MARCH 2022
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Although the summer begins to wind down, the rainfall was still steady during March with 170mm falling over the office, a good 50mm higher than the annual average for March over the last twelve years. This rainfall figure brings the central part of Finsbury 20mm above the average annual rainfall figure of 900mm. The rivers, although flowing nicely, are not flowing strongly and that could be attributed to the fact that the catchment areas have seen significantly less rainfall than the office area. The north and east of the estate records around the 800mm mark while the southern part only records 676mm. The north, east and south are important because it is in the mountains there where lie the aquifers that feed our streams and so, although the rainy season has been very beneficial environmentally for the well-spaced and absorbing rains experienced, more rainfall is required in the mountains in these areas to adequately fill the aquifers so that our streams flow nicely during the upcoming dry months. These nice, well-spaced and absorbing rains have certainly caused the vegetation on the estate to flourish and the scenery is spectacular. Like, how spectacular is the display provided by a colony of Narrow-leaved Nerines beside the Majubane waterfall in the photograph above. Always special flowers blooming in the spray of this magnificent waterfall! Below is a bunch of interesting wildlife I encountered during the month:
After completing a rather grueling hike and returning to my bike in Hidden valley the other day, I lay down to take a refreshing drink of pure, chilled mountain water from the Klipdrif stream. I suddenly heard this loud thrumming sound approach me and when I got up, this African Hummingbird Hawkmoth, Macroglossum trochilus, gently approached my face and began drinking the sweat from my hairline! It was an almost spiritual experience with the soothing, deep thrumming sound in my ears and the wind from its wings cooling my face. It seemed so peaceful and trusting as it moved from my brow to the straps of my backpack which were also drenched in salty sweat. I removed the backpack and put it down on the grass and the Hawkmoth hovered over it as it drank away, allowing me to get this close-up shot.
The main food for this insect is the sweet nectar produced by flowers but they will also enjoy a meal of the juices of a rotting corpse or fresh excrement where other nutrients are found. Or maybe the salt present in sweat. Being nectar feeders, they, with their long, straw-like proboscises, are perfect candidates as pollinators for plants with flowers designed to attract specialist pollinators. This specialist pollination strategy, as opposed to a generalist pollination strategy, is employed by some plants to minimise the chance of the stigma (female pollen receptor) being clogged by the pollen from other plant species, which would be introduced by generalist pollinators. The plants that choose this strategy have opted to produce flowers with a design that only allows pollinators with mouthparts the length of their corolla tube or longer to access the nectar, which lies at the bottom of the corolla tube. All pollinators with longer proboscis' than the corolla tube will still be able to access the nectar, but will not collect pollen from the stamen of the flower because they will not touch it with their body because it is too far away. So, when this Hummingbird Hawkmoth drinks pollen from a flower with a short corolla tube, it will not collect pollen. It will only collect pollen from a flower where the it's face touches the male parts of the flower, ensuring that the it only carries the pollen from a small range of flower species, even if it visits many other different flower species during feeding. This makes it the "specialist pollinator" that the flower is designed to attract, increasing the chances that the following flower where pollen is transferred, is the same species of flower. Certainly a gentle soul with an important job, this Hummingbird Hawkmoth.
This spectacular butterfly, a Green-striped Swallowtail, Princeps nireus, also has sucking mouthparts a similar length to the Hummingbird Hawkmoth but its inability to hover as efficiently as the Hawkmoth restricts the types of flowers whose nectar it can access because it needs a foothold. And you can see here, as it drinks nectar from the flowers of a Tropical Slugwort, that its body doesn't come close to the flower parts so will not pick up pollen except randomly on its feet. Not benefitting the slugwort at all. But the butterfly, although rather common here on the estate, is hard to get a good look at because it rarely sits still for a second! The flash of blue-green catches one's eye as it zips from one flower, hovering awkwardly and grappling with its legs while it quickly sucks up some nectar, to the next flower, flashing the brilliant green-blue (depends on the angle) stripes on its fluttering wings. Even when it flies in the shade, the contrast of it's pitch black body and the brilliant blue-green stripes on the upper wings shines in the darkness. Almost as if it is generating light. It almost is really, if you look at it from our perspective, because the colourful scales on the wings are flourescent. That means that, when they absorb light with very short wavelengths (Ultraviolet), a dark light that our eyes do not see, the scales reflect a light with a much longer wavelength, light that we can see! So yes, the scales on the butterfly's wing patterns are actually generating light for ours, and many predators' eyes to see. But the strobe effect and the erratic flight path of the butterfly make it a confusing quarry. In fact, almost the only time one gets to see this butterfly sitting relatively still is when it, usually in groups, sits on the floor sipping the fluids from excrement, carcasses and the like. But the wings still shiver franticly while it does this.
Two years ago, right at the beginning of the original lockdown, I featured one of these truly alien-looking fungi, a Starfish Stinkhorn, Aseroe rubra, in one of my blogs but I must show you again. Initially, the mushroom looks like a puffball mushroom sitting amongst moist leaf litter and this has the descriptive name off the "egg". The egg then cracks open on the top and opens up, revealing a slimy interior out of which the stem grows and once it has reached about ten centimeters, the bright red tentacles open up to reveal a topping of dirty brown slime, called the gleba. The gleba is a slimy substance in which the spores are produced and it smells of dead meat which completes the picture of an open, rotting wound. A perfect attractant to bot flies and the like who spread the spores after they land on the mushroom and the slime adheres to their bodies. This was the very first indigenous mushroom described from Tasmania and was collected in 1792 and described in 1800. Soon after that, it was introduced to Europe and ultimately North America. It is believed that it was introduced to all the places where it now exists outside of Tasmania and Australia although Mycologists are not sure regarding Southern Africa because here it has been found far from human influence and bot flies have a limited range during their lifetimes. Aseroe comes from Greek for "disgusting juice" and rubra is latin for red so both common name, Starfish Stikhorn and the scientific name are very descriptive..
Finally, this is a photograph, taken on the Rock Kestrel trail, facing north east about two kilometers in, of the grasslands after a Patch Mosaic Burn (PMB) that I burned from the seventh to the ninth of March. I would like to try and briefly explain the function of grasslands in the greater scheme of things and the pros and cons of burning them. It is quite a long explanation but it is not possible to make it more concise, I'm afraid:
This is probably the main factor that hooked me away from the lowveld bush to the mesic grasslands of the Mpumalanga escarpment: The incredibly beautiful flowers! Stumbling upon a brilliant flower, like this Sheathed Sword Lily, Gladiolus eckloniiI, in the rolling grasslands simply lightens up my day. Every time. Gladiolus is a genus with about two hundred and seventy species spread over Europe, the Middle East, Madagascar and Africa but its center of diversity is here in Southern Africa, particularly the Southwestern Cape, with one hundred and sixty six of those species (eleven species on Finsbury so far) occurring. These striking flowers whose sepals and petals are not distinguished from each other (called tepals), making them even more attractive, usually sport multiple flowers, in different stages of development, on an erect spike. The male parts of the individual flowers develop before the female parts in that flower and these individual flowers develop from the bottom of the spike upwards over a set time (this is called Protandry, refer the second article, featuring the plump caterpillar of a Hawkmoth, of my blog of Christmas 2021). This decreases the chances of self-pollination because the flower's chosen pollinators have a hereditary behavioral influence that makes them visit the bottom flowers on a spike first, before moving to the next flower above on the spike, searching for nectar. This insures that the bottom flower gets pollen deposited on it from the previous plant visited before the pollinator gathers the pollen from this plant's first flower and moves upward to the next flower on the spike that has not yet developed the female part. So the pollen now collected from the bottom flower, is not deposited on the female part of the flower above it because it has not developed yet. Instead the pollinator collects more pollen from the higher flowers (because the male parts have developed already) that it will carry to the following plant. Phew! Harder to explain then I thought. But, if you understood my rather shaky explanation, you'll see yet another example of the intricate and co-evolved relationships between flowering plants and their chosen pollinators.
I took this photo of a small family group of Rock Hyrax, Procavia capensis, in the bottleneck that leads into Hidden Valley about a kilometer east of the Kliprots road. Most of the Hyrax colonies I have seen on the estate are small family groups like this one except for a large colony in the cliffs far behind and above Kliprots Creek (unit 24), and a large colony in the fallen rocks below the cliffs of Potato Seed Production, high above Rainbow Rivers (unit 17). They live in a harem system so the smaller family groups, like this one, consist of one large, dominant male (right of center), with one to seven related females and their offspring. The larger colonies consist of many of these harems, all living together but having limited contact with other harem groups in the colony.
These pudgy, serious-looking animals belong to the Paenungulata clade in the Afrotheria superorder of mammals and were previously thought to be the closest relative to the elephant. They certainly are from the paenungulata clade, together with the elephants but more recent research has placed the Dugongs and Manatees (order Sirenia) as closest relative to elephants (order Proboscidea). They live in small territories, defended by the male, of less than a half a hectare, along cliff faces and fallen boulders. These territories are advertised with conveniently spaced latrines where all members defecate and by vocalisations from the dominant male.
As herbivores, they have multi-chambered stomachs like ruminants, but they do not chew the cud so are not ruminants, to help them digest the hardy vegetation that is associated with this habitat. Other adaptions include four-toed front, flat-footed (plantigrade) feet and rear, three-toed feet that stand almost on tippy toes. The underside of the feet are made up of large, black pads that are constantly moistened by sweat glands. These adaptions help it move around and over the rocks with surprising agility.
The breeding season starts around now and the male becomes more grumpy and vocal while his testicles grow to twenty times their normal weight. He will mate with all the adult females that are ready to conceive in his harem and they will carry the litter, of around three pups, for a gestation of an astounding seven months! The extremely well-developed young are born in spring and are able to jump from rock to rock within a few days. Although they are weaned by three months, they already begin to eat vegetation before the first week of their lives are over.
Their rocky, exposed habitat is subjected to extreme temperatures and so much of the ninety-five percent of time they spend resting involves thermoregulation activities, like sunning themselves to heat up or retreating into crevices in rocks to cool down. Very much like cold-blooded reptiles. They are inactive during cold, wet days and sometimes active on warm moonlit nights and while they forage, they always have a few sentinels placed in strategic lookouts points to warn them of impending danger. Although they are the staple diet of Verreaux's Eagles, Leopards, Caracals and pythons are probably their worst enemies. They do, however, enjoy an average life expectancy of ten years in the wild.
I can't help featuring photos of these lovely, photogenic little spiders. Once again, a photo of a Crab spider, Thomisus sp.(see blogs of March 2018 and May 2020), but this time with its prey, a large, hairy fly of sorts. The spider sits atop an open flower, in this case an Umbrella Everlasting, and slowly, like a chameleon, changes to the same colour as the flower, becoming invisible to the unsuspecting nectar or pollen seeking insect that may come visit. As the insect alights on the flower, the spider grabs it with its powerful, over-sized forelegs and quickly bites it and injects a fast-acting venom that subdues the prey before it can struggle free. This Crab spider then moved to the underside of the flower so that it could lap up the juices of its prey without being seen...
Oooh! Death lurks in the grass! It's definitely not typical to find a Brown Button spider, Latrodectus geometricus, walking on the grass because they are rather strictly web-bound. The only reason this one is, is because I moved it there from the typically untidy nest in the dark recesses of my patio bench and table while I was cleaning. They are normally a more brown colour with slight chevron markings on the sides of the abdomen and with the banding on the legs more pronounced. But this is a very old female and so, she the Brown Widow, is almost pitch black. I did get to see the give-away brilliant red and orange hour-glass shape on the dorsal part of her abdomen (as opposed to the hour-glass pattern on the ventral part in the Black Widow) but she was not prepared to show me for the photo. They normally reside in an untidy, three dimensional web in dark, still places which can be identified by the pale, spiky egg sacks (smooth in the Black Widow), about eight millimeters in diameter, entangled within. Because of their secretive and sedentary behavior, bites are almost never heard of. Thankfully because the venom is extremely potent and, although the same potency for the Black and the Brown Widow, the Black Widow is capable of injecting larger amounts than her Brown cousin. It is a neurotoxin that, if enough is injected, can cause a dangerous condition called lactrodectism, where the victim will experience intense pain around the bite; prickling skin and goosebumps; then hypertension (and a bunch of other hypers!); nausea and vomiting; abdominal pain and more. If left untreated, symptoms should subside by three days although fatigue, insomnia and general weakness may persist for months even. Scary. The Black Widow, L mactans, was always believed to be the most dangerous Southern African spider with this, the Brown Widow, a close second. But it is now believed that the Six-eyed Crab spider, Sicarius hahnii, is potentially the most dangerous spider in Southern Africa but there has never been a record of a bite on a human. If tests on rabbits are anything to go by, the cytotoxicity of the venom causes severe necrosis and the Hemotoxic element causes massive internal hemorrhaging, causing a rapid death! And I had the honour of seeing a whole bunch of these really rarely seen spiders, on my own, in a sandy cave, high up on the Mikberg mountain in the Damaraland desert, in Namibia, at the close of the last century. I knew that they were highly venomous and rare so I relished the experience. A pleasant memory. I took a bunch of photographs that I developed into slides which I must try and dig up.
Grasslands began to evolve in the middle to late Cretaceous between seventy and sixty million years ago but they only started to dominate as a biome a mere six million or so years ago. They have had a huge influence in natural ecosystems and are the main reason for the speciation of large grazers like antelope and deer in the last twenty five million years. In South Africa, the grassland biome, which covers almost twenty five percent of the land area, is the second largest, after the savanna biome, but is the biome under the most pressure from human activities. Thirty percent of the grassland biome is transformed irreversibly and another thirty percent is partially degraded and poorly managed. The remaining forty percent is in a relatively pristine state but is highly fragmented and only slightly over two percent of this is formally protected.
Probably the biggest benefit high altitude grasslands play in environmental ecology is as water catchment areas. This is why we are part of the Mount Anderson Water Catchment Reserve. Let me explain why: Grasses are designed to be crowded together with other grasses and that is why the have lanceolate leaves that point upwards, a design that allows them to receive sufficient sunlight for photosynthesis in their crowded conditions. Another significant feature shared by grasses is that their leaves' growth point is at the base of the leaf or stem instead of on the apex of a stem (research intercalary meristems). So, if you cut a grass's leaf blade in half, it just continues growing from the base (like our hair) whereas if you cut a woody plant's leaf in half, the leaf dies. This means that grasses can flourish in extremely crowded conditions and also survive when grazed, mowed and burned. Woody plants cannot.
These massive tracts of grasslands in high rainfall areas (like ours) act like a sponge and promote rainfall infiltration. In fact, in 2003, Reyer's and Tosh proclaimed that, on the plateau, "rainfall infiltration in grasslands is solely responsible for providing water to the entire Gauteng province". But the efficiency of this sponge is directly related to the condition of these grasslands. The grasslands' condition can be assessed by it's basal cover. The spaces between each plant (the bare ground) are measured by grassland ecologists and this measurement will give you the basal cover of that particular area. A poor basal cover is when there are large spaces between plants and a good basal cover will be when there are only small spaces between plants, allowing less run-off during the rains and thus, more absorption. Also, the design of the grass plant guides the water, during rain, straight to the bed of the plant, which actually forces the water into the ground instead of allowing it to run away. (this is very noticeable when you water your lawn, there is virtually no runoff until the ground is saturated).
Now, grasslands have been burning regularly since they evolved into huge grasslands, long before humans had any influence on them. This is easy to understand when one looks at the massive species count of other plants with underground storage devices (USOs) like bulbs and geoxylic suffrutices (underground trees) that coexist with the grasses in grasslands that have evolved those USOs as a defense against fires. These non-grass plants have a herbaceous growth form that can grow when conditions are good and can be destroyed by fire while not damaging the plant which is protected underground, just like grasses.
Before human interference, fires were mostly started by lightning strikes but, unless it was during a dry thunder storm, which are not rare on the escarpment and plateau in South Africa, only a small area would burn before the rain extinguished it. But if it were started during a dry thunderstorm, even when the grasslands are green and moist, it would burn until either the fuel load was too small, or until the following rains fell. The roads and fire breaks that we construct, and our actions, stop these fires and so if they were not in the equation, a relatively rare natural fire would burn massive tracts of land before it was extinguished. Much more rarely, in the dry season, fires may have started by falling rocks causing sparks (there is a lot of pyrite in our grasslands) which could ignite the dry grass leaves, burning massive tracts of grasslands. When I talk about fuel load, I refer to moribund. During our cold winters, grasses pull their nutrients into their roots for storage until the next growing season and the grasses leaves dry out and die, unlike woody plants that drop their dead leaves, grasses' dead leaves remain attached to the plant and build up over successive growing seasons. The following season, new grass leaves emerge amongst the old dead leaves. If the grass plant is not burned every few years (three to four seasons in our area), the build up of these dead leaves, which are referred to as moribund, begins to smother the grassplant's neighbours by blocking out the sun for them and, ultimately, smothers itself. Once its neighbours have died, there will be a shaded patch of bare ground where they used to be and this is a nice habitat for woody plants' seeds to germinate, and so they will.
As early as the nineteen fifties, ecologists realised that "mesic grasslands do not exist in equilibrium with their climate and could return to a forest state if fire was excluded from the system" (Acocks 1953) Now, as mentioned above, woody plants (dicotyledons) are a very important component of natural grasslands and will often outnumber, in a number of different species that are designed to co-exist with grasses, the grassplants in a healthy grassland but these species do not grow taller and shade the grasses. The encroachers, the taller woody plants that need to be controlled, are also a natural component of the grasslands but they should never dominate, and would never in the presence of fires. In a situation described at the end of the previous paragraph where patches of shaded, bare ground form, these encroachers will quickly grow taller than the grass plant (the leaves not inflorescence) and soon succeed in smothering those grass plants that smothered their neighbours originally! These woody plants will then dominate and the problem with that is that these woody plants usually have a main stem, or are multi-stemmed, which supports a canopy of leaves. So although it appears like the ground is fully covered by plant-life, there are large spaces of bare ground between each plant's stem/s (poor basal cover) and then when it rains, the water rushes down the slopes on the mostly bare ground, where it will erode the topsoil away and instead of being absorbed into the ground, will run into the rivers and away. Refer to the sixth article in my blog "Early Spring Time" (posted on 28 Sep 2021) for more on this.
Our mountains are mostly made up of porous sedimentary rock and so each mountain is an aquifer. When water is absorbed into the rock, it fills up and, because the water cannot run freely out of the rock due to friction against the rock granules, the rock acts as a storage unit (an aquifer) that slowly releases the water, by gravitational force, out of natural cracks and seeps (springs) which feed our rivers throughout the year, even during the dry season. So if the grasslands were compromised, there would be no absorption and so flash floods during the rainy season, and drought during the dry season with no flowing rivers. Devastating!
In the last few years, since I have been in charge of burning here on the estate, I have concentrated on removing the woody plants with hot block burns to try and get the grasslands in the correct condition for PMBs. PMBs are generally cool fires and so, if I cool burn an area that is being dominated by woody plants, the woody plants will not be killed and the fire would only remove the moribund which will be slightly beneficial to the woody plants and they will even increase, exacerbating the problem even further.
Anyway, this year is the first year that I have executed proper PMBs. Meaning that I executed them on my own with no staff and only lit the fire at one or a few ignition spots (as in a lightning fire). I burned three small PMBs ( forty to sixty hectares each) in January which were extinguished on the same night by rainfall; a fifty hectare one around the rehabilitation area above and west of Cochy-Y-bunddhu (unit 1) and a sixty hectare one east, west and south of Pebble Creek (unit 25) in mid February which were also extinguished by evening rainfall (very good imitations of natural lightning fires); and then this two hundred and fifty hectare PMB, featured here, that burned for two-and-a-half days before I went up and extinguished it, easily by myself (the benefits of PMBs compared to block burns regarding staff and resources are obvious).
I have gone up and inspected the burned areas from January and can already see areas where brand new grass plants have germinated in the open areas between the older established grass plants, effectively decreasing the basal area which will increase rainwater absorption and reduce sheetwash erosion in the following seasons.
This is as simple an explanation that I can conjure and the subject is a lot more complex but I hope it helps explain what I am doing to transform Finsbury grasslands into optimum high altitude grasslands. Besides the obvious benefits for biodiversity and the ecology of our grasslands, these activities will ultimately reduce topsoil run-off which will reduce silting up of our weirs, reduce resources and staff normally required to execute blockburns and firebreaks, and eliminate the unsightly firebreaks that used to mar the otherwise beautiful montane grasslands in which the estate nestles. If you are interested in this and get a chance while you are here, let me take you on a walk into the grasslands where I can explain this more practically...
So long for now. Enjoy your autumn :)
