By Peter Høst, Jon C. Lovett,
Charles K. Mabula, Shakim I. Mhagama and Bashir S. Shirima.
8.1.
Abstract.
An assessment of the conservation value of the
Uluguru forests in terms of plants is given and their biogeographical affinity
is briefly discussed. The endemism among plants is very high in the Ulugurus.
There were no data available on the species
composition of montane forest (forest between 1600 and 2400 m) in the Uluguru
South F.R. (Lovett and Pócs 1993). For eight 25 x 25 m plots assessed for woody
plants (with a dbh. of 3 cm or more) at the mistnetting stations at Kimhandu
(1520, 1710, 1940, 2145 and 2520 m) and Lanzi (1710, 1920 and 2110 m) lists are
presented of identified species (47 of 100 species has been identified at
present, comprising the four dominant species in terms of basal area and number
of stems at each station). Structural data of the plots, and diagrams showing
abundance of the dominant species in terms of basal area (BA) and number of
stems are also given. The diversity of each plot is presented as total number
of species, Simpson's and Shannon's indices. Thirteen (28 %) of the species
identified are Eastern Arc endemics, two of these are furthermore Uluguru
endemics.
8.2.
Introduction.
8.2.1.
On the knowledge and affinity of the Uluguru forest flora.
Knowledge. The vegetation and climate of the Uluguru
Mountains have been described by Pócs (1974, 1976a and 1976b) with detailed
information on the lowland Kimboza Forest by Rodgers et al. (1983) and on forest reserves by Lovett and Pócs (1993). The
Ulugurus are part of the Eastern Arc range, which is well known for its high
plant species and generic endemism (Lovett 1993a), and have long been regarded
to be of conservation importance for plants (e.g. Polhill 1968 who mentioned 40
endemic woody plant species from the Ulugurus).
The first botanical collecting is probably that
of W. Goetze who collected there in November 1898. His collections included two
Saintpaulia (African Violet) species
described by Engler as S. goetzeana
and S. pusilla (Baatvik 1993), and
many botanists have collected there since. However, botanical knowledge of the
Ulugurus remains incomplete. Lovett and Pócs (1993) mentioned that there were
not data available on the vegetation of the montane forest (forest between 1600
and 2400 m) of the Uluguru South F.R. (assuming that it is presumably similar
to the Uluguru North montane forest). New taxa are still being found: for
example, Aerisilvaea is a recently
described small tree genus of Euphorbiaceae from Kimboza forest and there is a
still undescribed Cremaspora from
Lupanga peak (Bridson and Verdcourt 1988). Other taxa, such as the giant herb Lobelia morogoroensis, which botanists
have known for many years, have only recently been collected in the appropriate
state to be adequately described. Other plants have been described, but the
type specimens lost. For example, Vepris
mildbraediana was described in 1934 but the type specimen was destroyed in
Berlin during the Second World War. From the original description, it appears to
be a common shrub at higher elevations, but there is little flowering material
in herbaria and a new type specimen still cannot be elected. Only recently have
collections of the shrubby Psychotria
diploneura enabled the nomenclature of Grumilea
diploneura to be updated, the type have been collected in 1894 by Stuhlmann
and subsequently destroyed in Berlin. There are still five other Psychotria taxa collected by Stuhlmann
from the Ulugurus, which are known only from the description, the types having
been lost.
Affinity. As with other Eastern Arc Mountains, the
floristic affinities of the Ulugurus lie primarily with the main African
Guineo-Congolian forests to the west (Lovett 1993a). These affinities are
thought to pre-date the uplift of the central African plateau and suggest that
the Uluguru forests, together with other Eastern Arc and coastal forests, are
remnants of the former Pan-African forest. Examples of western African genera
in the Ulugurus include the forest herb Cincinnobotrys
and the tree Polyceratocarpus. More
remarkable are affinities to Madagascar noted by Leroy (1978). For example, Dionychastrum is related to the
Madagascan Dionycha, and Adenoplusia ulugurensis was once thought
to be endemic to upper montane forest edges in the Ulugurus, but is now known
to be the Madagascan Buddleja axillaris
(Leeuwenberg 1979). There is debate as to whether the affinities pre-date the
split of Madagascar from Africa, or whether they represent long distance
dispersal. Affinities to southern species can be seen in the Eastern Arc
montane forest endemic Schefflera
lukwangulensis, which is related to
S. umbellifera whose northern limits are the southern Udzungwa Mountains
(Lovett and Friis in press).
8.2.2.
Biodiversity value of the Uluguru flora.
The Ulugurus are the wettest of the Eastern Arc
mountains, receiving up to 4000 mm of rain a year, and more than 100 mm of rain
a month in every month of the year has been recorded in Kinole on the eastern
slopes. Although there is little data, the upper slopes are certain to be
perhumid as well, a climatic condition rare in the generally highly seasonal
continent of Africa. Elsewhere in the tropics, rainfall has been correlated
with plant species richness (Gentry 1988). On this basis, the Uluguru Mountains
would be expected to be species rich.
This is indeed the case, with a flora as rich as the other high rainfall
Eastern Arc Mountains and much higher than equivalent areas of forest outside
the Eastern Arc from the Horn of Africa to the Cape.
The Eastern Arc Mountains are thought to have a
history of long-term climatic and geological stability (Lovett 1993a and Lovett
et al. 1988). Long-term stability is
considered to be important for concentrations of restricted range plant taxa in
eastern Africa (Lovett and Friis in press), and so the Uluguru Mountains would
be expected to be rich in endemic plant
species. This is also found to be so, with plant taxa found only in the
Ulugurus in a wide range of life forms from hemi-parasites, epiphytes and
ground herbs to shrubs and trees over the entire elevational range of the
mountains where forest has not been heavily disturbed.
Examples of trees occurring in the Uluguru
mountain forests that are restricted to the Eastern Arc mountains are: Allanblackia stuhlmannii, Cephalosphaera usambarensis and Polyceratocarpus scheffleri. Other
Uluguru trees are only found in the southern Eastern Arc, such as Allanblackia ulugurensis, and some are
known only from the Ulugurus such as Pittosporum
goetzei, which is found in upper montane forest and forest patches on the
Lukwangule Plateau and the newly described Aerisilvaea
from Kimboza.
The Ulugurus are especially rich in endemic
herbs. In the Gesneriaceae, the genus Linnaeopsis
Engl. has 3-4 species only known from the Ulugurus. Three Saintpaulia species are found in the Ulugurus, S. goetzeana, S. pusilla
and S. inconspicua. The first two are
also found in the Nguru Mountains (with S.
pusilla also in the Ukagurus), but the latter is only known from the
Ulugurus. This can be contrasted with the 15 species known from the Usambara
area. In the Balsaminaceae, of the 69 native East African species, 19 are known
from the Ulugurus, and of these 13 are Uluguru (including Kimboza) endemics
(Grey-Wilson 1980 and 1982). All 19 are in the genus Impatiens[1].
The high rainfall and frequent mist and cloud
cover of the Uluguru Mountains is reflected by a rich epiphytic Orchidaceae
flora (Cribb 1984 and 1989), with many endemic species. For example, the genus Bulbophyllum has one Uluguru endemic and
one near endemic (Ulugurus and Udzungwas), Polystachya
has three Uluguru endemics and three near endemics (also on adjacent
mountains), Stolzia has five Uluguru
endemics, Diaphananthe has one
Uluguru endemic and one near endemic and Margelliantha
with three East African species has one Uluguru endemic and one near endemic.
Of ferns, the Uluguru Mountains hold 223 out of
at least 321 forest species known for the whole Eastern Arc but only three
species are endemic (R. Shippers in litt.
1994 to J. Lovett). Mosses comprise no less than 490 species, of which 10 are
endemic, including the endemic genus Pseudotimmiella
(T. Pócs in litt. 1992 to N.
Burgess).
Uluguru endemic or near-endemic genera are from
a variety of families and occur throughout the elevational range of the
forests, at natural forest edges and high elevation grasslands. Linnaeopsis, the Gesneriad already
mentioned, occurs in montane forests. Aerisilvaea
(Euphorbiaceae) is a shrubby tree in lowland forest at Kimboza. Dionychastrum (Melastomataceae) is a
small shrub at the upper montane forest edge. Pseudonesohedyotis (Rubiaceae) is a montane and upper montane
forest small shrub. Rhipidiantha
(Rubiaceae) is a montane forest shrub. Near endemic genera, include Neobenthamia (Orchidaceae), an Uluguru and
Nguru forest edge herb and Urogentias
(Gentianaceae), an Uluguru and Nguru high elevation grassland herb.
8.2.3.
The botanical fieldwork carried out on this survey (confer Table
2.1).
Eight plots at five different altitudes were
assessed at Kimhandu and Lanzi by PH, SIM, CKM and BSS with help also from
local village elders. Plots were objectively positioned adjacent to the bird
net sites at the stations Kimhandu 1-5 and Lanzi 1-3. Each plot (demarcated
with string) was 25 x 25 m (625 m2) and all stems with a dbh
(diameter in breast height) of 3 cm or more were measured (dbh, height and spread
in the longitudinal axis) and identified (shrubs, trees, tree ferns, pachycaul
herbs and lianas). Lists are presented in this report of identified species,
structural data of the plots, and of the dominant species in terms of basal
area (BA) and number of stems. The aim of assessing the plots was to provide a
standardised description of the forest structure and tree diversity for a
representative site within each ornithological study area (in this report we
do, however, not go into any comparison between birds and botany) and to
provide biodiversity and structural data on the little known Uluguru South F.R.
for a large-scaled study of the Eastern Arc Mountains.
Specimens from Kimhandu and Lanzi were
identified at the Botanical Museum of Copenhagen during spring 1994 by PH with
help from JCL. The structural data have been computerised into a database at
BMUC that holds structural data from plots in a variety of Eastern Arc and
coastal forests in Tanzania. Due to a difficult time budget and problems with final
identification of many of the specimens (comparison with Kew specimens
necessary for some of them), the identification process had to be terminated
when only 47 of the c. 100 species had been identified; these were the dominant
species for all stations. Below is listed some of the data to provide
preliminary data on biodiversity value and to give an impression of the
vegetation and the kind of data collected.
Plots were assessed also at the three stations
visited at Tegetero by CKM, SIM and BSS (PH did not visit Tegetero). The
specimens have been identified at the TAFORI herbarium in Lushoto by CKM.
Species lists and structural data are presented in Mabula et al. (1994). Three plots were assessed in Kimboza F.R. by JCL on
a visit in November. These will be described in detail elsewhere.
Ethnobotanical data were collected on local
peoples use of plants for medicine, tools, householding etc. by CKM, SIM and
BSS at Kimhandu, Lanzi and Tegetero. These data are presented in Mabula et al. (1994) with a brief summary in
section 9 of this report.
Plot data similar to those collected on this
survey exist from earlier fieldwork in the Ulugurus (and other Eastern Arc and
coastal forests) by JCL. More details on diversity values (including full
species lists) will be published in a separate paper on the Uluguru vegetation.
8.3.
Methods used on this survey.
The method used to assess the plots was adopted
from Lovett (1993b). The plots were 25 m x 25 m squares (area 0.0625 ha)
demarcated with string. They were positioned adjacent to the bird net sites.
The plots were laid out by first establishing a 25 m line on a compass bearing,
divided into two 12.5 m lengths. From the 12.5 m mark a 12.5 m length was
placed on each side of a compass bearing at right angles to the central line.
Finally, the outside edges of the plot were connected with straight strings.
The plots were laid out in this way to ensure that the area is 625 m2
irrespective of topographic variation. All trees, shrubs, tree ferns, pachycaul
herbs and lianas with a dbh (diameter at breast height) of greater than or
equal to 3 cm (or equivalent if fallen) were identified or collected, and their
dbh, distribution along the longitudinal axis of the plot, and height were
measured. It should be mentioned that bamboos were not included (bamboos form a
prominent part of the forest structure e.g. in the elfin forest at Kimhandu-5
[2520 m]).
8.4.
Results of plots assessed at Kimhandu and Lanzi (confer Tables 8.1-3
and Figures
8.1-23).
A total number of c. 100 woody species with a
dbh of more than 3 cm were found at the plots at Kimhandu and Lanzi. Of these, 47
species have been identified (Table 8.1; Eastern Arc endemics are assigned with
an asterisk in front of the species name. Uluguru endemics are assigned with
two asterisks.).
The information has also been analysed in terms
of the number and sizes of the specimens at the various stations (Table 8.2)
and diversity indices has been calculated for the plots (Table 8.3). Figures
8.1-8.8 shows the basal area dominant species for the eight stations. Figures
8.9-8.16 shows the dominant species in terms of number of stems for the eight
stations. Figure 8.17 shows the total basal area for the eight plots, Figure
8.18 the number of stems for the eight plots. For selected species (Camphor Ocotea usambarensis, Allanblackia ulugurensis and Treeferns)
basal area and number of stems are shown for the eight plots in Figures
8.19-8.23.
8.5.
Discussion of results from Kimhandu and Lanzi.
Due to the small plot areas the total number of
species of trees and shrubs found at the plots (Table 8.1 and Appendix 8.1) is not an approximation
to the total number occurring in the study areas and also the
densities calculated for the species suffer from the small sample size. This is illustrated by
the distribution of Ocotea usambarensis
Engl. and Allanblackia ulugurensis
Engl. which occur throughout the altitudinal range but are not evenly
represented in the plots. They are large and occur in low numbers (these
or other species may furthermore have a lumpy distribution) and could be missed if
the plot size is too small. To get a more true impression of total
species numbers and densities the plot size should probably have been at
least 0.25 ha per station as recommended in Newberry et al. (1992) or more
plots should have been assessed at each of the stations.
A very high proportion (13/47 = 28 %) of the
identified taxa are Eastern Arc endemics, with some (Pittosporum goetzei and Rhipidantha
chlorantha) also being endemic to the Ulugurus. One of the Eastern Arc
endemics, Allanblackia uluguruensis, occurs in good densities. There is
so much difference in the proportion of specimens identified for the various
stations that it is not possible to conclude anything from the variation in
number of endemics listed for the single stations. For the conservation of the
Kimhandu area it is of interest that seven Eastern Arc endemics have been
identified from the lowest plot.
The valuable timber species Camphor Ocotea usambarensis was scored
on plots at
Kimhandu-4 (2145 m), and at all Lanzi stations, and occured at good densities
locally. Tree ferns are very common at the stations, possibly due to the
humid climate (see figures).
Further comments are given in Appendix 8.1.
8.6. References.
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(Gesneriaceae) 100 years: History, taxonomy, ecology, distribution and
conservation. Fragmenta Floristica et
Geobotanica (suppl.) 2: 97-112.
Bridson, D. and B.
Verdcourt 1988. Rubiaceae (Part 2). In Polhill, R.M. (ed.). Flora of tropical East Africa.
Rotterdam: A.A. Balkema.
Cribb, P. 1984. Orchidaceae (Part 2). In Polhill, R.M. (ed.). Flora
of tropical East Africa. Rotterdam: A.A. Balkema.
Cribb, P. 1989. Orchidaceae (Part 3). In Polhill, R.M. (ed.). Flora
of tropical East Africa. Rotterdam: A.A. Balkema.
Gentry, A. 1988. Changes in plant community diversity and floristic
composition on environmental and geographical gradients. Annals of the Missouri Botanical Garden 75: 1-34.
Grey-Wilson, C. 1980. Impatiens of Africa. Rotterdam: A.A. Balkema.
Grey-Wilson, C. 1982. Balsaminaceae. In
Polhill, R.M. (ed.). Flora of tropical
East Africa. Rotterdam: A.A. Balkema.
Leeuwenberg, A.J.M.
1979. The Loganiaceae of
Africa XVIII. Buddleja L. II. Revision of the African and Asian species. Mededeelingen van de Landbouwhogeschool te
Wageningen 79: 1-163.
Leroy, J.F. 1978. Composition, origin and affinities of the Madagascan
vascular flora. Annals of the Missouri
Botanical Garden 65: 535-589.
Lovett, J.C. 1993a. Eastern Arc moist forest flora. Pp. 33-55 in Lovett, J.C. and S.K. Wasser (eds.). Biogeography and ecology of the rainforests
of Eastern Africa. Cambridge, U.K.: Cambridge University Press.
Lovett, J.C. 1993b. Quantitative
descriptions of forests: quarter hectare strips. Unpublished manual.
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Uluguru Mountains Biodiversity Study: botanical survey and identification.
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conservation values and status of Kimboza Forest Reserve, Tanzania.
Mimeograph, University of Dar es Salaam.
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[1] The Ulugurus are sometimes regarded a centre of
radiation for Impatiens. However, the
endemics appear to come from a variety of sources.