There is high deforestation and forest degradation estimated to be 400,000ha per annum between 1990 and 2013 in Tanzania forests. This is due to the increase in wood demand for energy and for industrial raw materials. The study was conducted to assess forest condition of Sokoine University of Agriculture - Kitulangalo Forest Reserve (SUA KFR). A total of 52 nested circular plots with radii of 2, 5, 10, and 15 m were used to collect data such as diameter at breast height (DBH), height and number of regenerants. Parameters computed for data analsysis were stem per ha (N), number of regenerants, dominant tree species, exotic species, basal area per ha (G) and volume (standing and removed) per ha (V). A total of 71 tree species were identified and recorded during inventory, the average 995±256 stems/ha of different tree species of various DBH class, the average basal area per ha, G=7.961268±0.8 m2/ha and the mean standing total volume, 54.72914±11.3 m3/ha were also computed. The mean total volume removed is 0.58 m3 per ha which is very small compared to stocking. The dominant tree (richness) species includes Julbernardia globiflora (17%), Brachystegia speciformis (8%), Acacia nigrescens (7%), Acacia robusta (6%), Albizzia harveyi (5%), Scierocaryabirrea spp/ Caffra (5%) and others i.e total of all <5% (52%). The conducted inventory shown that there is an average of 6121±2777regenerants per ha. Only Senna siamea was identified as exotic species which planted beside the forest boundary as a demarcation. In general, forest structure parameters indicate that SUA KFR is in a good condition as have high species richness and stem density per ha. We recommend more research on assessing forest condition in other forests in order to be aware with their status and look forward for the proper management measures.
Keywords: forest, condition, miombo, stem per ha, basal area per ha, volume
Miombo woodlands cover a vast area of south and central Africa. Stretching from the northernmost tip of South Africa up to Tanzania, and from Mozambique in the east to Angola in the west, they cover approximately 3.2 million km2 (Scholes & Biggs 2004). Fires are the characteristic feature of the miombo woodlands. More detailed descriptions of miombo and how it is differentiated from other savanna or forest types are provided by Huntley (1982), Chidumayo (1993) and Frost (1996). Tanzania has about 48 million hectares of forests and woodlands which is about 55% of the total country land area (Mgoo, 2013). Out of this total area, almost two thirds consists of woodlands on public lands which lack proper management. Public lands are under enormous pressure from expansion of agricultural activities, livestock grazing, fires and other human activities. About 13 million hectares of this total forest area have been gazetted as forest reserves. Over 80 000 hectares of the gazetted area is under plantation forestry and about 1.6 million hectares are under water catchment management. The forests offer habitat for wildlife, beekeeping, unique natural ecosystems and genetic resources. They are also an important economic base for the country's development. Miombo is characterized by Brachystegia and an understory of grasses, often growing on nutrient-poor soils derived from acid crystalline bedrock. In addition to Brachystegia, other important tree genera are Julbernardia and Isoberlinia (Campbell, Frost & Byron, 1996). Closely associated species of Miombo woodland are Pterocorpus angolensis, Vangueria spp, Vitex spp, Combretum spp and Dalbergia spp. The undergrowth is dominated by a heliophilous grass layer and forbs. Dominant grass species include Hyparrhenia spp,Themeda triandra and Panicum maximum and most common forbs are Indigofera spp. Patches of semievergreen forest (Kielland-Lund 1990) are more conspicuous in the western part of the reserve along the base of Kitulanghalo Hill where the tree layer is dominated by Manilkarasulcata and Scodophloeusfischeri. Common smaller trees are Cola clavata and Strychnoshenningsii. This tree species grow in areas where the climate is characterized by mean annual temperatures and precipitation of 18.0-23.1 ̊ C and 710–1365 mm (Frost, 1996).Miombo savannahs are home to important animal populations including elephants, lions, buffalos and antelopes and have high bird diversity (Campbell, Frost & Byron, 1996; Frost, 1996). Additionally, the miombo woodland ecosystem represents an important supply of fuel wood, fruits, poles and timber in villages, periurban and urban areas (Desanker et al., 1997; Sileshiet al., 2007).The Sokoine University of Agriculture - Kitulangalo forest reserve (SUA-KFR) covers 600ha out of the main Kitulangalo Forest Reserve comprised of 2638 ha. SUA-KFR is an important watershed management and soil conservation areas that contribute to urban water supply in Dar essalaam city through Sangasanga river which pours its water into Ngerengere river among the main tributaries of Ruvu river a major source of water to the city. Although the management of SUA KFR entails total conservation, there are noted areas for revenue collection like eco-tourism, beekeeping, collection and sell of non-wood products. The communities adjacent to SUA KFR in the two villages (Maseyu and Gwata) are collecting revenue from few researchers who visit the forest reserve. Biodiversity value, amelioration of climate, honey collection from tree boles, hunting of animals to increase food varieties, medicines, collections of vegetables, mushrooms, fruits and insects (sondo), fuelwood, construction materials and source of water for irrigation and drinking are potential values of SUA KFR. Eco-tourism provisions, local employment for casual labour and social values form important potentials to the local communities. Research and training together with the eco-tourism and carbon sequencing are potential for national and international communities. Being a natural forest of higher biodiversity values, SUA KFR has a great chance to qualify for Carbon credit. Despite of all these advantages offered by many forest still deforestation and forest degradation estimated to be 400,000ha per annum between 1990 and 2013 in Tanzania forests (FAO 2011; Mgoo 2013). There is need to be aware with the status of forests in order to take appropriate measures to ensure availability of forest resources for the benefit of present and future generations. This study was conducted to assess forest condition such as stem per ha, number of regenerants, dominant tree species, exotic species, basal area per ha, standing and removed volume per ha of SUA KFR.
Materials and methods
Kitulangalo is located at almost 35 km east of Morogoro municipality alongsideMorogoro–Dar es salaam high way, the major means of transport for the people and forest products to urban and commercial centers such as Dar es Salaam and Morogoro. Morogoro municipality is about 200km west of Dar es Salaam city.
The predominant feature in Kitulangalo is the Kitulangalo hill, which is about 762m above sea level situating at 060 39’-6043’S and 37057 -38001’E on the left hand side when coming from Morogoro. The reserve is highly accessible throughout the year season since it’s only few meters alongside the Morogoro-Dar es salaam highway, only 35km from the Morogoro municipality in Gwata-ujembe and Maseyu villages.This lead the forest to be open for easy access to the interior. (Figure 1)
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Figure 1: A map showing a location of SUA-KFR. (Source; Nduwamungu, J. et al., undated)
The SUA – KFR map was used to guide the inventory operation in the field. Also systematic sampling design was used, where the plots were located in transects and distance between plots and between transect were 320m and 320m respectively.. The Concentric circular plots with various radiuses were adopted during inventory as shown figure 2 below;
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Figure 2: Concentric circular plots
Distance between transects and between plots
The longest forest boundary length is that along Dar es Salaam- Morogoro road, it is about 3200m and the whole SUA-KFR is to be laid out with 10 transects, hence the ground distance between transects is given by
3200m/ 10 = 320m
The first transect was laid at 160m from the boundary and all transects were laid at the forward bearing of 310⁰ to the north in which its back bearing was 130⁰
The number of plots in an inventory is usually calculated using data from a pilot study, the number of sampling plots is set to be 52 and plot area is set to be 0.070686 ha in which its radius is set to be 15m
The distance between plots is calculated as follows;
A = Area of the forest, 600ha
n = number of sample plots, 52 plots
Area (a) of the forest represented by plots, therefore is given by A/n, 10.3846ha (103,846.15m2)
Distance between plot =Abbildung in dieser Leseprobe nicht enthalten, Abbildung in dieser Leseprobe nicht enthalten= 322m~320m
Allocation of sample plots
Systematic allocation of the sample plots along transect line was applied. This was adapted due to the fact that among the advantages of systematic sampling design it ensures coverage of the whole population and it’s easy in allocation of sampling plots. Plot shape chosen was circular plots since it serves time and increase accuracy. Measurementswere done into four concentric plots of radius 2m, 5m, 10m, 15m and.
The plot area in ha was calculated by πr2/10,000
The result were that in radius of; 2m the area is 0.001257m2
5m is 0.00785m2
10m is 0.0314m2 and in
15m radius is 0.07069m2
Trees parameters measured and other forest resources
i. In 2m radius we counted all seedlings, identified grasses and herbs.
ii. In 5m radius we measured all trees DBH>1cm.
iii. In 10m radius we measured all trees with DBH>10cm.
iv. In 15m radius all trees and shrubs with DBH>20
v. All the stumps within the sample plot were measured.
The height of three trees, largest, medium and small in terms of DBH were measured using the hypsometer and their height were assumed respectively.