Diversity, distribution, and conservation status of forest tree species in cross river state, Nigeria


  • Patrick Ishoro Akwaji Department of Plant and Ecological Studies, Faculty of Biological Sciences, University of Calabar, Calabar, Cross River State, Nigeria
  • Glory Nicholas Oden Department of Plant and Ecological Studies, Faculty of Biological Sciences, University of Calabar, Calabar, Cross River State, Nigeria
  • Dough Owojoku Onah Department of Plant and Ecological Studies, Faculty of Biological Sciences, University of Calabar, Calabar, Cross River State, Nigeria
  • Ekemg Ita Okon Department of Plant Sciences and Biotechnology, Faculty of Biological Sciences, Cross River University of Technology, Calabar, Cross River State, Nigeria
  • Linus Bashie Ajikah Department of Plant and Ecological Studies, Faculty of Biological Sciences, University of Calabar, Calabar, Cross River State, Nigeria
  • Ferdinand Akpo Akomaye Department of Plant and Ecological Studies, Faculty of Biological Sciences, University of Calabar, Calabar, Cross River State, Nigeria




Biodiversity, Forest survey, IUCN


Tree species diversity plays a central or decisive function in ecosystem operations, delivering palpable and impalpable advantages. The periodical evaluation of forest trees is absolutely necessary for the management and conservation goals. Our study employed the modified Whittaker sampling method to survey the diversity and distribution of tree species in 22 forested sites across the northern, central, and southern geographical zones of Cross River State, Nigeria. Only tree species (dbh ≥ 10 cm) present in our sampled plots were identified and recorded. The conservation status of identified forest tree species was checked using the IUCN red list categories and Criteria 2021: ver. 3.3.1-second edition. Field studies were undertaken from April 2019 – October 2020. A total of 197, 249, and 229 tree species belonging to 49, 50 and 49 families were recorded in the northern, central and southern geographical zones, respectively. A total of 403 tree species belonging to 65 families was recorded across the study area, of which 55, 79 and 78 tree species were localized to the northern, central and southern geographical zones, respectively. The Fabaceae was the most dominant family (64 species) while twenty families had one species each. The Cross River National Park (CRNP), Okwangwo Division had the highest number of tree species (171) while Adiabo community forest had the lowest (26). The CRNP, Okwangwo Division exhibited the highest species richness (11.39) and diversity index (4.75) while Adiabo community had the lowest species richness (4.47) and diversity index (1.14). The Least Concern conservation status had the highest number of species (226) while the Critically Endangered and Data Deficient had the lowest (1 each). Our findings will assist accord policymakers or stakeholders the information obligatory for implementing a forestry blueprint and plan of action or scheme in Cross River State, Nigeria.


Abgogidi, O. M. (2011). A survey of the economically valued forest plant species at the

proposed site for airport in Asaba, Delta State, Nigeria. Agriculture and Biology Journal of North America, 2(1), 143-149.

Adeduntan, S. A. (2009). Influence of human activities on diversity and abundance of insects in Akure Forest Reserve, Ondo State, Nigeria. International Journal of Biological and Chemical Sciences, 3(6), 1320-1335.

Adekunle, V. A. J. & Akinlembola, O. (2008). Effect of deforestation on climate change and global warming in Nigeria. In: Popoola, L. (ed.). Proceedings of the 32nd Annual Conference of the Forestry Association of Nigeria (FAN) held at Umuahia, Abia State on 20-24th October, 170-182Pp.

Adekunle, V. A. J. & Olagoke, A. O. (2008). Diversity and bio-volume of tree species in natural forest ecosystem in the bitumen-producing area of Ondo State: A baseline study. Biodiversity and Conservation, 17, 2735-2755.

Adekunle, V. A. J. (2006). Conservation of trees species diversity in tropical rainforest ecosystem of South West Nigeria. Journal of Tropical Forest Sciences, 3(1), 91-101.

Adekunle, V. A. J. (2007). Non-linear regression models for timber volume estimation in natural forest ecosystem, Southwest Nigeria. Research Journal of Forestry, 1(2), 40-54.

Adekunle, V. A. J., Akindele, S. O. & Fuwape, J. A. (2004). Structure and yield models of tropical lowland rainforest ecosystem of Southwest Nigeria. Food, Agriculture and Environment, 2(2), 395-399.

Adekunle, V. A. J., Olagoke, A. O. & Akindele, S. O. (2013). Tree species diversity and structure of a Nigerian Strict Nature Reserve. Tropical Ecology, 54(3), 275-289.

Adekunle, V. A. J., Olagoke, O. A. & Ogundare, L. F. (2010). Rate of timber production in a tropical rainforest ecosystem of southwest Nigeria and its implications on sustainable forest management. Journal of Forestry Research, 21, 225-230.

Adeyemi, A. A., Ibe, A. E. & Okedimma, F. C. (2015). Tree structural and species diversities in Okwangwo Forest, Cross River State, Nigeria. Journal of Research in Forestry, Wildlife and Environment, 7, 36-53.

Adeyemi, A. A., Jimoh, S. O. & Adesoye, P. O. (2013). Assessment of tree diversities in Oban Division of the Cross River National Park (CRNP), Nigeria. Journal of Agriculture, Forestry and the Social Sciences, 11(1), 216-230.

Agbor, C. O. (2003). An ecological basis for the management of Afi Mountain Wildlife Santuary, Cross River State. Unpublished PhD thesis, Department of Wildlife and Fisheries Management, University of Ibadan, 119-210Pp.

Aigbe, H. I. & Omokhua, G. E. (2015). Tree species composition and diversity in Oban Forest Reserve, Nigeria. Journal of Agricultural Studies, 3(1), 10-24.

Aigbe, H. I. Akindele, S. O. & Onyekwelu, J. C. (2014). Tree species diversity and density pattern in Afi River Forest Reserve, Nigeria. International Journal of Scientific and Technology Research, 3(10), 178-185.

Ajayi, S. & Obi, R. L. (2016). Tree species composition, structure and importance value index (IVI) of Okwangwo Division, Cross River National Park, Nigeria. International Journal of Science and Research, 5(12), 85-93.

Aju, P. C. & Ezeibekwe, I. O. (2010). Understanding and appreciating the need for biodiversity conservation in Nigeria. Journal of Medicinal Plants Research, 42, 2605-2608.

Akwaji, P. I. & Edu, E. A. (2017). Population frequency, density, abundance and diversity of tree species in ten communal forests of Nortehrn Cross River State, Nigeria. International Journal of Current Research, 9(10), 59581- 59596.

Amazon Watch (2021). The Amazon rainforest. Available at: https://amazon watch.org.

Amissah, L., Godefridus, M., Mohren, J., Frans Bongers, W., Hawthorne, D. and Poorter, L. (2014). Rainfall and temperature affect tree species distribution in Ghana. Journal of Tropical Ecology, 30, 435-446.

Amonum, J. I., Dau, J. H. & Gbande, S. (2016). Composition and distribution of economic tree species in Nagi Forest Reserve, Benue State, Nigeria. Journal of Research in Forestry, Wildlife and Environment, 8(4), 101-108.

Aregheore, E. M. (2009). Country Pasture/Forage Resource Profiles Nigeria. Food and Agriculture Organization of the United Nations (FAO) Rome, Italy. 42Pp.

Asanok, L. & Marod, D. (2016). Environmental factors influencing tree species regeneration in different forest stands growing on a limestone hill in Phrae Province, Northern Thailand. Journal of Environmental Science, 32, 237-252.

Asanok, L., Kamyo, T., Norsaengsri, M., Salinla-um, P., Rodrungruang, K., Karnasuta, N., Navakam, S., Pattanakiat, S., Marod, D., Duengkae, P. & Kutintara, U. (2017). Vegetation community and factors that affect the woody species composition of riparian forests growing in an urbanizing landscape along the Chao Phraya River, Central Thailand. Urban for Urban Green, 28, 138-149.

Austin, M. P., Pausas, J. G. & Nicholls, A. O. (1996). Patterns of tree species richness in relation to environment in South Eastern New South Wales. Australian Journalof Ecology, 21, 154-164.

Avery, T. E. & Burkhart, H. E. (2002). Height measurement principles. Forest measurements (5thed).New York, McGraw-Hill, 154Pp.

Baltzer, J. L., Davies, S. J., Bunyavejchewin, S. & Noor, N. (2008). The role of desiccation tolerance in determining tree species distributions along the Malay–Thai Peninsula. Functional Ecology, 22, 221-231.

Bello, A. G., Isah, A. D. and Ahmad, B. (2013). Tree species diversity analysis of Kogo Forest Reserve in North Western Nigeria. International Journal of Plant, Animal and Environmental Sciences, 3(3), 189-196.

Bisong, F. E. & Mfon, P. Jnr (2006). Effect of logging on stand damage in rainforest of south-eastern Nigeria. West African Journal of Applied Ecology, 10, 119- 129.

Blanc, l., Maury-lechon, G. & Pascal, J. P. (2000). Structure, floristic composition and natural regeneration in the forests of Cat Tien National Park, Vietnam: an analysis of the successional trends. Journal of Biogeography, 27, 141-157.

Breteler, F. J. (1991). Dichapetalaceae. In: Polhill, R, M. (edition.). Flora of Tropical East Africa. A. A. Balkerma, Rotterdam, Netherlands. 18Pp.

Buba, T. (2015). Impacts of different tree species of different sizes on spatial distribution of herbaceous plants in the Nigerian guinea savannah ecological zone. Scientifica, 20(15), 1-8.

Burkill, H. M. (1985). The useful plants of West Tropical Africa. 2nd Edition. Vol.1, Families A-D. Royal Botanic Gardens, Kew, Richmond, United Kingdom, 960Pp.

Campbell, D. G. Stone, J. L. & Rosas, A. Jr. (1992). A comparison of phytosociology and dynamics of three flood plains (Varzea) forests of known age, Rio Jurua, Western Brazilian Amazon. Botany Journal of the Linnaean Society, 108, 213-237.

Colinvaux, P. A., Oliveira, P. & De E. (2000). Palaeoecology and climate of the Amazon basin during the last glacial cycle. Journal of Quaternary Science, 15 (4), 347-356.

De Grammont, P. C. & Cuaron, A. D. (2006). An evaluation of threatened species categorization systems used on the American continent. Conservation Biology, 20(1), 14-27.

Deka, J., Tripathi, P. O. & Khan, L. M. (2012). High dominance of Shorea robusta Gaertn. in Alluvial Plain Kamrup Sai Forest of Assam, Northeast India. International Journal of Ecosystems, 2(4), 67-73.

Dexter, K. & Chave, J. (2016). Evolutionary patterns of range size, abundance and species richness in Amazonian angiosperm trees. Peer Journal, 4, e2402.

Duran, E., Meave, J. A., Lott, D. J. & Segura, G. (2006). Structure and tree diversity patterns at landscape level in a Mexican tropical deciduous forest. Boletin de Sociedad Botanica de Mexico, 79, 43-60.

Edet, D. I., Ijeoma, H. M. & Ogogo, A. U. (2012). Preliminary assessment of tree species diversity in Afi Mountain Wildlife Sanctuary, Southern Nigeria. Agriculture and Biology Journal of North America, 3(12), 486-492.

Egbe, E. A., Chuyong, G. B., Fonge, B. A. & Namuene, K. S. (2012). Forest disturbance and natural regeneration in African rainforest at Korup National Park, Cameroon. International Journal of Biodiversity and Conservation, 4 (11), 377-384.

Eilu, G., Hafashimana, D. L. N. & Kasenene, J. M. (2004). Density and species diversity of trees in four tropical forets of the Albertine rift, Western Uganda. Diversity and Distribution, 10, 303-312.

Engelbrecht, B. M., Comita, L. S., Condit, R., Kursar, T. A., Tyree, M. T., Turner, B. L. & Hubbell, S. P. (2007). Drought sensitivity shapes species distribution patterns in tropical forests. Nature, 447, 80-82.

FAO (2009). The State of the World’s Forests 2009. Food and Agriculture Organization of the United Nations, Rome. 122Pp.

FAO (2010). Global Forest Resources Assessment 2010. Food and Agriculture Organization of the United Nations, Rome. 89Pp.

Fitter, R. & Fitter, M. (1987). The road to extinction problems of categorizing the status of taxa threatened with extinction. IUCN Gland, Switzerland and Cambridge, UK.

FME (2006). Federal Government of Nigeria Approved National Forest Policy 2006. Federal Ministry of Environment of Nigeria, Abuja.

Gebreselassen, G. V. (2011). Plant community’s species diversity seedling bank and resprouting in Nandi Forest, Kenya. Ph.D Thesis, Universitat Koblenz-Landau.

Goudie, A. S. (2005). The Human Impact on the Natural Environment: Past, Present, and Future. London (UK), Wiley-Blackwell.

Gower, S. T., Landberg, J. J. & Bisbee, K. E. (2003). Forest biomes of the World. In: Young R.A and Gies,R.L (Eds): Introduction to ecosystem science and and management. 3rd edition, John Wiley and Sons Inc, U.S.A., 57-745Pp.

Hamann, A., Barbon, E. B., Curio, E. & Madulid, D. A. (1999). A botanical inventory of a submontane tropical rainforest on Negros Island, Philippines. Biodiversity and Conservation, 8, 1017-1031.

Han, H., Jang, K., Song, J., Seol, A., Chung, W. & Chung, J. (2011). The effects of site factors on herb species diversity in Kwangneung forest stands. Forest Science and Technology, 7, 1-7.

Hawthorne, W. D. and Gyakari, N. (2006). Photo guide for the forest trees of Ghana. A tree-spotter’s field guide for identifying largest trees. Oxford Forestry Institute, Oxford, 432Pp.

Herrick, J. E., Van Zee, J. W., Havstad, K. M., Burkett, L. M. and Whitford, W. G. (2005). Monitoring manual for grassland, shrubland and savanna ecosystems.Volume 2. Tucson, University of Arizona Press, 1-200Pp.

Holmgren, M. & Pourter, L. (2007). Does aruderal strategy dominate the endemic flora of the West African forests? Journal of biogeography, 34: 1100-1111.

Hossain, M. K., Abdul, A., Saddam, H., Md.Akter, H. & Anisur, R. (2019). Diversity and conservation status of tree species in Hazarikhil Wildlife Sanctuary (HWS) of Chittagong, Bangladesh. Geology, Ecology and Landscapes, 4(4), 298-305.

Hossen, S. & Hossain, M. K. (2018). Conservation status of tree species in Himchari National Park of Cox’s Bazar, Bangladesh. Journal of Biodiversity, Conservation and Bioresource Management, 4(2), 1-10.

Hutchinson, J & Dalziel, J. (1972). Flora of West Tropical Africa. Volume .3 (1,2) 2nd Edition. Milbank, London, Crown Agents for Overseas Governments and Administrators, 1-276Pp.

Ige, P. O. (2011). Stem Diameter Distribution Models for a Natural Stand in Shasha Forest Reserve, Nigeria. M.Sc. Thesis submitted to the Department of Forest Resources Management, University of Ibadan, Nigeria, 75-86Pp.

Ihenyen, J., Okoegwale, E. E. & Mensah, J. K. (2009). Composition of tree species in Ehor Forest Reserve, Edo State. Nature and Science, 7(8), 8-18.

Ikyaagba, T. E, Tee, T. N., Dagba, B. I., Ancha, U. P., Ngibo, K. D. & Tume, C. (2015). activities on vegetation of Olokemeji Forest Reserve. Global Nest: The International Journal, 6(2), 130-139.

Iroko, O. A., Kareem, A. A., Adio, A. F. & Gbadebo, J. O. (2008). Impact of human activities on the forest and their effects on climate change. In: Popoola, L. (ed.). Proceedings of the 32nd Annual Conference of the Forestry association of Nigeria (FAN) held at Umuahia, Abia State on 20-24th October, 208-214Pp.

IUCN (2004). 2004 IUCN Red List Categories and Criteria, IUCN, Gland Switzerland. Available at: www.iucnredlist.org.

IUCN (2010). Plants under pressure – a global assessment. The first report of the IUCN Sampled Red List Index for Plants. Royal Botanic Gardens, Kew, UK, Natural History Museum, London, and International Union for Conservation of Nature.

IUCN (2012). IUCN Red List Categories and Criteria: Version 3.1. Second edition. Gland, Switzerland and Canbridge, IUCN, UK.

IUCN (2021). IUCN Red List Categories and Criteria 2021: Version 3.1 second edition, IUCN, Gland, Switzerland. Available at: www.iucnredlist.org.

Jimoh, S. O., Adesoye, P. O., Adeyemi, A. A. & Ikyaagba, E. T. (2012). Forest structure analysis in the Oban Division of Cross River National Park, Nigeria. Journal of Agricultural Science and Technology B, 2(5), 510-518.

John, R., Dalling, J. W., Harms, K.. E., Yavitt , J. B., Stallard, R. F., Mirabello, M., Hubbell, S. P., Valencia, R., Navarrete, H. and Vallejo, O. (2007). Soil nutrients influence spatial distributions of tropical tree species. Proceedings of the National Academy of Sciences USA, 104, 864-869.

Johnson, O. M. & Marcellinus, A. H. (2013). The Nagi forest and need for protection. Journal of Research in Forestry, Wildlife and Environment, 7(2), 14-26.

Kessler, M., Keber, P. J. A., Gradstein, S. R., Bach, K., Schmull, M. & Pitopand, R. (2005). Tree diversity in primary forest and different land use systems in Central Sulawesi, Indonesia. Biodiversity and Conservation, 14, 547-560.

Kumar, A. & Ram, J. (2005). Anthropogenic disturbances and plant biodiversity in forests of Uttaranchal, Central Himalaya. Biodiversity Conservation, 14, 309-331.

Losose, C. & Leigh, G. (2004). Tropical Forest Diversity and Dynamism: Findings from a Large-Scale Plot Network. Chicago University Press, Chicago.

Lovejoy, T. E. (1997). Biodiversity: what is it? In: Reaka-Kudla et al., (Eds.) Biodiversity II: Understanding and Protecting our Natural Resources. Joseph Henry Press, Washington, D.C. 7-14Pp.

Lovette, J. C., Ruffo, C. K., Gereau, R. E. & Taplin, J. R. D. (2007). Field guide to the moist forest trees of Tanzania. Centre for Ecology Law and Policy Environment Department, University of York, United Kingdom. Available at: http://celp.org.uk/projects/tzforeco/.

Lu, X. T., Yin, J. X. & Tang, J. W. (2010). Structure, tree species diversity and composition of tropical seasonal rainforests in Xishuangbanna, south-west China. Journal of Tropical Forest Science, 22, 260-270.

Mace, G. M. , Collar, N. J., Gaston, K. J., Hilton-Taylor, C., Akcakaya, H. R., Leader-Williams, N., Milner-Gulland, E. J. & Stuart, S. N. (2008). Quantification of extinction risk: IUCN’s system for classifying threatened species. Conservation Biology, 22(6), 1424-1442.

Magnussen, S., Smith, B., Kleinn, C. & Sun, I. F. (2010). An urn model for species richness estimation in quadrat sampling from fixed-area populations. Forestry, 83, 293-305.

Maharjan, S. K., Poorter, L., Holmgren, M., Bongers, F., Wieringa, J. J. & Hawthorne, W. D. (2011). Plant functional traits and the distribution of West African rainforest trees along the rainfall gradient. Biotropica, 43, 552-561.

Mani, S. & Parthasarathy, N. (2005). Biodiversity assessment of trees in five inland tropical dry evergreen forests of Peninsular India. Systematics and Biodiversity, 3(1), 1-12.

Marisol, T., Lourens, P., Marielos Pen, C., Alfredo, A., Julio, B., Claudio, L., Juan Carlos, L., Oscar, L., Vincent, V., Pieter, Z. & Frans, B. (2011). Climate is a stronger driver of tree and forest growth rates than soil and disturbance. Journal of Ecology, 99, 254-264.

Muhammad, N. D. & Sa’adu, M. A. (2017). Conservation status of Vegetation in the Dryland of Northwestern Nigeria. International Journal of Agriculture, Forestry and Fisheries, 5(2), 18-24.

Musharaf, K., Farrukh, H. & Shahana, M. (2013). Conservation status of trees in Tehsil Takht-e-Nasratti, Karak Pakistan. African Journal of Plant Science, 7(6), 201-207.

Naidu, M. T. & Kumar, O. A. (2016). Tree diversity, stand structure, and community composition of tropical forests in Eastern Ghats of Andhra Pradesh, India. Journal of Asia Pacific Biodiversity, 9, 328-334.

Nath, O. C., Arunachalam, A., Khan, M. I., Arunachalam, K. & Barhuiya, A. R. (2005). Vegetation analysis and tree population structure of tropical wet evergreen forest in Namdapha National Park, Northeast India. Biodiversity and Conservation, 14, 2109-2136.

NEST (1991). Nigeria’s threatened environment; A national profile. Intec Printers Limited, Ibadan, 124-131Pp.

Nguyen, A., Pasquier, P. & Marcotte, D. (2015). Influence of ground water flow in fractured aquifers on standing column wells performance. Geothermics, 58, 39-48.

NIMET (2015). National weather forecasting and climate research. Agrometeorological Bulletin, 36 (3), 21-31.

Nsor, M. E. (2004). The geology of the Cross River Basin. Unpublished M.Sc. Thesis. Department of Soil Science, University of Calabar, Nigeria, 98Pp.

Odebiyi, J. A., Bada, S. O., Awodoyin, R. O., Oni, P. I. & Omoloye, A. A. (2004). Population structure of Vitelaria paradoxa Gaertn. F. and Parkia biglobosa (Jacq.) Benth. in the Agroforestry Parklands of Nigeria Humid Savannah. West Africa Journal of Applied Ecology, 5, 31-39.

Ogunjemite, B. G. (2015). Assessment of floristic composition of Ologbo Concession, Edo State, Nigeria, for conservation planning. Revue Scientifique et Technique Forêt et Environnement du Bassin du Congo, 4, 10-19.

Ogunjobi, J. A., Meduna, A. J., Oni, S. O., Inah, E. I. & Enya, D. A. (2010). Protection of staff’s job perception in Cross River National Park, Southern Nigeria. Middle East Journal of Scientific Research, 5(1), 22-27.

Ogunleye, A. J., Adeola, A. O., Ojo, L. O. & Aduradola, A. M. (2004). Impact of farming

Ojo, L. O. (2004). The fate of a tropical rainforest in Nigeria; Abeku sector of Omo Forest Reserve. Global Nest: The International Journal, 6(2), 116-130.

Olajide, O. (2004). Growth performance of trees in Akure Forest Reserve, Ondo State, Nigeria. Ph.D Thesis, University of Ibadan, Nigeria.

Omorogbe, R. U. (2004). Status of flora biodiversity and exploitation of biological resources in Sakponba Forest Reserve, Edo State. M.Sc Thesis, Ambrose Alli University Ekpoma, Edo State, 133Pp.

Oni, Y. M., Onyekwelu, J. & Ajibufun, I. A. (2010). The impact of climate change on forest resources. In: Onyekwelu, J., Adekunle, V. A. J. and Oke, D. O. (eds.). Proceedings of the 2nd Biennial National Conference of Forest Products Society of Nigeria held at Federal University of Technology, Akure, Nigeria on 26-29th April, 132-135Pp.

Onyekwelu, J. C., Mosandl, R. & Stimm, B. (2008). Tree species diversity and soil status of primary and degraded tropical rainforest ecosystems in South-Western Nigeria. Journal of Tropical Forest Science, 20(3), 193-204.

Pausas, J. G. & Austin, M. P. (2001). Patterns of plant species richness relation to different environments: An appraisal. Journal of Vegetation Science, 12, 153-166.

Petchay, O. L. & Gaston, K. J. (2002). Functional diversity (FD), species richness and community composition. Ecology Letters, 5(3), 402-411.

Philip, F. (Jr)., Oluyemi, A. A., Tokunbo, O., Charles, O. N., Sammy, U. U. & Edet, U. H. (2014). Forest resources of Cross River State: their potentials, threats and mitigation measures. IOSR Journal of Environmental Science, Toxicology and Food Technology, 8(6), 64-71.

Rajkumar, M. & Parthasarathy, N. (2008). Tree diversity and structure of Andaman giant evergreen forests in India. Taiwania, 53, 356-368.

Rodrigues, A. S. L., Pilgrim, J. D., Lamourex, J. F., Hoffmann, M. & Brooks, T. M. (2006). The value of the IUCN Red List for conservation. Trends in Ecology and Evolution, 21(2), 71-76.

Rowe, R. J. (2009). Environmental and geometric drivers of small mammal diversity along elevational gradients in Utah. Ecography, 32, 411–422.

Sabiiti, E. N. & Cobbina, J. (1992). Parkia biglobosa: a potential multipurpose fodder tree legume in West Africa. The International Tree Crops Journal, 7, 113-139.

Saka, M. G., Jatau, D. F. & Olaniyi, W. A. (2013). Status of indigenous tree species in Girei forest reserve of Adamawa state. Journal of Research in Forestry, Wildlife and Environment, 5(1), 28-40.

Sale, F. A., Samuel, D. & Ayo-Odifin, O. S. (2008). Effects of climate change on biodiversity. In: Popoola, L. (ed.). Proceedings of the 32nd Annual Conference of the Forestry association of Nigeria (FAN) held at Umuahia, Abia State on 20-24th October, 202-207Pp.

Sanwo, S. K., Ige, P. O., Sosanya, O. S. & Ogunlaye, O. G. (2015). Tree species diversity and forest stand dynamics in a tropical rainforest in Southern Nigeria. Malaysian Journal of Applied Biology, 44(2), 65-73.

Sarvade, S., Gupta, B. & Singh, M. (2016) Composition, diversity and distribution of tree species in response to changing soil properties with increasing distance from water source - a case study of Gobind Sagar Reservoir in India. Journal of Mt Science, 13, 522-533.

Schmitt K. (1990). Zoological survey of the Oban division of Cross River National Park. Oban Hill programme, Calabar, 21Pp.

Schmitt, C. B., Burgess, N. D., Coad, L., Belokurov, A., Besançon, C., Boisrobert, L., Campbell, A., Fish, L., Gliddon, D., Humphries, K., Kapos, V., Loucks, C., Lysenko, I., Miles, L.,. Mill, C., Minnemeyer, S., Pistorius, T., Ravilious, C., Steininger, M. & Winkel, G. (2009). Global analysis of the protection status of the world’s forests. Biological Conservation, 142(10), 2122-2130.

Shao, M. (2002). Parkia biglobosa. Changes in resources allocated in Kandiga, Ghana. Master Thesis, Michigan Technologist University, United State of America.

Shivaprasad, P. V., Vasanthraj, B. K. & Chandrashekar, K. R. (2002). Studies on the structure of Pilarkan reserve forest, Udupi District of Karnastaka. Journal of Tropical Forest Science, 14, 71-81.

Singh, J. S. (2002). The biodiversity crises: a multifaceted review. Current Science, 82, 638-647.

Small, A., Martin, T. G., Kitching, R. L. & Wong, K. M. (2004). Contribution of tree species to the biodiversity of a 1ha Old World rainforest in Brunei, Borneo. Biodiversity and Conservation, 13, 2067-2088.

Sobuj, N. A. & Rahman, M. (2011). Assessment of plant diversity in Khadimnnagar National Park of Bangladesh. International Journal of Environmental Science, 2(1), 1-13.

Soladoye, M. O., Sonibare, M. A., Nadi, A. O. & Alabi, D. A. (2005). Indigenous species producing valuable forest products in two sacred forests in South Eastern Nigeria. ARPN Journal of Science and Technology, 3(4), 415-421.

Sundarapandian, S. M. & Swamy, P. S. (2000). Forest ecosystem structure and composition along an altitudinal gradient in Western Ghats, South India. Journal of Tropical Forest Science, 1, 104-123.

ter Steege, H., Pitman, N. C., Phillips, O. L., Chave, J., Sabatier, D., Duque, A., Molino, J. F., Prevost, M. F., Spichiger, R. & Castellanos, H. (2006). Continental-scale patterns of canopy tree composition and function across Amazonia. Nature, 443, 444-447.

Tilk, M., Tullus, T. & Ots, K. (2017). Effects of environmental factors on the species richness, composition and community horizontal structure of vascular plants in Scots pine forests on fixed sand dunes. Silva Fenn, 1, 2.

Toledo, M., Pena-Claros, M., Bongers, F., Alarcon, A., Balcazar, J., Chuvina, J., Leano, C., Licona, J. C. & Poorter, L. (2012). Distribution patterns of tropical woody species in response to climatic and edaphic gradients. Journal of Ecology, 100, 253-263.

Toledo, M., Poorter, L., Pena-Claros, M., Alarcon, A., Balcazar, J., Chuvina, J., Leano, C., Licona, J. C., ter Steege, H. & Bongers, F. (2011). Patterns and determinants of floristic variation across lowland forests of Bolivia. Biotropica, 43, 405-413.

Tuomisto, H. (2010). A consistent terminology for quatifying species diversity? Yes it does exist. Oecologia, 4, 853-860.

Turner, I. M. (2001). The ecology of trees in the tropical rainforest. Cambridge University Press, Cambridge, 298Pp.

Udo, E. S., Olajide, O. & Udoh, E. A. (2009). Life-form classification and density of plants producing economically valuable non-timber products in Ukpon Community Forest, Akwa Ibom State, Nigeria. Nigerian Journal of Botany, 22(1), 147-154.

UNEP (2007). Global Environment Outlook 4. United Nations Environment Programme, Nairobi.

Vahdati, F. B., Mehrvarz, S. S., Dey, D. C. & Naqinezhad, A. (2017). Environmental factors–ecological species group relationships in the Surash lowland-mountain forests in Northern Iran. Nord Journal of Botany, 35, 240-250.

Varshney, A. & Anis, M. (2014). Trees: Propagation and Conservation Biotechnological Approaches for Propagation of a Multipurpose Tree, Balanites aegyptiaca Del. Springer New Delhi, Dordrecht Heidelberg London, New York, 116Pp.

Vasanthraj, B. K. & Chandrashekar, K. R. (2006). Analysis of the structure of Charmady reserve forest. Tropical Ecology, 47(2), 279-290.

Vasanthraj, B. K., Shivaprasad, P. V. & Chandrashakar, K. K. (2004). Studies on the structure of Jadkal forest, Udupi District, India. Journal of Tropical Science, 17, 13-22.

Vie, J. C., Hilton-Taylor, C., Pollock, C., Ragle, J., Smart, J., Stuart, S. N. & Tong, R. (2008). The IUCN Red List: a key tool. In: J. C. Vie, C. Hilton-Taylor & S. N. Stuart (eds.). The 2008 Review of the IUCN Red List of Thraetened Species. IUCN Gland, Switzerland.

Wakawa, L., Suleiman, A., Ibrahim, Y. & Adam, L. (2017). Tree species biodiversity of a Sahelian ecosystem in Noertheast Nigeria. Journal of Bartin Faculty of Forestry, 19(2), 166-173.

WCMC (1998). Brachystegia nigerica. The IUCN RED List of Threatened Species. Available at: www.10.2305 /IUCN.UK.1998RLTS.T32712A9724132.en.

WCS (2012). Nigeria program conservation strategy, 2012-2016, Wildlife Conservation Society, 123Pp.

WWF (2010). The Amazon rainforest. WWF, U. S. Geological Survey, ICTA, TNC, University of Kassel.

Yang, K. C., Lin, .J. K., Hsieh, C. F., Huang, C. L., Chang, Y. M., Kuan, L. H. Su, J. F. & Chiu, S. T. (2008). Vegetation pattern and woody species composition of a broad-leaved forest at the upstream basin of Nantzuhsienhsi in mid-southern Taiwan. Taiwania, 53, 325-337.

Young, S. & Swiacki, L. N. (2006). Surveying the forest biodiversity of Evansburg State Park: Plant community classification and species diversity assessment. International Journal of Botany, 2(3), 293-299.

Zakaluk, R. & Sri Ranjan, R. (2008). Predicting the leaf water potential of potato plants using RGB reflectance. Canadian Biosystems Engineering, 50, 7.1 – 7.12.

Zhang, C. S., Li, X. Y., Chen, L., Xie, G. D., Liu, C. L. & Pei, S. (2016). Effects of topographical and edaphic factors on tree community structure and diversity of subtropical mountain forests in the Lower Lancang River Basin. Forests, 7, 222.

Zhang, X. P., Wang, M. B., She, B. & Xiao, Y. (2006). Quantitative classification and ordination of forest communities in Pangquangou National Nature Reserve. Acta Ecologica Sinica, 26, 754-761.

Zhao, L. J., Xiang, W. H., Li, J. X., Lei, P. F., Deng, X. W., Fang, X. & Peng, C. H. (2015). Effects of topographic and soil factors on woody species assembly in a Chinese Subtropical Evergreen Broadleaved Forest. Forests, 6, 650-669.




How to Cite

Akwaji, P. I., Oden, G. N., Onah, D. O., Okon, E. I., Ajikah, L. B., & Akomaye, F. A. (2022). Diversity, distribution, and conservation status of forest tree species in cross river state, Nigeria. Sustainability and Biodiversity Conservation, 1(1), 42–83. https://doi.org/10.5281/zenodo.7135046