Saturday, 29 November 2014

Ethiopian alpines 2: the Sanetti Plateau

The dramatic profile of Lobelia rhynchopetalum: so unexpected in a high alpine environment.
The high point, in every way, of the trip to Ethiopia, was the day we had in the Bale Mountains National Park; it was my third time there, but the first with really good weather. The previous trips had been a month or so earlier and the rains hadn't quite cleared southwards.

The Bale Mountains are a large massif rising south of the Rift Valley, the largest of several mountainous areas there, and an extremely important area for biodiversity in all classes of organisms. Much of the massif is nominally protected by a National Park, but encroachment is a problem and there is continuous forest clearance on the flanks of the mountains. Nevertheless, the park has been instrumental in preserving a large area of habitat that would otherwise have been lost, and under its protection reasonably healthy populations of several large mammals remain.

The centre of the park, the high altitude Sanetti Plateau, the largest contiguous tract of afroalpine habitat,  is easily reached from the town of Goba to the north of the massif - a dirt road leads up and over the top to settlements on the other side. It's used by a surprising number of buses and lorries, and to judger by the great ruts inm the road many obviously have significant difficulties ion the wet season - as we did in 2007 when trying to get around in a minibus. With a 4X4 the road presents no problems when dry.

Looking toward the northern edge of the Bale mountains: little tarns are a feature of the Sanetti Plateau.
The ascent is quite rapid, from about 2700 m at Goba, to treeline at 3520 m, and the lip of the plateau at 3800 m: much of the Sanetti Plateau is at or slightly above 4000 m, so there is a risk of altitude sickness. Fortunately none of us was affected beyond a tinge of headache and slight breathlessness.

Without doubt the botanical highlight of Sanetti is the largest of all of the giant lobelias, L. rhynchopetalum. This gigantic plant, standing 4-6 m tall in flower, is endemic to the highlands of Ethiopia both north and south of the Rift Valley - none of the other species come close to it in stature. We seem to have hit a really good flowering year for it, to judge by the number of spikes to be seen, but most had now finished and were maturing their seeds. In a few a ring of light blue flowers could be seen on the spike, but in all cases too far up to be accessible for a picture.

Mass-flowering of giant lobelias: the big rosettes will flower in a year or two's time.

Seedlings start off as small, stemless rosettes.
  
The rosette develops over a number of years, getting larger and increasingly elevated on a stout stem, taking about 12 years to reach flowering size. The inflorescence in the background still has fresh flowers in its upper portion, but the leaves are already senescing.
After seeding, the plant dies and collapses, leaving a heap of rather attractive 'skeleton'. 

The giant and the dwarf: the tiny spangles of blue just visible in the foreground are the flowers of the minute, prostrate Lobelia erlangeriana - there could not be a more striking disparity in the sizes of plants in the same genus.

Lobelia erlangeriana - a very pretty little plant.

A tight tuft of Swertia lugardae. Swertia replaces Gentiana on the African mountains.
A widely-distributed plant, Erigeron alpinus is common in the European mountains, and occurs through Ethiopia to Mt Kenya.

The very beautiful mat-forming Helichrysum gofense - white capitula above silvery leaves. A common plant on the Sanetti Plateau, but it is endemic to high altitudes in Ethiopia south of the Rift Valley.

An Augur Buzzard, Buteo augur, on a roadside boulder. The grey vegetation in the background is the classic Afroalpine Helichrysum moorland, here dominated by H. citrispinum and H. splendidum.  The subtly spicy scent of Helichrysum moorland is one of my favourites, now a very rare treat. The hill to the left, with a radio station on top is Tullu Demtu, the highest peak of Bale at 4377 m. We trudged to its top in foul weather in 2007.

A bush of Helichrysum citrispinum covered in flowers.

As its name suggests, Helichrysum formosissimum is the most beautiful of  the Afroalpine species, though it grows just over the lip of the plateau, not in the exposed upper places.

The Sanetti Plateau is no place for murophobics: it has an extraordinarily high density of rodents, and mice and grass-rats can be seen scuttling about all over the place. But the most interesting of all is the Giant Mole Rat Tachyoryctes macrocephalus, another endemic, that hardly ever ventures away from its burrows and the grassy hills that they form, eating grasses and Alchemilla rhizomes. Their eyes are placed very high on their heads, enabling them to sit in their burrow-mouth and keep a look out for predators...

of which the Ethiopian Wolf is the most notable. Half of the extant population (somewhere around 400 individuals) of this beautiful animal occurs in the Bale Mountains - we saw 5 on this occasion - but they are threatened by habitat loss and from diseases caught from domestic dogs. They are specialist rodent hunters, with a long muzzle for nabbing them from their holes.

While writing this entry I realised that it marks the fifth anniversary of this diary, which started with a post about Kenya on 27 November 2009, a pleasing African symmetry.

4 comments:

  1. What an amazing monocarpic plant!
    6meters high is huge!
    You say about 12 years for the plant to develop the rosette. I imagine that amazing spike grows up in one year?

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  2. My cousin and I are going to try grow a few seeds. I live at 2,000 feet and was wondering if the plant will realize the difference.

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  3. thanks for your share, your article very nice

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