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|Title: ||Vegetation History And Logging Disturbance: Effects On Rain Forest In The Lope Reserve, Gabon (With Special Emphasis On Elephants and Apes)|
|Authors: ||White, Lee JT|
|Supervisor(s): ||Rogers, Liz|
|Issue Date: ||Jul-1992|
|Publisher: ||University of Edinburgh; College of Science and Engineering; School of GeoScience|
|Abstract: ||An investigation of the effects of commercial mechanised selective logging
on rain forest vegetation and mammals, was undertaken in the Lope Reserve,
central Gabon, between January 1989 to July 1991. Vegetation in Lope is mostly
semi-evergreen lowland tropical rain forest, but there are some localised patches
of savanna., which are thought to be natural in origin, but which are maintained
today by regular f i r e s started by humans. Study sites were established in areas
of forest logged 20-25, 10-15, and 3-5 years previously.. a fourth was logged
during the study, and a f i f t h remained unexploited. None of the study sites had
been subject to hunting in the recent past.
A line-transect five kilometres in length was cut across the drainage in
each site. Forest composition and structure was assessed along each transect, by
identifying and measuring trees and lianes in botanical plots, counting stem density
of herbaceous vegetation i n the families Marantaceae and Zingiberaceae, and by
measuring canopy cover at three heights. At total of 4885 trees and lianes of 327
species occurred in five 2.5 ha samples of plants greater than 10 cm dbh, whilst
1832 individuals of 137 species were found i n five 25ha samples of trees greater
than 70cm dbh. There were marked differences i n structure and species
composition both between and within sites. A model was developed to attempt to
explain this variation, based upon the theory that much of Lope had been covered
by savanna vegetation during a previous cool., dry climatic phase, and that forest
structure and composition reflected recolonisation of the savanna by forest.
Physical features such as swamps, rocky outcrops and altitude were also
considered. Two types of multivariate analysis were applied to botanical data and
supported the model. The effects of logging on forest vegetation were assessed by
returning after logging to botanical plots established before exploitation. Damage
levels were low, compared to other parts of the World, resulting in about a 10%
reduction in canopy cover.
Patterns of f r u i t production were studied by counting fallen ripe and unripe
f r u i t on transects. Fruits encountered were classified on the basis of their
morphology and dispersal mechanism. There was a period of low f r u i t production
during the major dry season, when frugivores are likely t o suffer dietary stress.
A number of plant species which did produce f r u i t at this time were identified as species which might represent 'keystone' resources. Over 70% of f r u i t species
were animal-dispersed, demonstrating the the important role animals play in the
ecology of tropical rain forests.
Forest elephant (Loxodonta africana cyclotis) diet, ecological role and
group structure were analysed. The bulk of the diet consisted of the bark and
leaves of trees, and some monocotyledons in the families Marantaceae and
Zingiberaceae, but fruit was also important. Large-scale seasonal movements in
response to f r u i t availability were detected. Elephants were important seed
dispersers f o r many plant species, and were responsible for less than 1% of
natural tree mortality. The social structure of these forest elephants differed
from that of populations that have been studied i n east and southern Africa.
Average group size was 2.8, and no groups of more than 10 individuals were
Densi ties of primates, ungulates and squirrels were assessed using
standard line-transect censuses. Resolution was poor, but statistical differences
were detected between sites for some species. Chimpanzee, (Pan t. troglodytes)
densities declined i n logged forest, but no other species could be shown to decline
after logging. Some other differences between sites were related to vegetation
composition. Biomass was high, estimated a t up to 4692.6 kg km-2, but was
dominated by elephants, which made up 25-82%.
Conservation implications of this study are discussed, and recommendations
|Sponsor(s): ||Leverhulme Trust.
Wildlife Conservation International (the conservation branch of the New York Zoological Society).
The Royal Society (London).
The Conder Conservation Trust.
The Richard Brown Scholarship (University of Edinburgh.)
The Conrad Zweig Trust.
Mr Sebastian Clairmonte.
Centre International de Recherches Médicales de Franceville|
|Appears in Collections:||Global Change Research Institute PhD thesis collection|
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