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Mahenge Scarp Forest Reserve: a biodiversity survey 4. RESULTS Survey work was conducted during the wet season between 10 th February and 18 th March 2003. Please refer to Appendix 2 for a detailed account of survey effort for each of the following research areas; flora, fauna and human resource-use. Appendices five to seven present vegetative data with appendices eight to 12 presenting faunal data. 4.1 Flora Vegetation types The vegetation of Mahenge Scarp FR is made up of patches of several different vegetation types: • Dry lowland forest - present at altitudes of around 500m. Found in the southern end of the FR. Canopy height greater than 10m, common tree genera include: Albizia, Sorindeia and Grewia (e.g. vegetation plot 11 and trapsite 3). • Scrub forest – intermediate in structure between lowland forest and bushland/thicket. Found in the southern part of the FR. Canopy height less than 10 metres, vines common. Common tree genera include: Makhamia lutea, Combretum exalatum, Grewia spp., Acalypha rosea, Magaritaria discoidea and Stereospernum kunthianum (e.g. vegetation plot 14). • Dry open woodland – at altitudes below 600m ground layer dominated by grasses. Found scattered in the FR. Dominant tree genera include Stereosperumum kunthianum, Diplorhynchus condylocarpon, Combretum molle, Terminalia sambesiaca and Sterculia appendiculata (e.g. vegetation plots 1 and 10). • Miombo woodland − open woodland found in the northern part of the FR. Dominated by Brachystegia spiciformis, Pterocarpus angolensis, Annona senegalensis, Combretum sp. and Milletia sp (e.g. vegetation plot 3 and trapsite 2). • Valley, swamp forest – found in the middle of the FR. Dominated by Bamboo species, Imperatum sp., Markhamia sp., Trichilia, Xeroderris sp. and Pterocarpus tinctoris. • Submontane forest – found at altitudes of 700m and above on the western part of the FR. Closed canopy at heights exceeding 30m. Dominant tree species include: Sorindeia madagascariensis, Trilepsium madagascariensis, Parkia filicoides, Albizia gummifera and Treculia africana. Herbs include: Dosternia holtzii, Justica sp., Maranthocloa leucantha and Impatiens sp. (e.g. vegetation plot 14 and trapsite 1). Intensive charcoal burning and timber extraction have been the major factors influencing vegetation physiognomy within Mahenge Scarp FR. Vegetation plots In total 20 vegetation plots were systematically placed throughout the reserve, sampling the six above vegetation types. The dominant vegetation type was woodland (45% of plots), with riverine forest, lowland forest and scrub thicket all found to be in 15% of the plots. Submontane forest and cultivation were 5% of the plots sampled. Forty percent of the vegetation had been affected by fire, with 15% by cutting and 5 % by cultivation, situated on the plateau of the escarpment. One vegetation plot had evidence of snare traps within it. Twenty five plant families and two unknown samples were recorded within the vegetation plots, with a total of 79 species within 63 genera. Most of the species found were common in woodland and forest habitats (see Appendix 7a), such as Combretum zehyeri, Brachystegia spiciformis, Stereospermum kunthianum and Piliostigma thonningii. Six forest dependent tree species were found within the higher submontane areas of the reserve. These were: Xylopia parviflora, Khaya anthotheca, Ficus vallis-chodae, Rytigynia digacantha, Aningeria adolfi- Frontier Tanzania Environmental Research Report 107 12
Mahenge Scarp Forest Reserve: a biodiversity survey friedericii and Sterculia appendiculata. Two near endemic species were identified, those limited to the Eastern Arc mountains and/or East African lowland forests: Dombeya shupangae and Grewia goetzeana. Charcoal producing species were present within the vegetation plots, such as Stereospermum kunthianum, Piliostigma thonningii, Dombeya shupangae and Annona senegalensis. Timber and carving species present within the reserve were: Lannea sp, Afzelia quanzensis, Dalbergia melanoxylon, Pterocarpus angolensis and Sterculia quinqueloba. Charcoal production was identified as the main threat to the FR, threatening the already small patches of good quality lowland and submontane forest along the escarpment, as well as the woodland with species such as Brachystegia spiciformis and Combretum spp also useful timber species. Other valuable species, found in abundance, are Milicia excelsa and Khaya anthotheca (African Mahogany). Bamboo was abundant within the reserve and used as building material by locals. In the woodland area of the FR, several species of trees were recognised as having medicinal uses for local people, as identified by a local elder. These were: Diprorhynchus condylocarpon, Annona senegalensis, Pterocarpus angolensis and Zanha golungensis. A worship site was also identified within dense submontane forest, which indirectly may help to conserve the forest by controlling timber cutting and charcoal production through cultural taboos. Regeneration plots Twenty regeneration plots were established within the FR. The regeneration of trees and shrubs is very limited in the dry woodland areas. In the lowland parts, tree species Trelepsium madagascariensis, Newtonia buchanannii, Sorindeiya madagascariensis, Parkia filcoides and Albizia sp. were regenerating. Opportunistic collections Casual observations and collections recorded 40 species within 19 families and 32 genera. Of these, 31 had not been recorded within the vegetation plots and consist of various lifeforms; 13 trees, six shrubs, seven herbs, four climbers and one grass species (see Appendix 7b). Pavetta crassipes is a near endemic tree species of the Eastern Arc mountains. The herbs were found within submontane forest. 4.2 Fauna Table 2 A summary of fauna recorded in Mahenge Scarp Forest Reserve (Appendix 8, 9, 10, 11 and 12) Taxa Number of families Number of species Mammals 14 27 Birds 30 81 Reptiles 7 16 Amphibians 5 12 Butterflies 5 77 Total 60 212 Mammals At least 27 species of native mammal representing 14 families were recorded in the reserve (Appendix 8). Although the identification of most species is certain, those of species that were captured remains tentative whilst awaiting taxonomic verifications (i.e. all small mammals, including bats) and some of the dung found could only be identified to genus. All taxonomy and nomenclature follows that of Kingdon (1997). Of the larger mammals recorded from the transects only eleven species were found, mostly in open woodland. These include browsers such as Bushbuck (Tragelaphus scriptus), Duiker and Dik dik (Madoqua kirkii), as well as Bushpig (Potamochoerus africanus), Aardvark (Orycteropus afer) and Banded Mongoose (Mungos mungo). Four primate species were recorded, three diurnal and common, the Vervet monkey (Cercopithecus aethiopicus pygerythrus), Yellow baboon (Papio cynocephalus) and the Blue monkey (Cercopithecus nictitans mitis). Vocalisations were recorded of the Mozambique or Grant’s galago Frontier Tanzania Environmental Research Report 107 13
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