This study investigates the structure, species composition, and diversity of a section of the Kilengwe Forest in Tanzania. In order to accomplish the proposed objectives, 18 plots of 20？m × 20？m were randomly established in the forest and the number of tree species in each plot was identified and counted. The most important families and species were determined using importance value indices at the respective taxonomic levels. Diversity was measured using the Shannon-Wiener and Fisher alpha diversity indices. A total of 276？stems/ha representing 93？species/ha within 26 families were documented from 0.72？ha. Fabaceae and Julbernadia globiflora were the dominant family and species, respectively. Seventy-eight percent of the total species were rare. The average basal area of the forest was 7.1？m2/ha. The Shannon-Wiener index (4.02) and Fisher’s alpha diversity (35.5) indicated high species diversity within the forest. The species-area and species-abundance curves revealed an escalating trend implying that more sampling efforts could result in a higher number of species existing in the forest. The size class distribution displayed a reverse J-shaped pattern; however, the larger size classes DBH >50？cm were not represented. The study suggests the necessity for anthropogenic disturbance control as this is the major source of forest degradation in the studied area. 1. Introduction Globally, 52% of the total forests are in tropical regions and they are known to be the most important areas in terms of biodiversity [1]. Local communities living nearby depend on these forests for their livelihoods. For instance, forest trees provide resources like food, traditional medicine, energy, timber, shade, and habitats for other organisms [2]. The rapid increase in human population near forest ecosystems has increased threats of degradation and fragmentation to these ecosystems [3]. In Tanzania, the rate of population increase per year is 2.7% with the majority of people living in rural areas where forests are located. The annual loss of forest cover in the country has increased by 37% from the period of 1990–1995 (322,000？ha/year) to 2000–2010 (403,000？ha/year). The loss is mainly due to agricultural clearings, overgrazing, charcoaling, firewood, and timber harvesting [3, 4]. Like other tropical forests in the world, the Kilengwe Forest suffers extensive loss and degradation from anthropogenic activities and sporadic fire, which have a strong effect on the structure and species composition of the forest [5]. The quantification of the structure and diversity of tree species
References
[1]
L. R. Holdridge, Life Zone Ecology, Tropical Science Center, San Jose, Costa Rica, 1967.
[2]
D. S. Kacholi, Effects of habitat fragmentation on biodiversity of Uluguru Mountain forests in Morogoro region, Tanzania [Ph.D. thesis submitted at Georg-August University Goettingen], Cuvillier Verlag, Goettingen, Germany, 2013.
[3]
“Global forest resources assessment 2010,” Main Report. FAO Paper 163, Food and Agriculture Organization of the United Nation (FAO), Rome, Italy, 2010.
[4]
W. D. Newmark, Conserving Biodiversity in East African Forests. A Study of the Eastern Arc Mountains, Springer, New York, NY, USA, 2002.
[5]
S. Madoffe, G. D. Hertel, P. Rodgers, B. O'Connell, and R. Killenga, “Monitoring the health of selected eastern arc forests in Tanzania,” African Journal of Ecology, vol. 44, no. 2, pp. 171–177, 2006.
[6]
R. Condit, S. P. Hubbell, J. V. Lafrankie et al., “Species-area and species-individual relationships for tropical trees: a comparison of three 50-ha plots,” Journal of Ecology, vol. 84, no. 4, pp. 549–562, 1996.
[7]
A. H. Gentry, “Tropical forest biodiversity: distributional patterns and their conservational significance,” Oikos, vol. 63, no. 1, pp. 19–28, 1992.
[8]
S. A. Mori, B. M. Boom, A. M. Carvalho de, and T. S. Dos Santos, “Ecological importance of Myrtaceae in an Eastern Brazilian West Forest,” Biotropica, vol. 15, no. 1, pp. 68–70, 1983.
[9]
J. T. Curtis and R. P. McIntosh, “The interrelations of certain analytic and synthetic of phytosociological characters,” Ecology, vol. 31, pp. 434–455, 1950.
[10]
R. M. Seaby and P. A. Henderson, Species Diversity and Richness Version 4, Pisces Conservation, Lymington, UK, 2006.
[11]
A. N. Magurran, Measuring Biological Diverisy, Blackwell Science, Melden, Germany, 2004.
[12]
R. E. Malimbwi, D. Shemweta, E. Zahabu, S. P. Kingazi, J. Z. Katani, and D. A. Silayo, “Forest inventory for mvomero district, Morogoro-Tanzania,” FORCONSULT Unpublished Report, 2005.
[13]
E. N. Mwavu, Human impact, plant communities, diversity and regeneration in Budongo forest reserve, North-Western Uganda [Ph.D. thesis], University of the Witwatersrand, Johannesburg, South Africa, 2007.
[14]
K. Z. Doody, A. Ntemi, R. Killenga, and N. K. Beharrell, “Vegetation in mpanga village forest reserve: a biodiversity survey,” East Usambara Conservation Area Management Programme Technical Paper 51, Frontier Tanzania: Forestry and Beekeeping Division and Mets？hallitus Consulting, Dar es Salaam, Tanzania, Vantaa, Finland, 2011.
[15]
A. Gentry, “Changes in plant community diversity and floristic composition on environmental and geographical gradients,” Annals of Missouri Botanical Garden, vol. 75, pp. 1–34, 1988.
[16]
P. Addo-Fordjour, S. Obeng, A. K. Anning, and M. G. Addo, “Floristic composition, structure and natural regeneration in a moist-semi deciduous forest following anthropogenic disturbances and plant invasion,” International Journal of Biodiversity and Conservation, vol. 1, no. 2, pp. 021–037, 2009.
[17]
N. D. Burgess and C. Muir, “Coastal forests of Eastern Africa: Biodiversity and Conservation,” in Proceedings of the Workshop held at the University of Dare s Salaam, Society for Environmental Exploration/Royal society for the protection of birds, Frontier, UK, August 1994.
[18]
S. P. Rwamugira, Impact of mining on forest ecosystem and adjacent communities of Eastern Arc Mountains. A case study of Ruvu catchment forest reserve [M.S. thesis], Sokoine University of Agriculture, 2008.
[19]
N. D. Burgess and G. P. Clarke, “The coastal forests of Eastern Africa,” IUCN: Cambridge and Gland, 2000.
[20]
F. Wittmann, J. Sch？ngart, J. C. Montero et al., “Tree species composition and diversity gradients in white-water forests across the Amazon Basin,” Journal of Biogeography, vol. 33, no. 8, pp. 1334–1347, 2006.
[21]
H. Zegeye, D. Teketay, and E. Kelbessa, “Diversity, regeneration status and socio-economic importance of the vegetation in the islands of Lake Ziway, South-Central Ethiopia,” Flora, vol. 201, no. 6, pp. 483–498, 2006.
[22]
N. J. Gotelli and R. K. Colwell, “Estimating species richness,” in Biological Diversity: Frontiers and Measurement and Assessment, A. E. Magurran and B. J. McGill, Eds., Oxford University Press, New York, NY, USA, 2011.
[23]
P. A. Schwarz, T. J. Fahey, and C. E. McCulloch, “Factors controlling spatial variation of tree species abundance in a forested landscape,” Ecology, vol. 84, no. 7, pp. 1862–1878, 2003.
[24]
L. S. Comita, R. Condit, and S. P. Hubbell, “Developmental changes in habitat associations of tropical trees,” Journal of Ecology, vol. 95, no. 3, pp. 482–492, 2007.
[25]
S. P. Hubbell, J. A. Ahumada, R. Condit, and R. B. Foster, “Local neighborhood effects on long-term survival of individual trees in a neotropical forest,” Ecological Research, vol. 16, no. 5, pp. 859–875, 2001.
[26]
J. C. Ingram, T. P. Dawson, and R. J. Whittaker, “Mapping tropical forest structure in southeastern Madagascar using remote sensing and artificial neural networks,” Remote Sensing of Environment, vol. 94, no. 4, pp. 491–507, 2005.
[27]
R. Pardini, S. M. de Souza, R. Braga-Neto, and J. P. Metzger, “The role of forest structure, fragment size and corridors in maintaining small mammal abundance and diversity in an Atlantic forest landscape,” Biological Conservation, vol. 124, no. 2, pp. 253–266, 2005.
[28]
T. C. Whitmore, An Introduction to Tropical Rainforests, Oxford University Press, Oxford, UK, 2nd edition, 1998.
[29]
S. Hadi, T. Ziegler, M. Waltert, and J. K. Hodges, “Tree diversity and forest structure in northern Siberut, Mentawai islands, Indonesia,” Tropical Ecology, vol. 50, no. 2, pp. 315–327, 2009.
[30]
A. Ahrends, Patterns of degradation in lowland coastal forests in coastal region Tanzania [M.S. thesis], Ernst-Moritz-Arndt University, Greifswald, Germay, 2005.
[31]
R. B. Modest, S. L. S. Maganga, S. N. Hassan, S. B. Mariki, and M. Muganda, “Population structure and extraction of three commercial trees in Nguru ya Ndege forest reserve, Morogoro-Tanzania,” Ethiopian Journal of Environmental Studies and Management, vol. 3, no. 3, pp. 41–48, 2010.
