Plant Communities and Tree Species Associations in a Miombo Ecosystem in the Lake Rukwa Basin, Southern Tanzania: Implications for Conservation

Journal of Ecology and the Natural Environment Vol. 3(2), pp. 63-71, February 2011 Available online at http://www.academicjournals.org/jene ISSN 2006- 9847 ©2011 Academic Journals Full Length Research Paper Plant communities and tree species associations in a Miombo ecosystem in the Lake Rukwa basin, Southern Tanzania: Implications for conservation Pantaleo K. T. Munishi1*, Ruwa-Aichi P. C. Temu1 and Soka G.2 1Department of Forest Biology, Sokoine University of Agriculture, P.O. Box 3010, Morogoro, Tanzania. 2Department of Wildlife Management, Sokoine University of Agriculture, P.O. Box 3010, Morogoro, Tanzania. Accepted 22nd December, 2010 This study assessed the plant communities and species associations in the eastern Miombo woodlands eco-region of the Lake Rukwa basin southern Tanzania. Information was collected from 288 temporary sample plots in 32 sampling sites established randomly in the area and covering as much variation in the landscape as possible. Detailed analysis of the vegetation identified six tree communities of conservation importance, which included Brachystegia boehmii-Pericopsis angolensis woodland, Julbernardia globiflora woodland, Combretum molle-Sclerocarya birrea-Combretum zeyherii-Acacia seyal var fistula woodland, Bridelia cathartica-Diospyros mespiliformis woodland, Brachystegia bussei- Pterocarpus tinctorius woodland and Brachystegia microphylla-Isoberlinia tomentosa-Hymenocardia acida- Syzygium owariense woodland. Majority of the described plant communities are typical of Miombo ecosystems dominated by trees belonging mainly to the genera Brachystegia and Julbernardia. A mixture of non-legume species but typical of the Miombo ecosystem, however, dominates two out of six described plant communities. Apparently, there is high variability of plant communities in the Miombo ecosystem of southern Tanzania, an indication of the diverse nature of the Miombo ecosystem, also, an implication of high species diversity. This documentation on the patterns of species assemblages is the beginning of unveiling the diversity of assemblage of species in dry forest ecosystems which occupy a wide area in the region. These associations are important targets for conservation and monitoring vegetation changes in this ecosystem. Key words: Miombo ecosystem, plant communities, species associations. INTRODUCTION The Miombo ecosystem is one of the tropical particularly species belonging to the Brachystegia, wildernesses in the world covering about 3.6 million km2 Julbernardia and Isoberlinia genera, which seldom occur and spanning ten countries in East and Central Africa. outside Miombo (Campbell et al., 1996). Much of the area Miombo woodlands form the dense forest woodland that covered by this ecoregion overlaps with White’s (1983) bisects Africa directly south of the Congo Basin and East floristically impoverished drier Zambezian Miombo African savannahs. It stretches all the way from Angola in woodland. The vegetation of this area is primarily the west to Tanzania in the east. These woodlands are woodland, dominated by trees in the legume sub-family dominated by trees of the subfamily Caesalpinioideae, Ceasalpinoideae with the genera Brachystegia, Julbernardia and Isoberlinia dominating and a well- developed underlying layer of grass. The dominance of one family of trees provides the unifying feature for this *Corresponding author. E-mail: [email protected]. ecosystem (Frost, 1996; Chidumuyo, 1997; WWF, 2001; Tel/Fax: 23260 4648, +255 754 591849. Byers, 2001; Timberlake, 2000). The Miombo ecosystem 64 J. Ecol. Nat. Environ. contains a diverse of major woodland types including wet broadleaf savannahs and woodlands interspersed with Miombo, dry Miombo, Burkea-Terminalia woodlands, areas of edaphic and secondary grassland. It forms the Baikiaea woodland, Mopane woodland, Acacia- westernmost part of the large Miombo woodland belt that Combretum woodland, dry evergreen forests is the dominant type of savannah woodland in the (Cryptosepalum), wetland grasslands and thickets (Itigi Zambezian center of endemism (White, 1983; Campbell thicket) (Byers, 2001). Dominant tree species include et al., 1996). Most of the Angolan Miombo woodland is Brachystegia spiciformis, Brachystegia boehmii, found at elevations between 1,000 and 1,500 m above Brachystegia allenii and Julbernardia globiflora (Campbell sea level. The mean annual rainfall in the ecoregion et al., 1996). In areas of higher rainfall, a transition to ranges from less than 800 mm in the south to about wetter Zambezian Miombo occurs (White, 1983). This 1,400 mm in the north and west (Huntley, 1974). vegetation supports greater floral richness and includes The region is home to at least 4,500 endemic plants almost all the Miombo dominants, such as Brachystegia species and 163 endemic animals’ species. It is a center floribunda, Brachystegia glaberrima, Brachystegia of diversity for underground trees whereby of the 98 taxifolia, Brachystegia wangermeeana, Brachystegia species known from Africa 86 are confined to this region. utilis, Marquesia macroura, Julbernadia globiflora, The Miombo ecosystem is also a globally important Julbernadia paniculata and Isoberlinia angolensis. carbon store. It is an area where humans have co- Deciduous riparian forest lines the numerous rivers in the evolved with wildlife over millions of years and contains area, while dry forest and thicket associations are also about 23 and 29% of the worlds black rhino and white found in the ecoregion, especially in rocky places. The rhino populations respectively, 42 to 45% of Africa’s Miombo ecosystem composes three major eco-regions elephant population, most of the Africa’s surviving wild which include the eastern Miombo woodlands (AT0706), dogs and over 66 million people and different livelihoods the Angola Miombo woodlands (AT0701) and the Central (White, 1983; WWF, 2001; Byers, 2001; Campbell, 1996; Zambezian Miombo woodlands (AT0704). Rodgers, 1996). The eastern Miombo woodlands ecoregion covers an According to WWF (2001), among the conservation area of about 483,900 square kilometers and consists of challenges of the Miombo ecosystem include maintaining a relatively unbroken area covering the interior regions of the habitat diversity and integrity, the hydrologic systems southeastern Tanzania and the northern half of and species diversity and status. Other challenges Mozambique, with a few patches extending into includes maintaining the biological and social values of southeastern Malawi. The ecoregion experiences a landscapes of biological significance, restoration of seasonal tropical climate with most rainfall concentrated degraded areas and those invaded by exotics and in the months from November through March followed by improving livelihoods by sustainable use of natural an intense drought that can last up to 6 months (Werger resources. Addressing such challenges needs an and Coetzee, 1978). Mean annual rainfall ranges effective long term conservation planning and priority between 800 and 1,200 mm, although, peaks of up to setting for resource management. The variability of the 1,400 mm per annum are found along the western region requires site-based approaches to conservation margins. though much larger landscape approaches may also be The Central Zambezian Miombo woodland ecoregion needed. The success of these approaches entails covers an area of 1,184,200 square kilometers and lies efficient assessment and appraisal of the resource status beyond Lake Malawi to the west, while to the north, the and distribution. While there is good knowledge on the ecoregion is bordered by Acacia-Commiphora bushland distribution and extent of the Miombo ecosystem in Africa and thicket belonging to the Somali-Masai phytochorion the plant community patterns and species association (White, 1983). The East African coastal mosaic of White’s which are important in holistic approaches to (1983) Zanzibar-Inhambane regional center of endemism conservation has not been well documented. This study lines the shore. The Zambezian and Mopane woodland assessed the plant communities and species ecoregion lies to the south. This ecoregion covers about associations in part of the vegetation of the eastern 70% of central and northern Zambia, the southeastern Miombo woodlands eco-region in Lake Rukwa basin, third of the Democratic Republic of Congo (DRC), Southern Tanzania. western Malawi, much of Tanzania and parts of Burundi and northeastern Angola. Consisting mainly of broadleaf, deciduous savannas and woodlands, it is MATERIALS AND METHODS characteristically interspersed with edaphic grassland Study site and semi-aquatic vegetation, as well as areas of evergreen groundwater forest. The extensive Angolan The study was conducted in the Lake Rukwa basin woodlands in Miombo woodlands (660,100 square kilometers) are part Chunya District southern Tanzania (Figure 1) as a representative of the eastern Miombo woodlands eco-region in Tanzania. The of an even larger Miombo ecosystem covers all of central woodlands are composed mainly of both wet and dry Miombo Angola and extends into the Democratic Republic of vegetation and some wetland/grassland patches with an area of Congo. This ecoregion comprises moist, deciduous 18,200 km-2 (Chunya District Socio-economic Profile, 1997). The Munishi et al. 65 Figure 1. Vegetation sampling points in the lake Rukwa basin woodlands. Lake Rukwa basin topography ranges from about 800 m on the acidic with low organic matter. shores of Lake Rukwa to a little bit above 1700 m above sea level

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