I am a research scientist investigating the physiological responses of plants to water limitation. I am currently a Future Leader of African Independent Research (FLAIR) Fellow at the South African Environmental Observation Network. I completed my PhD at the University of Cape Town (South Africa) in 2014. My dissertation was an investigation into the role of plant hydraulics in determining the response of Fynbos to drought. After obtaining my PhD, I conducted postdoctoral research at the University of Tasmania (Australia) for two years. I examined the physiological factors that influence gas exchange in plant communities. I subsequently accepted a position as a post doctoral researcher at the University of California Berkeley (USA), examining fundamental questions in plant physiology and ecology.
In my spare time I enjoy appreciating nature, particularly interesting plants, and thinking about evolution. I think people benefit tremendously from having forests and natural plant communities to explore, and think we should do more to promote their conservation.
View all posts by Rob Skelton →
South African plants are set to receive their share of the limelight! A new television series will uncover the secrets of our indigenous flora, by describing stories of plant evolution and diversity! I can’t wait to tune in, especially because the first episode is on Fynbos.
WARNING! High species diversity ahead! I recently travelled to the South Africa’s Eastern Cape Province to conduct some field work with Daniel Buttner and Alastair Potts of the Nelson Mandela University in Port Elizabeth (Alastair is an ecologist and lecturer and Daniel is a postgraduate student in the Botany Department at NMU). The trip has involved working in some of the most remarkable plant communities, or biomes. You can think of a biome as a type of close-knit community of many different species interacting more closely with one another than with species from other biomes. For example, types of temperate forest or mangrove forest are different biomes. What is remarkable about the biomes of the Eastern Cape is that they are often found in very close proximity to one another. One small reserve that we travelled to contained about six different biomes, meaning that there were six different plant communities all operating independently but with very sharp boundaries between them! This results in an incredibly rich diversity of plants in a very small region, all doing slightly different things. The edges of the biomes (also known as biome boundaries) are controlled mostly by soil type, fire and climate.
Perhaps the most unusual of these biomes is the Thicket Biome, consisting of stunted (low growing) trees and succulents. The plants of the Thicket Biome are incredibly dense (as the name suggests), and also often spiny, so it is hard work making ones way through a patch!
WARNING! Distressing images of stressed trees ahead! The goal of the trip was to assist Daniel in quantifying water stress levels of Pappeacapensis trees, to help determine how severely impacted they are by the current drought in the region. It has been very hot and dry for several months and many of the plants are showing visible signs of distress or have died (although it is currently raining as I type this!).
In addition to the obvious signs of distressed plants (and on a more positive note) I have been most impressed with the diversity of plants and growth forms in the area. It is wonderful to see an abundance of succulents and low growing trees, and even patches of fynbos most commonly associated with the Western Cape Province growing high up on sandstone-derived soils. It was also my first time experiencing a cycad forest, which (as Daniel noted) felt a bit like walking through Jurassic Park! Some areas even had cycads growing next to fynbos species.
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.
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!
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!
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.
“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?
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:
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:
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.
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.