1. 3. Study Site
1.3.1. Location
The Mikeno sector (29 ° 21 'E - 29 ° 36' E and 1
° 20 'S - 1 ° 31' S) is part of the southern sector of Virunga
National Park (Mikeno and Nyamulagira), forming the Congolese component of the
Virunga Volcano Range. The Mikeno area is adjacent to and contiguous with the
Parc National des Volcans (Rwanda) and Mgahinga Gorilla National Park
(Uganda).
1.3.2. Climate
Data on the climate of the Mikeno sector are only available
for over 50 years ago. Rainfall surveys taken from 1930 to 1957 using a rain
gauge installed at the top of Mount Karisimbi at 4500 m above the sea level,
showed an average annual rainfall of only 940 mm , but with quite large
variations between years: an annual minimum of 562 mm versus a maximum of 1329
mm, more than double. Coarsely speaking, the Virunga National Park in general
and in particular the Mikeno sector, analysis of temperature (averages, maximum
and minimum) in both low altitude and high mountains, shows that they have
remained stable for several decades (Languy and Merode, 2006).
The IGCP, in its new conservation strategy taking into account
the effects of climate change envisages the installation of a network of
micro-climate stations around the entire Virunga Massif aiming to study how
climate changes at micro-habitat level may affect mountain gorilla
behaviour.
1.3.3. The Virunga National Park, the Mikeno sector and
climate change
Languy and Merode (2006) showed that the geological history of
the Virunga National Park is closely linked to that of the Albertine Rift,
which includes it. The formation of the latter is still ongoing; the two sides
of the rift follow the tectonic plates which separate eastern Africa from the
rest of the continent. Witnesses of this evolution, active Nyiragongo and
Nyamulagira volcanoes are among the most active in the world. This geological
dynamism has had always an evident impact on the history of park's habitats and
plant communities. The succession of the different phases of climate change
through history explains the current species rich biodiversity observed in
Virunga National Parks.
Biodiversity survey of Mwaro corridor, Altitudinal
distribution of the vegetation and assessment of Gorilla food
availability
1.3.4. Vegetation and biological value of the Mikeno
sector
The vegetation of the Mikeno sector is Afromontane. It is,
according to the typical classification, that which grows at different
altitudes on the African continent according to the latitude and local climates
(especially dependent on the importance and frequency of rains). In the Mwaro
ecological corridor, mountain forest begins at about 1800 m above sea level.
Data gathered in the present study will be used to update
information regarding the area's vegetation.
According to Languy and Merode (2006), the range between 1800
and 2800 meters contains a dense humid forest dominated by Ficalhoa
laurifolia and Podocarpus milanjianus, but generally very diverse
and rich in plant species. The trees reach 25 m with usually small leaves. At
the same altitudinal band, recently deforested areas are evident by the
presence of a secondary forest dominated by Neoboutonia macrocalyx.
The bamboo forest is generally between 2300 and 2600 meters on
loose soil rich in humus. This is monospecific vegetation of the species
Sinarundinaria alpina. Bamboos are enormous fast-growing grasses whose
young shoots are eaten by mountain gorillas. Apart from the glades, this type
of forest is not conducive to the development of rich and diversified
undergrowth. Several herbaceous plants including Viola abyssinica
and Clematis sinensis are found in this type of vegetation.
The main vegetation type around 3000 m is the Hagenia
abyssinica dominated forest which is an open forest. At this elevation,
precipitation decreases significantly and the average temperature drops
rapidly.
At higher altitudes, grows a forest of heath, consisting
mainly of the species Philippia johnstonii rising up to 10 m high and
Erica arborea growing on the dry slopes. The ground is typically
covered with a thick layer of moss.
At the upper limit of Hagenia abyssinica and heather
trees (Afro-Alpine floor) towards 3700 meters, appear large clearings. The most
typical species of these elevations are the Lobelia and
Senecio, reaching about 8 m high.
The upper surfaces of Mikeno are steep, contrary to what is
observed on other extinct volcanoes in Virunga massif. The biological value of
the Mikeno sector is mainly linked to its rich and unequaled biodiversity,
compared to other sectors. Central to this diversity is the mountain gorilla,
endemic to this area as far as the DRC is concerned. The preservation of the
mountain gorilla was the very purpose of the creation of the Virunga National
Park, formerly Albert National Park in 1925, as a result of the ideas and
pressures of the naturalist and taxidermist, Carl Akeley. Akeley has stated
with certainty the idea that gorillas in the sector were few, not suspicious or
dangerous and that, consequently, the extinction of this subspecies was
imminent if conservation measures were not taken (Languy and Merode, 2006).
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