Geology Reference
In-Depth Information
gle-Dominant Afromontane Forest of White
(1983) into the deiniion of dry montane forest.
At Mufindi in the southen Uzungwa Mountains,
dry montane forest species occur in small forest
patches on termite mounds in grassland on highly
leached soils with a rainfall of 850
m
per year
(Lovett
&
Gereau, 1990). Edaphic factors thus
appear to determine the lower rainfall limit under
which forest can grow.
Occasionally woodland species such as
Eyth-
ina ayssinca
occur. Late successional stages
include fire resistant rees such as
Agauria salici-
olia
and
My rica saliiolia
which grow in high
alitude grassland or on podzolised soil resuling
from forest clearance. They also occur in late
succession in upper montane and montane forest.
Southen Easten Arc dry montane forest has
edge species such as
Zyherella magalismontana,
Dais cotonifolia, Diospyros whyteana
and
Garcinia
kingaensis
reaching their northen limits.
Other trees in dy upper montane orest
include:
Albizia ummera, Aphloia theomis,
Apodytes dimidiata, Bersama abyssinica, Cassine
aethiopica, Cassipourea malosana, Catha edulis,
Croton marostachyus, Cussonia sp icata, Ekeber,a
capensis, Euclea divinorum, Halleia lucia,
Marga ritaria discoiea, Nuxia congesta, Olea capen-
sis, Olinia rochetiana, Parinai xcelsa, Prunus afi -
cana, Rapanea melanophloeos, Rawsonia lucia,
Schrebera alata, Vp is stolzii, Trich ocadus elliptius.
Trees in lower alitude dry montane forest
include:
Albizia gu mmfera, Bersama abyssinica,
Cssine aethipica, Cola reenwayi, Craibia brevi-
ca uata, Dypetes gerrardii, Manilkara discolor,
Margaitaia discoidea, Ochna holstii, Stychnos
mitis.
Dy montaneorest
Alitude:
>
1500 m. Rainfall: 1000-1200
mm/year.
Syn
onyms: Montane forest belt (Hedberg,
1951). Dry montane orest (CCT/CSA,
1956). Montane forest (White, 1970).
Upland dry evergreen forest (Greenway,
1973). Drier types of undiffereniated
Afromontane forest (White, 1983). Dry
transiional montane forest (White, 1983).
Canopy height: 10-20 m with emergents to 30
m. Basal area: 20 m2ha. Stem sizes:
Few large trees
>
100 cm dbh, most trees
<40 cm dbh. Stem density: 240 stems
>
20 cm dbh/ha.
Dry montane forest as defined here is the most
problemaical of the forest ypes as it is exremely
variable and changes with alitude. Dry orest
rees can have wide alitudinal ranges and extend
into a variey of vegetaion types, for example:
Apodytes dimidiata, Magaritaia discoiea, Parinari
excelsa
and
Rapanea melanophloeos
can occur in
both high alitude and low alitude dry orest. The
classificaion of forest with
Junipeus procera
or
Hagenia abyssinica
also presents a problem. Both
hese species are light demanders;
Juniperus
regenerates following fire (Hall, 1984) and it is
thought that the ire sensiive
Hagenia
may replace
moister forest ypes as a pioneer following fire
(Greenway, 1973). The West Vsambara
}unipeus
forest is clearly disinct from other West Usam-
bara moist forest ypes (Lovett, 1990b), and on
Luhombero in the northen Uzungwa,
Hagenia
occurs as pure stands Q. B. Hall, unpublished
data). However, both species also occur at low
densiies in mixed forest:
Juniperus
in the West
Usambara Shume-Magamba forest and
Hagenia
on Selebu Mountain in the norhen Uzungwa.
Greenway (1973) included forest
ith}unipeus
in
upland dry evergreen forest and put
Hagenia
into
upland evergreen bushlands together with other
degraded or early successional stages of dry mon-
tane forest. The most pracical course is to
include them in dry montane forest when they are
in mixed stands, and qualiy the forest ype when
they are dominant. This would include the Sin-
Up er montane orest
Alitude:
>
1800 m. Rainfall:
>
1200 mm/year.
Synonyms: Montane forest belt (Hedberg,
1951). Bamboo zone (Hedberg, 1951).
Moist montane forest (CCT/CSA,
1956). Higher alitude ypes of
submontane moist forest (hite, 1970).
Wetter low canopy types of montane
forests (White, 1970). Higher alitude
types of upland rain forest (Greenway,
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