East African montane moorlands
The East African montane moorlands is a relatively small alpine ecoregion in eastern Africa. The habitat is virtually treeless, since it occupies a zone chiefly above the treeline. This ecoregion, classified as an element of the montane grasslands and scrublands biome, has a land area measuring only about 1300 square miles. The ecoregion, lying at the upper zones of ancient volcanoes, exhibits low species richness of higher level faunal organisms, but manifests moderate plant and animal endemism, including support of certain extremophiles. There is particularly high endemism among amphibians and small mammals of the ecoregion. Many of the plant species that occur in the ecoregion have adapted interesting morphological features to allow survival in the extreme cold here.
The upper elevations of the ecoregion have persistent glacial cover. Although some of the ecoregion (e.g. Mount Kilamanjaro) has experienced glacial retreat over the last century, that ice cover should be considered time variant over the most recent millennia. Moreover, the recent glacial reduction is viewed to be due primarily to deforestation on lower mountain slopes, which phenomena has led to reduced upslope moisture flow from lessening of forest evapo-transpiration. Soils in the ecoregion are generally acidic, partially explaining the low flora species richness.
Contents
Location
The East African montane moorlands ecoregion is comprised of five disjunctive spatial elements in northern Tanzania, western Kenya and eastern Uganda. Specific locations of the ecoregion include the alpine portions of Mount Kilamanjaro in Tanzania; Mount Meru in Tanzania; Mount Kenya in west central Kenya; Mount Elgon on the Uganda Kenya border.
Climate
Owing to the equatorial position of this ecoregion, there is little difference in temperature throughout the annual cycle. With an minimum of large plants, solar insolation is generally high year around and throughout the day. Virtually every night is accompanied by frost levels, due to the altitude of the ecoregion.
The airflow is mostly driven by fronts arriving from the Indian Ocean, except in January and February when a pattern of winds arriving from the northwest is dominant.
Flora biodiversity
There are a number of endemic plant groups within the ecoregion, likely driven by the extreme isolation of these alpine patches. The giant groundsels are one prominent group of flowering plant species present; this unusual plant group achieves tree-like stature with some unusual methods of cold weather adaptation, even though they are members of the herbaceous family Asteraceae.
Certain giant lobelias occur in the East African montane moorlands. For example, Lobelia deckenii, found on Mount Kenya is characterised by small stores of water retained in its basal rosettes; although this retained water freezes each night, the frozen water protects the apical meristem held in a rather dense central leaf bud. If this reservoir were to be drained, the temperature of the inner meristem would fall below freezing, which event generally does not happen since the fluid or its ice form is left intact owing to the rosette geometry.
Faunal biodiversity
There are a total of 208 vertebrate species that have been recorded in the East African montane moorlands. While this implies relatively low faunal species richness, the harsh climate, lack of forest cover and relative isolation generate circumstances for important instances of faunal endemism.
For example the Kilimanjaro Stream Frog (Strongylopus kilimanjaro) is recorded only in a narrow alpine range on the middle slopes of Mount Kilimanjaro within the East African montane moorlands. The Kenya River frog (Phrynobatrachus keniensis) is endemic to the Kenyan portion of the ecoregion. The Kinangop River Frog (Phrynobatrachus kinangopensis) is endemic to the Kenyan portion of the ecoregion; in particular it is found only in the Mount Kenya and Aberdare National Parks at elevations around 3000 metres.
The Marsabit Clawed Frog (Xenopus borealis) is a near endemic anuran, which is also found in the upper elevations of the adjacent East African montane forests ecoregion. Another near endemic amphibian is the Molo Frog (Amietia wittei), which is found only in the Kenyan central highlands and northern Tanzania in the East African montane moorlands and slightly lower in elevation in the East African montane forests. The near endemic Mountain Reed Frog (Hyperolius montanus) is found only in the Kenyan highlands of the ecoregion and also in the adjacent East African montane forests ecoregion. The Tigoni Reed Frog (Hyperolius cystocandicans) is a Vulnerable near endemic, found only in Kenya in this ecoregion and the adjacent East African montane forests.
Other amphibians present in the East African montane moorlands ecoregion include the Subharan Toad (Amietophrynus xeros), Cape River Frog (Amietia fuscigula), Senegal Running Frog (Kassina senegalensis), Common Reed Frog (Hyperolius viridiflavus), and Keith's Toad (Amietophrynus kerinyagae).
There are a number of endemic small mammals to the East African montane moorlands. One endemic mammal to the ecoregion is the Mount Kenya Mole Shrew (Surdisorex polulus), which is found only at the higher elevations of Mount Kenya; moreover, this rodent is classified as a Vulnerable species. Another endemic mammal is the Aberdare Mole Shrew (Surdisorex norae), which is known only to the higher elevations of the Aberdare Mountain Range in Kenya. The King Mole Rat (Tachyoryctes rex) is another endemic rodent that is known only to the higher elevations of Mount Kenya within the ecoregion. The Vulnerable East African Highland Shrew (Crocidura allex) is a near endemic to the ecoregion, that is also found in upper elevation portions of the adjacent East African montane forests ecoregion. Another imputed endemic mammal is Peter's Musk Shrew (Crocidura gracilipes), whose location is generally assigned to this ecoregion based upon the sole, yet imprecise, recording of the holotype.
Other notable mammals found in this ecoregion are the Endangered Painted Hunting Dog (Lycaon pictus), African Civet (Civettictus civetta), the Near Threatened Leopard (Panthera pardus), the Near Threatened, but widespread, Straw-coloured Fruit Bat (Eidolon helvum), African Clawless Otter (Aonyx capensis), Bushpig (Potamochoerus larvatus), Common Rock Hyrax (Procavia capensis), Black-tipped Mongoose (Galerella sanguinea), Common Warthog (Phacochoerus africanus), Small-spotted Genet (Genetta genetta), the widespread Bohor Reedbuck (Redunca redunca), the widespread Angolan Free-tailed Bat (Mops condylurus), the Banded Mongoose (Mungos mungo), Zorilla (Ictonyx striatus), and the near endemic Audacious Mole Rat (Tachoryctes audax).
The Mount Kenya Side-striped Chameleon (Triceros schubotzi) is an endemic reptile found in the ecoregion; a second member of this genus, Triceros sternfeldi, is also endemic to the East African montane moorlands. The High-casqued Chameleon (Triceros hoehnelii) is a near endemic reptile to the East African montane moorlands; it is also found in higher elevations of the adjacent East African montane forests ecoregion. The Kenya Montane Viper (Montatheris hindii) is a near endemic that occurs only in the Kenyan part of the ecoregion and at slightly lower elevations in parts of the Kenyan East African montane moorlands. Special status reptiles found in the ecoregion include the Vulnerable Alpine Meadow Lizard (Adolfus alleni), a near endemic found only at high altitudes (above 2700 metres) on Mount Elgon, Mount Kenya, Cheragani Hills and the Aberdare Mountains.
Ecological threats
While the ecoregion is protected from much human intrusion due to its high elevation and severe climate, there are threats to the ecosystem stability due to changes in moisture and glaciation of some of the elements. For example, atop Mount Kilimanjaro, there is a century long glacial retreat documented by Pepin et al. (2010). However, this reduction in glacial extent has been traced to deforestation by native peoples on the lower slopes of Kilimanjaro; this massive loss of forest has produced a dramatic decline of upslope driven atmospheric moisture, due to the lower evapotranspiration rates where deforestation has been occurring.
Ecoregion status
The ecoregion is classified as relatively stable and intact; this outcome chiefly derives from the limited presence of man in this harsh and cold climate. The East African montane moorlands is given the designation as a Global 200 ecoregion by the World Wildlife Fund, meaning that this ecoregion is considered among the world's most 200 outstanding and representative ecoregions of biodiversity.
Justification of ecoregion delineation
This ecoregion is a well defined disjunctive assembly based upon an altitude niche greater than 3000 metres in elevation in the East African equatorial zone. The ecoregion is well defined as above the treeline, and in a climatic zone that experiences nightly frost. The World Wildlife Fund has designated the ecoregion as AT1005. It is classified in the Afrotropical ecoregion category.
References
- C. Michael Hogan. 2013. Strongylopus kilamanjaro. ed. B.Zimkus. African Amphibians http://africanamphibians.myspecies.info/node/2728
- O.Hedberg. 1997. High-Mountain areas of Tropical Africa. Pages 185-197 in F.E. Wielgolaski, editor. Ecosystems of the World 3: Polar and Alpine Tundra. Elsevier, Amsterdam. ISBN: 0444882650
- Eric B.Knox. 2004. Adaptive radiation of African montane plants. In Ulf Dieckmann, Michael Doebeli, Diethard Tautz, Johan A. J. Metz. Adaptive Speciation. Cambridge University Press. pp. 476. ISBN 0-521-82842-2.
- Eric B.Knox, Jeffrey D. Palmer. 1995. Chloroplast DNA variation and the recent radiation of the giant senecios (Asteraceae) on the tall mountains of eastern Africa. Proceedings of the National Academy of Sciences. 92 (22): 10349–10354.
- N.C.Pepin, W.J.Duane & D.R.Hardy. 2010. The montane circulation on Kilimanjaro, Tanzania and its relevance for the summit ice fields: Comparison of surface mountain climate with equivalent reanalysis parameters. Global and Planetary Change. 74(2), 61-75.
- B.W.Thompson. 1966. The mean annual rainfall of Mount Kenya. Weather 21: 48–49
- Truman P.Young, Mary M.Peacock. 1992. Giant senecios and alpine vegetation of Mount Kenya. Journal of Ecology (British Ecological Society) 80 (1): 141–148.
