jade – though I was there principally for the seaweed gems. The little cove was accessed by a steep and unstable trail from the bluffs south of Sand Dollar Beach.

At the lower tides, a cluster of large rocks towards the center of the cove were accessible by hopping like steppingstones across several slippery boulders covered in emerald surfgrass. Inshore of these rocks in an area somewhat protected from the full impacts of the incoming surf, there was a small population of a large brown seaweed Stephanocystis osmundacea (not a kelp, but typically growing with them) inhabiting the low intertidal and shallow subtidal zones. Despite the relentless pounding of surf here, some of these rocks were jagged and sharp with deep crevices, sort of like a geologically young mountain range thrust boldly into the sky, ignorant of erosive forces that will eventually smooth them.

Black abalone.

In these crevices I found several dozen black abalone, their smooth dark shells pressed against the rocks protecting a soft body beneath. They were wedged as far away from surf or predators as possible. The abs were of various sizes from a few centimeters long to about the size of my hand. There was also a lone red abalone of similar cryptic disposition in the low intertidal.

Across the cove, the kelps Laminaria setchellii and Egregia menziesii were the dominant large brown algae of the low intertidal, the blades of former species like little golden brown flags drooping from short flagpoles. Patches of purple sea urchins (Strongylocentrotus purpuratus) and the general dominance of pink coralline algae in the low intertidal suggested a harsh world for the fleshy red seaweeds which can otherwise dominate the low intertidal at other sites in central and northern California. There were some specimens of Chondracanthus corymbiferus and Prionitis but the lacy red seaweeds of the Delesseriaceae seemed generally missing from the algal community.

Offshore some large floats of bull kelp (Nereocystis luetkeana) rolled with each incoming well. These plants are last year’s stragglers since this species is usually an annual. Farther offshore still, signaling perhaps the presence of a shallow reef hundreds of meters from shore, was evidence of a canopy of giant kelp, Macrocystis pyrifera. I counted perhaps 10 individuals of this same species in the low intertidal and shallow subtidal along the shore, separated from their offshore family.

Some sea caves in Jade Cove. Stooping, I walked through the one on the right.

As the rain of the early afternoon let up and the sky began to clear, there was a band of puffy white cumulus clouds bunched together low on the horizon over the sea. The sun broke through with the rising tide and being quite wet and very cold I was decidedly done exploring the intertidal. I had enough coordination left to climb the steep muddy trail back up to the bluff some 200 feet above. I walked around the bluffs for a time slowly warming in the sun. The wind kept up all afternoon and was especially strong at the crest of the bluffs which afford the most incredible views of a majestic unrepentantly wild coastline. 

An early California spring

The last week has been rather warm in California, and today was exceptionally so. I admit that the warmth is very pleasant, but it is way too early for 70°F highs in northern California. Indications are that this warmth may persist for some time with California and the rest of the Southwest remaining quite dry for the month.

Weather of course is not climate, but as spring conditions trend towards occurring earlier year over year, this is a strong indicator of climate change in action. Out here in the western US, the exceptional warmth coupled with low rainfall may exacerbate drought conditions. California traditionally has highly variable rain patterns (of all states in the US it has the greatest year-to-year variation in precipitation), so swings from last winter (when precipitation was well above average) to this year (where we are rather below average) are to be expected.

I wanted to take advantage of the pleasant weekend and went on a short hike today to the Stebbins Cold Canyon Reserve in the coast range near Winters, California. Unsurprisingly a lot of other people had the same idea. Few plants were in bloom yet, but ferns and shrubs were thriving. A little ways up the trail into the canyon, there was a small amount of cool water in the creek, perhaps soon to dry up if February remains dry. I photographed water striders which posed on the surface tension of the water, active in the warm sun, leaving oversized shadows on the smooth rocks in the creek bed. 

Water strider shadows in the shallow creek.  

One of my newest favorite trees, the California bay laurel (Umbellularia californica) was in bloom along the trail! At the base of its spatulate leaves there were small clusters of yellow flowers. The flowers had a pleasant smell, different from the equally pleasant smell one obtains by rubbing the leaves of the plant through one’s fingers.

Blooming bay laurel.

It remains to be seen if an early spring is really here in California. If so perhaps we will begin to see blooms in short order on the almonds, peaches and other stone fruits prevalent in orchards of the central valley. Typically almonds will begin to bloom in mid February, shortly before my birthday, followed by other Prunus species. In the foothills, an assortment of wildflowers may soon be on display.

This coming April I’m hoping to take a road trip through the southwest, another version of the really memorable trip I completed in April of 2017 that took me to some exceptional national parks and monuments. If conditions are much drier this coming spring than last year, it will be interesting to see if the effect is noticeable. For example, last year I recalled seeing snow on the transverse ranges through central eastern Nevada, and a greener than expected landscape in that state. I experienced rain showers as I camped in Moab, Utah and backpacked in the Petrified Forest in eastern Arizona. 

One of the few blooming species at the reserve.
It superficially resembles a paintbrush, but I'm not sure
what this species is.

The breakwater forest

Giant kelp beneath the kayak near the Monterey
Breakwater.

A good series of low tides often falls around the turn of the new year and so was the case for the beginning of 2018. Winter days are short, but in California the spring low tides of the winter often occur in the afternoon, enabling a good trip if weather and swells are favorable. A trip to the coast was in order and for two days I had excellent tidepooling excursions to rocky shores near Pistachio Beach in San Mateo County and at Carmel Pt. south of Monterey.

My past several visits to Monterey over the course of the year taunted me with seemingly calm conditions on the eastern side of the Monterey Peninsula because I had failed to bring the kayak. Not to be stymied again, for this trip to the coast I determined I would bring the boat along. Approaching the peninsula yesterday morning, conditions seemed promising again. On New Year’s Day morning during a high tide I launched from the thin strand of sandy beach at the Monterey Breakwater, more officially known as San Carlos Beach.

The Breakwater is well known to me, as well as many other SCUBA divers, because it is a frequently-visited location for recreational diving, including beginning courses. There is marine life on the breakwater rocks, a subtidal eelgrass meadow, sandy bottoms, and a giant kelp forest (Macrocystis pyrifera) offshore of Cannery Row. It is part of the Ed Rickett's State Marine Conservation Area.

A curious sea otter.

The waves were manageable yesterday so I launched from the beach, though there was more chop and wind than would have been ideal. I didn’t venture far, but circled around the kelp forest, paddling intermittently to maintain position. Few kayakers or divers were out. My kayak is more suited for calm riverine or estuarine paddling, but can handle milder ocean conditions.

Five, perhaps six, sea otters occupied the same kelp forest that I spent time in. The animals generally kept their distance, but peered curiously at me during breaks from their routine of diving below the surface to hunt for food. Some black cormorants flew low over the water.

I was reminded of the difficulty of photography while kayaking. The constant motion of the kayak precluded having much time to compose thoughtful shots. The otters were too far away for any excellent above-water photos with the waterproof camera. Below the surface, the main subjects were kelp and Chrysaora, a purple jellyfish that has been abundant at the breakwater on my last two visits to Monterey. As the kayak lumbered over swells and drifted in currents and wind, I plunged the camera into the water over the side of the kayak and took stabs in the dark, so to speak, of kelp and jellies at various angles. Remarkably, a few shots turned out fairly well! 

Jellies of the genus Chrysaora at the water's surface.

Macrocystis pyrifera is the dominant canopy-forming species
in most kelp forests in central and southern California.

Incredible plants: giant sequoia

General Grant tree in the Grant Grove, Kings
Canyon National Park, 2014.

California is a land of superlatives, and especially so botanically. Trees are at the top of the list for California’s record breaking plants: the state is home to the world’s oldest trees (the bristlecone pines, Pinus longaeva), the world’s tallest trees (coast redwood, Sequoia sempervirens), and the world’s largest trees by volume (the giant sequoia, Sequoiadendron giganteum). Each of these record-setting trees occurs in different geographic areas and environments among California’s diverse set of geologies and climates. They are all conifers, a widespread group of gymnosperms (gymnosperms are seed-bearing, but flowerless, vascular plants).

The giant sequoia has a narrow geographic range, found solely on the western slopes of the Sierra Nevada range in central California. It occurs across a fairly broad range of elevations (825-2700 m), though most populations of the species lie between about 1800 and 2100 m above sea-level (Yu et al. 2017). Upper and lower elevations of the species may be limited by low temperatures and low precipitation respectively. The coast redwood is distributed in the coast ranges from central California to southwest Oregon. It typically grows at much lower elevations than the giant sequoia and generally in close proximity to the coast with its cool and foggy maritime air.

The coast redwood is believed to be the closet living relative of the giant sequoia. Both species are classified in the conifer family Cupressaceae which includes cedars, junipers, and cypresses. Metasequoia glyptostroboides (the dawn redwood), which occurs in China and was only discovered within the last century, is a cousin to the two California redwood species. Fossil evidence suggests that redwood-like trees were formerly much more widespread in distribution across the Northern hemisphere. Sequoiadendron for example, may have been distributed in the past in North America, Europe, and New Zealand. Thus, these three redwood species might be considered relict species with greatly constricted modern distributions relative to the past. Perhaps glacial cycles (increased northern latitude ice cover implicated in the case of Metasequoia) and other factors over time have led to the range constriction of this group of conifers.

Hypothesized evolutionary relationships among giant sequoia (Sequoiadendron giganteum), coast redwoods (Sequoia sempervirens), the dawn redwood (Metasequoia glyptostroboides) and other Cupressaceae. Tree after Kusumi et al. 2000. 

The giant sequoia is a behemoth, estimated to be greater in volume than any other tree species in the world. The largest individuals have an imposing presence in the mixed conifer forests in which they occur. The base of the trunk in the largest individuals can often reach up to 11 m in diameter and 90 m in height (a little shorter than the coast redwood). The giant sequoia has reddish fibrous bark like the coast redwood, with deep furrows evident in older, larger trees. Old growth individuals may live several millennia.

Needles and cones in the giant sequoia and coast redwood are different enough to enable easy identification (in addition to differences in native range between the species). The giant sequoia has short pointed leaves that emerge from stems in a radial fashion, whereas most leaves on the coast redwood are pinnate sprays of leaves flattened in one plane. (An interesting exception is the leaves at the very top of a coast redwood which look quite similar to giant sequoia leaves in overall form.) Giant sequoia trees have both male and female cones on the same individual. Female (seed-bearing) cones of Sequoiadendron and Sequoia are both egg shaped and similar in morphology, but cones of the giant sequoia are about twice as large, almost the size of a chicken egg. Female cones of the giant sequoia are produced in clusters high in the foliage and bear small papery seeds a few centimeters in size.

Foliage of giant sequoia (left) and coast redwood (right). Photos from Bearskin Grove, Sequoia National Forest (2014) and Ventana Wilderness, Los Padres National Forest, Big Sur (2015).

Female cones and seedling of giant sequoia, Tuolumne Grove, Yosemite National Park, 2017.

Several giant sequoias with other conifers in the
Tuolumne Grove, 2017.

Fire is a necessary ecological disturbance for the persistence of the species. Unlike coast redwoods which can grow semi-clonally (e.g., from burs), sequoias generally only produce new individuals from seed, though new shoots can develop from injured stumps in younger trees. Mature trees are resistant to fires of low to moderate intensity which remove understory plants and favor sequoia seed germination by exposing bare soils for germination and increasing light levels reaching the forest floor. When occurring in mixed conifer species forests, sequoias are often found with sugar pines (Pinus lambertiana) and white firs (Abies concolor). Lack of fire will promote white fir relative to giant sequoias.

Controlled fire is used today by some agencies to manage sequoia groves. Reducing woody biomass in the forest understory is a means of protecting groves from more intense large scale-fires made more likely by decades of fire suppression practices in the western US. 

With its immense size, the giant sequoia was a prized timber species in the 19^th century. Many of the 67 groves of living giant sequoia are currently protected on state or federal land. This includes three groves in Yosemite National Park and many groves in Sequoia and Kings Canyon National Parks. Additional groves within Sequoia National Forest were protected from commercial logging (which occurred up until the 1980s) with the creation of Sequoia National Monument in 2000. The groves vary greatly in size, old-growth forest extent, and logging history. The smallest of all groves is also the most northerly grove in Placer County west of Lake Tahoe. It has only 6 trees.

Panorama of the Muir Grove in Sequoia National Park, 2014. The sequoias are clustered at top center and can be distinguished from other conifer species by their slightly yellow-brown color and bushy crowns.

Sequoias are vulnerable to root disturbance and intense fires. Climate change might also present challenges to the species persistence, possibly through increasing drought impacts in the future in the Sierra. For instance, recent work by Yu et al. (2017) suggests that drought impacts may be more severe in sequoia groves than in nearby forests dominated by other tree species. However, Willard (2000) suggests that groves have been doing well recently, with many recovering from historic logging and some expanding in size.

References

Baldwin BG, Goldman DH, Keil DJ, Patterson R, Rosatti TJ, Wilken DH. 2012. The Jepson Manual. Vascular Plants of California. 2^nd ed. University of California Press, Berkeley, CA.

Eckenwalder JE. 2009. Conifers of the World. The Complete Reference. Timber Press, Portland OR.

Kusumi J, Tsumura Y, Yoshimaru H, Tachida H. 2000. Phylogenetic relationships in Taxodiaceae and Cupressaceae sensu stricto based on matK gene, chlL gene, trnL-trnF IGS region, and trnL intron sequences. American Journal of Botany 87:1480-1488.

Su Y et al. 2017. Emerging stress and relative resiliency of Giant Sequoia groves experiencing multi-year dry periods in a warming climate. Journal of Geophysical Research: Biogeosciences 122:3063-3075. Preprint link.

Weatherspoon CP. 1986. Silvics of giant sequoia. In Weatherspoon et al. Proceedings of the workshop on management of giant sequoia; May 24-25, 1985; Reedley, California. USFS General Technical Report PSW-95.

Willard D. 2000. A Guide to the Sequoia Groves of California.Yosemite Association, Yosemite National Park, CA.

Sequoias in the Muir Grove, 2014.

Cluster of female cones (left) and close-up of trunk (right), Tuolumne Grove, 2017.