Following in the footsteps of early explorers of southern Africa

In light of the upcoming Heritage Day in South Africa (September 24th), I decided to celebrate an element of our heritage that I find interesting, namely the excursions and encounters of some of the early British explorers. In the early 1800s the British were interested in expanding their influence around the world, including in Southern Africa, and a part of this endeavor was sending naturalists and explorers to collect information on the land, it’s people as well as on the local animals and plants. William John Burchell was one of these naturalists who has gripped my attention because of his fascinating character and because his exploration, discoveries, plant and animal collections and field notes have increased the knowledge of subsequent generations.

Burchell travelled to South Africa in 1810, arriving in the Cape of Good Hope in November 1810, and spent the next three years exploring the Cape, the broader Colony and the land beyond the borders of the area colonised by people of European descent at the time. His travels were undertaken for the purpose of “acquiring knowledge” of Southern Africa, including the local flora and fauna, as well as suitable areas to settle. In years following his time in Southern Africa, Burchell published a very detailed account of his travels in two volumes of his famous journal, Travels in the Interior of Southern Africa (see the title page above). I have read both volumes and found them highly engaging; full of fascinating details about life in Southern Africa at the time. For example, Burchell’s notes describe some of the plant species that he came across, including several species that were unknown to European naturalists at the time:

In addition to the extensive notes on natural history contained within the journal, Burchell also published a map and made hundreds of sketches. Some of these sketches were published in the journal in the form of woodcut vignettes, adorning the headings or end of the chapters. Now, before embarking on the long expedition throughout Southern Africa, Burchell explored the Cape region in a few local trips. Two of the vignettes in his Travels depict scenes from a short journey that Burchell undertook to Tulbagh, a small farming town located about 120 km from Cape Town (see map). I was intrigued to figure out whether I could reproduce some of the scenes, so I undertook a similar journey (not in an ox-wagon) to see what I could find.

Two of the scenes from Tulbagh depict the Drostdy and the main street in the Village. About the former Burchell wrote: “At a distance of half an hour’s walk northwards from the village is the Drostdy. This is a large and handsome stuccoed building, ornamented in front with a portico of three arches, to which the ascent is by a flight of steps. It contains several large and lofty rooms, together with a spacious council-room in which public meetings and the sittings of the judges at the annual circuit are held.”

I managed to place myself in almost the precise location that Burchell must have stood, although the trees have grown a bit since he drew it! In addition to the ravages of time, the Drostdy has survived a fire (in 1938) and an earthquake (in 1969). Part of the building has been restored, although I am not certain which bits are the original…so the restorer has done an impressive job.

The village scene was slightly more difficult to pinpoint, although still not terribly difficult because Burchell’s notes made it clear where he stood: “The village, as viewed from the parsonage-house, and looking southward.” A couple of things have changed in the intervening 210 years: The “row of young oaks along the street” have become much older and taller, obscuring the “mountains in the distance” (which Burchell referred to as the Roodezands Kloof, but I think they are the Witzenberg mountains?), and the mode of transport has also advanced. But nevertheless it is remarkable how little time seems to have changed the village:

I quite enjoyed stepping back in time, and found it quite engaging to place myself in the footsteps of Burchell. Doing so seems an appropriate way for me to celebrate my South African heritage, although the British explorers are, of course, only a small part of the wonderful, rich cultural heritage of the people of this great country.

Springing into action in Arbor week!

Spring has sprung in the southern hemisphere, although you wouldn’t believe it in Cape Town at the moment because it’s raining and cold. But, more to the point, this means that Arbor Week has begun! Arbor Week is usually associated with planting trees: I fondly remember planting young saplings at my school when I was younger. Although tree planting is something to be celebrated, trees are not the only type of plant that we should be planting. This is because trees do not occur in all environments (e.g. South Africa’s grassland areas or parts of the Succulent Karoo) and because trees are only one type of plant.

Take cycads, for example: cycads are seed plants (like conifers and flowering plants) with a very long fossil history spanning about 200 million years! Individual plants typically have a stout and woody trunk with a crown of large, fairly tough, evergreen pinnate leaves (like the individual above). Cycads were formerly more abundant and more diverse than they are today; their “hey-day” occurred during the Late Triassic or early Cretaceous epochs. Sadly, these unusual plants are threatened with extinction today, with many of the species having highly restricted geographic ranges and low population sizes. One species (Encephalartos woodii) is known to have only a few male individuals left, so is unable to reproduce sexually.

This year I am trying to cultivate a diverse range of plants, including cycads and restios. A friend of mine was kind enough to donate some seeds from an Encephalartos individual that is growing in his garden, and I was able to purchase some restio seeds from a local supplier. Let’s hope conditions get a little warmer in Cape Town, so they can germinate!

Western Leopard Toads migrating in Cape Town

The Western Leopard Toad is an endangered species (according to the IUCN) found mainly in sandy coastal lowlands in two disjunct areas of the Western Cape of South Africa: one close to Cape Town and another in the Overberg region. In those areas the toads live in gardens or in coastal lowland flats, but also in the adjoining valleys and mountain slopes. Every year the toads migrate toward local water bodies from the surrounding areas to breed, and this usually occurs in August after rain. Well, the toads are on the March at the moment!

Their biology is quite interesting. In addition to the annual migration to water bodies, apparently they can live for up to 14 years and reach a size of 14cm in length! That’s quite a toad! They also eat snails and small insects.

My wife and I consider it fortunate that a few resident toads live in our garden, where we often hear them croaking away. However, at the moment their croaks are being drowned out by the chorus of the migrants!

Flowers, flowers everywhere…

Every year the semi-arid and usually quite drab West Coast of South Africa becomes a carpet of flowers. This generally occurs in late Winter or early Spring (i.e. from mid August to early September) following the rainy season. Along the West Coast winters are generally mild and fairly wet in the south west, but conditions get drier as one moves further north toward Namibia. The flowers are especially prolific during years with higher rainfall. Because the West Coast has received very good rainfall this year, my wife and I decided to take a trip to see the show for ourselves. We drove to the West Coast National Park (about 2 hours drive from Cape Town) and were certainly not disappointed: the flowers are magnificent this year. There were several areas with standing water, indicating how good the rains have been (such as this pool, below) and carpets of red, orange, white pink and yellow flowers.

Annual plants, such as these daisies (above), are especially spectacular and are the stars of the show. I think most of the species are in the genus Arctotis, although daisies like these are notoriously difficult to tell apart (if anyone has a better identification please let me know in the comments). These plants tend to be herbaceous annuals that grow quickly, produce flimsy leaves and shallow roots with large flowers and survive most of the year (when the soils are dry) as seeds.

However, quite a few perennials (such as mesembs and Euphorbia below) also produce flowers during this time. Many of these plants tend to be succulents, surviving through the drier times of the year by relying on internal stored water.

Mesembs and Euphorbs are also notoriously difficult to tell apart, so I am not certain of these species either. However, I think most of the mesembs (also locally known as “vygies” because of the fig-like fruits that these species produce) are of the genus Lampranthus. I also think that the species below might be Euphorbia burmannii, because it is intricately branched and lacks the false flowers that I associate with Euphorbia mauritanica, a similar-looking species that is also widespread along the West Coast.

Not all succulent species flower with the rainy season. These species rely on stored water to produce flowers later in the season. One benefit to delaying flowering is that pollinators might be less distracted by the showy annuals!

Here is the wonderfully-named Euphorbia caput-medusae, which was locally common in the Rocherpan Nature Reserve (which I highly recommend to anyone planning a trip along this coast).

There were even a few parasitic plants, like this Cytinus sanguineus (below), which is a root parasite that has no leaves. The species has been placed in Rafflesiaceae, the same family as Rafflesia arnoldii – the species with the largest flower – but I think that the classification is uncertain at present (if anyone knows differently please let us know in the comments). I am not entirely certain why this species would be flowering now if avoiding competition for pollinators is highly important.

I must admit that even though flowers are not everything that there is to a plant, the allure of the annuals’ display is very hard to resist.

What is a tree?

“A tree is a big plant with a stick up the middle. Everybody knows that.” [Colin Tudge, The Secret Lives of Trees]

Everybody knows what trees are: Big, woody ent-like creatures that tend to form forests and house birds and bear fruit. A monkey’s playground, an elephant’s sparring partner and a rhinoceros’s back-scratching post. This all seems pretty obvious. But, what about the kokerboom (above) and the Aloe (below)? Are these trees?

The kokerboom seems like it should be called a tree; It just looks like one. It has a central stick-like feature and I could imagine a fairly small monkey hanging from those branches. The Aloe, on the other hand, seems too spongy and low growing to be a tree. But, then again, this raises the question must trees always be woody? Wood is often considered to be hard and rigid, rather than soft, fibrous and spongy, but kokerboom stems clearly fall into the latter category. They more resemble banana stalks:

“…they resemble palm trees, with a thick central stem and a whorl of huge leaves at the top. But the stem…is not of wood. [It] is formed largely from the stalks of the leaves, and its strength comes from fibres which are not bound together as in pines or oaks or eucalypts to form true timber; its hardness is reinforced, as in a cabbage stalk, by the pressure of water in the stem. So botanically the banana plant is a giant herb.” [Colin Tudge, The Secret Life of Trees]

Fortunately, the formal definition of wood helps us out. According to wikipedia, wood can be defined the following way:

Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic material – a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber.

Ok, so the kokerboom is a tree and the Aloe is a succulent shrub. Clearly, the difference between them is that the Aloe growth form is low growing and sprawling… But what about Microcachrys, the Strawberry Pine that creeps along the ground (see below)? It has a woody central stick, but it is very low growing and shrub-like. Must all trees be tall? What about bonsai trees?

Microcachrys creeps along in Alpine environments of Tasmania.

On second thoughts, it is not as obvious as it initially seems to define a tree. Everyone has their own definition and internal category. What is clear is that trees are not a single, well-defined group of closely-related organisms, but rather a collection of unrelated organisms that resemble a vague category that we have developed in our minds. In The Secret Life of Trees Colin Tudge defines a tree thus:

A tree is just a way of being a plant.

Urban space-seeker seeks natural awe.

This passage was clearly written prior to 2020; at a time before corona inspired lockdown measures had been implemented.

Today I had a brief sortie into the countryside for work purposes and jislaak! it was invigorating to get out into the wilderness again! Myself and a colleague (Abri de Buys) traveled to the Jonkershoek Valley just outside Stellenbosch for some field work. Jonkershoek is, of course, famous for being the site of one of the longest ecological experiments in the world:

In 1938 the South African government started a network of hydrological experiments at Jonkershoek for the purpose of researching the impacts of afforestation on water supplies. The experimental design was based on the classic paired-catchment principle…that the streamflow from two untreated catchments is compared, so as to establish their natural relationship. One is then planted with trees. The change in the relationship between the two catchments after afforestation could then be ascribed to the treatment or influences of afforestation.

SAEON is mandated with maintaining the micrometeorological stations at the various sites, and we were there mostly to do some calibrations and to switch out some equipment. But the site is also beautiful and I managed to snap some shots of the mountain flora and scenery. Take a look at these photos that I took on our day out to satiate (or frustrate?) your sense of wanderlust:

The Berg River catchment
Scattered Proteas
Protea neriifolia
Abri at one of the micrometeorological stations at 1200 m a.s.l.

Abri informed me that this rain gauge located at 1200 m above sea level (below) holds the record for capturing the highest annual rainfall in South Africa. I forgot what the total was…something close to 2800 mm I think. If anyone knows better – or has a link to a site that records this – please let me know in the comments.

Presentation on how we can use plant hydraulics to understand plant response to droughts

I recently presented my research on plant physiological responses to water deficit to the Institute of Soil, Water and Environmental Sciences. I have included a link to the presentation below for those who might be interested.

This was my first presentation to a virtual audience and it got me thinking about the future of science presentations and how we currently consume science. In general, I think it is important to continue to share research and engage on these critical issues and virtual platforms, such as this type of online seminar, is one way to do so. It will certainly take some getting used to and we have a lot to learn from other disciplines which are currently better at attracting and maintaining people’s attention. One avenue that might be worth be exploring is how to make these types of seminars more interactive. One of the things I found most challenging in this presentation was having to “engage” with a screen, rather than an audience. This is somewhat different to in-person seminars where the presenter can feed off of the audience and engage with individuals, which I enjoy doing. It might be worth playing around with this idea, such as by making the question time longer and possibly having more of a discussion rather a full length presentation? Perhaps readers will have some ideas, which they might want to share in the comments below.

Another aspect that I started to consider is that in-person science conferences can be an incredibly effective way of connecting people. I was invited to present by Uri Hochberg, who I met a few years ago at a conference on plant hydraulics in Maine, USA. Uri and I were postdocs at the time and there is plenty of overlap in our research interests. These kinds of connections are great to maintain. But I wonder how moving to an online mode of interaction might influence the capacity to develop these kinds of connections. On the one hand it is making it easier to communicate remotely, across vast distances. But on the other, it might be more difficult to develop connections, because these are often made at in-person conference sessions. Perhaps I am overstating the importance of in-person events? Again, let me know what you think; I’m curious to hear other thoughts on this.

In praise of plants, and the three-billion-year-old trap

When the light shone on the greenness, the greenness welcomed it, and comprehended it, and put it to use.” [Oliver Morton, Eating the sun]

The sunlight’s energy bounced from one molecule to the next like a frog across lily pads before reaching the subtle trap at the pool’s centre, the three-bilion-year-old trap where the light becomes the stuff of the earth.[Oliver Morton, Eating the Sun]

We need to talk about Kevin plants. I discovered this yesterday after having a revealing (and humorous) conversation with my lovely niece (5 years old; K) and nephew (3 years old; L), which went like this:

L: What are you doing today?

Me: Working.

L: What’s your work?

Me: Looking at plants.

K: Why don’t you do real work?

Me: …but this is real work. Plants are great.

K: But plants can’t do anything!

So I want to put the record straight! Plants are, in fact, the most fascinating creatures to study, and for any number of reasons: Plants power the planet, they have shaped Earth’s history and climate, they eat the sun, they produce most of the food we and other animals eat, they form the backdrop to the most beautiful views…the list is endless.

I am fortunate enough to be able to study plants for a living; one of the most rewarding career/life choices that I have made! Richard Feynman once wrote about the pleasure of findings things out…and I am constantly inspired by finding out new things about plants and how they function. I have been helped in this pursuit by many wonderful books, which I highly recommend. My top five books are: Eating the Sun (Oliver Morton), The Emerald Planet (David Beerling), The Secret Life of Trees (Colin Tudge), In Praise of Plants (Francis Halle), and The Wollemi Pine (James Woodford).

As a quick aside, the story of the Wollemi pine (not an actual pine, of course) is one worth recounting. Wollemia nobilis (which is closely related to the Auracaria‘s, or Monkey Puzzle trees!) is called a “living fossil” because it was first described from fossils, similar to the Coelocanth and the Dawn redwood. Living specimens of the plant were only discovered in 1994 (!) in a refugial valley in Australia’s blue mountains. Notice how similar the branches of the living plant are to the fossil specimens in the photo below, taken from The Wollemi Pine. Although the exact location of the natural populations is a well-kept secret, many plants have been grown in botanic gardens around the world since it was discovered. While I was in Australia I was lucky enough to see Wollemi Pines in the Royal Botanic Garden in Sydney in 2016 (see below) and in the Royal Botanical Gardens in Hobart.

So why are plants often under-appreciated? My theory, which is my own, is that us humans are biased towards focusing on things that stimulate or trigger our senses. We are hard-wired to pay attention to and appreciate movement and new noises, which is why birds and animals appeal to us. There is possibly an adaptive (or survival) element to this: animals and birds that grab our attention can be hunted and eaten. At the same time, we have also evolved to ignore less mobile and more common organisms or items because it would require too much energy to constantly focus on everything. The colour green is a good example: it is ubiquitous and constant during daylight hours. The three-billion-year-old chlorophyll trap works relentlessly while the sun shines to generate carbon-based products, and we would be hard pressed to acknowledge this incredible (microscopic) dance all the time.

The good news is that this under-appreciation can be over-turned. There are many ways in which the exciting world of plants can be brought to life. We can use our innate senses: Red excites us (because this is the color of ripe fruit…which is consistent with the survival aspect of interest that I mentioned in the previous paragraph), as do new smells from flowers. We can also observe plants in motion: seedlings growing towards the light, or the venus fly trap clamping down on a hapless fly. But more than that, we can learn new and exciting aspects about how plants work. Did you know, for example, that plants can have heart attacks?

Ode to oaks

One of the pleasures of comparative biology is exploring new places to find the organisms that are the focus of your research. During my postdoctoral research at the University of California, Berkeley I was fortunate to find myself in a position where I could explore the western part of North America in an attempt to better characterize the drought tolerance of temperate woody angiosperm trees. My study group was the wonderfully diverse oaks of North America. Nineteen species of oaks occur in the western part of the region (see Figure 1) and my goal was to figure out how they varied in capacity to withstand embolism (which I have written about previously).

Figure 1: Nineteen species of oaks (Quercus spp.) from western North America. A. Q. kelloggii (black oak); B. Q. agrifolia (live oak); C. Q. parvula; D. Q. wislizenii (interior live oak) E. Q. palmeri F. Q. chrysolepis (golden cup oak) G. Q. vacciniifolia H. Q. tomentella I. Q. sadleriana J. Q. gambelii K. Q. lobata (valley oak) L. Q. garryana M. Q. durata N. Q. berberidifolia (scrub oak) O. Q. pacifica P. Q. john-tuckeri Q. Q. douglasii (blue oak) R. Q. cornelius-mulleri S. Q. dumosa T. Notholithocarpus densiflorus (tan oak; not an actual oak, but a closely-related species)

As you would expect just by looking at the leaves of the different oaks, many of these species occur in vastly different habitats, including moist temperate rainforest (e.g. Quercus sadleriana; note the moisture on the leaves in the photo) and semi-arid desert scrub or chaparral (e.g. Q. berberidifolia) (see Figure 2). This meant that I had to sample species ranging from the pacific northwest close to the border between Oregon and California to the deserts of southern California close to San Diego.

The measurements that I was taking on each species involved drying the plants down from a hydrated state and visually capturing the point at which they fail (i.e. emoblise) using repeat photographs taken of the xylem. A key part of this measurement process is ensuring that the plants are hydrated when the measurements start. To ensure this I was required to collect the plants in the early hours of the morning, and then place them in a bag to prevent them from drying out. I also needed to take the measurements as quickly as possible from the time when I first collected the plants. The best way to ensure this was to make the hydraulics lab mobile! So, I packed up all the gear into my trusty steed (including scanners, pole pruners, pressure chambers, stem psychrometers and a whole bunch of other equipment) and hit the road (see Figure 3).

“I went to the desert on a horse with no name; it felt good to be out of the rain” [Americas]

On my travels I was accompanied by several incredible assistants, companions and collaborators. Together, we sampled oaks from all sorts of exotic locations. We sampled species in the high elevation deserts in southern California (note the snow), the pristine Channel Islands (we got there by ferry) and slow moving Los Angeles. It was very special to see exciting and diverse habitats and to meet many wonderful people along the way.

You will have to wait to see what we found…as that is a post for another day! One exciting initial finding though is the discovery that science moves at about the same pace as the traffic in Los Angeles (see Figure below)…