UCBG plant collecting trip to Chobe District

Staff from UCBG, together with a group of final year plant taxonomy students, undertook a field trip to the Chobe District (Northern Botswana) from 20 to 25 February 1999. The objectives of the field trip were two-fold; firstly it was to strengthen the students’ collection techniques and augment taxonomic knowledge they had acquired in the classroom; and secondly to have the students help in starting up a collection of the district.

As is usually the case with most collections, specimens in Botswana’s herbaria are mainly from accessible areas along railway lines and main roads. Areas away from these are under-collected and hence underrepresented in our collections. This trip provided an opportunity to collect from areas away from the road.

The journey started on 20 February 1999 at the University of Botswana campus. There is a remarkable change in vegetation as one drives from Gaborone to Kasane. This change is mainly due to a rainfall gradient and probably soil types. Rainfall received per annum increases northwards from 400 mm in the Gaborone area to 700 mm in the Kasane area. One would therefore expect this to have an influence on densities and diversity of plant species. The vegetation is tree savanna for most of the way.

The stretch between Gaborone and Mahalapye (200 km) is the typical Kalahari vegetation, which is dominated by Terminalia sericea, Burkea africana, Peltophorum africanum, and a host of Acacia and Combretum species, such as Acacia tortilis, A. fleckii, A. erioloba, Combretum apiculatum, and C. zeyheri. This is not really exciting for someone who has spent most of his/her lifetime in southern Botswana. About 30 km to the north of Mahalapye is Radisele village. A few kilometres up the road is the first cordon fence at Makoro lands. It was here that life started to be botanically different!

Acacia erioloba

Sitting next to me was a student who comes from the area, and to my delight and surprise, pointed out the window and said to me “Sir, that is the southernmost Mopane along this road in Botswana.” I was delighted because I had learnt something, and surprised because this was the same person who always seemed indifferent in class. I said to myself, “If this guy is this enthusiastic, I must be in for a treat from the other students”, and, indeed, this was to be. Well, it had been a change entering the mopane zone, but the landscape soon became monotonous, because this zone stretches from Radisele to Nata, which is a distance of about 300 to 350 km.

The monotony is broken in the Nata area where stands of the palm, Phoenix reclinata are characteristic, as well as the very strange termite mounds! These are strange in the sense that they lean to the west and their bases are shaped like human testicles (according to an ecology colleague who was with us). The palms in the Nata area are thought to be indicative of—remnants of—a large lake that once occupied the area that included the Makgadikgadi pans. One leaves the predominantly mopane zone at about 100 km north of Nata Village.

From there, it is mixed woodland, consisting of Baikiaea plurijuga, Colophospermum mopane, Burkea africana, Sclerocarya birrea, and Terminalia prunioides. This area, northwards to Kasane, is elephant country. This animal, together with giraffe and duiker, is a common sight in the area. It usually helps to have someone who knows what action to take in case you find an elephant on the road or next to it. I gave the steering wheel to my colleague, together with the students, surrendered my life to God, and hoped for a safe drive for the rest of the journey. After missing a few duikers and slowing down for a couple of elephants, we arrived in the Chobe district at Pandamatenga Village at last.

Chobe contains one of the few true forests and deciduous woodlands within Botswana. The forest vegetation and associated fauna are part of the Zambesian region centred further north. Only in the Chobe section of the country is rainfall sufficient enough to support more or less closed canopy forest. There are five forest reserves in the district: Sibuyu, Kazuma, Kasane, Chobe, and Maikaelelo Forest Reserves.

The dominant species in these reserves are Baikiaea plurijuga (mukusi) and Pterocarpus angolensis (mukwa). The mukusi forests represent the southernmost extension of the natural range of this species, which is geographically restricted to a narrow belt stretching from southern Angola eastwards through southern Zambia and northern Botswana to the west-central parts of Zimbabwe. Mukusi is internationally recognised to be in need of conservation measures, as it has been severely exploited in neighbouring countries.

The woodlands of Chobe are mixed miombo. According to a 1992 survey by the Norwegian Forestry Society, the mixed miombo woodlands in Chobe, in addition to pockets of mukusi-dominated forests, appear to be composed of two, possibly three sub-types:

·         Mixed deciduous woodland dominated by mukwa, Kirkia acuminata, Schinziophyton rautanenii, and Brachystegia boehmii, with mukusi as a subdominant

·         Burkea africana–Terminalia sericea dominated type on shallower and drier soils frequented by fire

·         Mopane dominated type on harder, poorly drained soils, mainly near pans and in the south

The idea was to collect as much as we could on this field trip. The next step would be to make a detailed characterisation of these woodlands—information that is still lacking for sound management strategies to be implemented. Chobe District is thought to harbour one of the largest and densest populations of elephants on the African continent. Elephants exert impacts on the vegetative composition of all the Forest Reserves in Chobe (Senior Wildlife Officer (Kasane), pers. comm.); they occur in all the Forest Reserves during the wet season, and in concentrated numbers in western Chobe and Kasane Forest Reserves during the dry season.

We arrived in Kasane at the Chobe Safari Lodge just after 19h00, unpacked our bags and started taking the day’s dosage of malaria prophylaxis and applying “Peaceful Sleep” (insect repellent) to protect ourselves from malaria. A warm dinner on the terraces overlooking the Chobe river was a delight before we retired to our rooms, some of us passing by the “watering point” to soothe our throats! The following morning (21 February) saw us board a boat, The Fish Eagle, for a cruise on the Chobe River.

The idea was to start the morning by collecting aquatic plants, and those in marshy areas. Aquatics collected included Trapa natans, Nymphaea lotus, Potamogeton thunbergii, and Ceratophyllum demersum. Interestingly, very few plants of Salvinia molesta were seen. This was welcome news because this water fern used to be a problem in the area. No one knew what had happened to decimate the populations of the species.

Plants of the marshy areas included Cyperus papyrus, Phragmites australis, and Miscanthus junceus. I was disappointed not to come across any ferns other than the Salvinia. By the riverbank, we collected Diospyros mespiliformis, Persicaria limbata, Guibourtia coleosperma, Croton megalobotrys, Trichilia emetica, Syzygium cordatum, and Ficus sycomorus, to name a few. It was a pleasant morning, and we went for lunch elated with what we had collected. After pressing the plants, we again went on a boat cruise, this time on The King Fisher, around the disputed Sedudu/Kasikili Island.

The island is found between two channels of the Chobe. The dispute arises from the fact that Botswana considers the main channel and hence the border with Namibia to be the northern channel, while Namibia considers the main channel to be the southern one and hence the border with Botswana. We were not concerned as to whom the island belonged to; we just wanted to have a look at the botanical diversity on the island. We were advised not to disembark in case we got caught in the crossfire.

Therefore, we “botanised” from a distance. All that one could see was water reeds, with a few scattered tree species. A marvel to watch was a group of elephants swimming across the Chobe River from the island back to Chobe National Park. Interestingly, these animals cross the river onto the island to graze during the day and cross back to the park just before sunset. The journey around the island took about 2 hours and we were back at the Lodge to conclude the day by observing the sunset over the Chobe River. It was magical!

The following two days (22 and 23 February) we went terrestrial. We collected and botanised around Kasane Town, and Kazungula and Lesoma villages. We also visited the Lesoma Memorial to pay respect to our lost soldiers. We were able to visit and collect in all the reserves except Maikalelo, which was inaccessible. Our collection also took us into the Chobe National Park along the road to Kachikau and Parakarungu. By the end, fatigue was beginning to set in, so we decided to take a day off (24 February) and crossed the border to Victoria Falls in Zimbabwe.

The sensation of watching the Falls is beyond description of any sort. It is something that needs to be experienced. Even though this was not meant to be a botanical excursion to the Falls, one could not help but observe the good stands of Hyparrhenia sp. along the road, and dense masses of liverworts and mosses in the Falls’ vicinity. It was also nice to come across one of my favourite grasses, Bothriochloa insculpta. In the evening, we were guests at Mowana Safari Lodge, where the main attraction was The Clinton Suite. While the students were busy taking photographs of themselves on the bed that Bill Clinton slept on, I went out and had my last drink in Kasane under the big Adansonia digitata (mowana), after which the lodge is named.

Adansonia digitata

The morning of 25 February saw us packing our luggage and heading back to Gaborone. What was definite in our minds as we left was that this was not going to be our last visit to this beautiful part of the country. Since coming back, I have had visits from a couple of third year students enquiring about plant taxonomy. I hope they choose the subject next academic year for good reasons!

—by Moffat Setshogo

SABONET News 4.1: 74

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