Lianas diversity, distribution patterns and functional ecology in a Central African tropical rain forest, Ituri, Democratic Republic of Congo

Project description
The Congo basin forest is the second world largest important forest after the Amazonian forest. More than 50 % of this forest lies in the Democratic Republic of Congo (DRC) and play key role for carbon sequestration and water regulation. In particular, Ituri Forest in the northeastern is one of the rare DRC’s remaining intact forests. This forest also has particularities of a single species canopy tree forming monodominant forest up to 100 sq. km that co-occur with a sister mixed forest, while within forest soil characteristics are relatively similar. But, community composition and structure significantly varies with canopy structure. Species differ in their tolerance to canopy features resulting in differentiating distribution patterns and their abundance. Although many studies focused on trees, lianas received almost no attention in the entire Central African rain forest. Much knowledge of central african forest lianas diversity comes from the published flora. No large-scale forest lianas inventory has been so far conducted in African rain forest. Thus, the role of lianas in foret ecosystem functioning also remains unclear by lack of reliable data and information.

My study is part of the Ituri Forest Dynamics Plot project and will deal with long-term dynamics of tropical forest lianas. The overall goals of the Ituri dynamics plots are to compare floristic composition of two mature forests that contiguously co-occur, and to explore their spatial and temporal changes. Data here used is based on four 10-ha permanent plots in the Ituri Forest, northeastern DR Congo, and covers nearly 25,000 individuals belonging to c. 260 species. Plots data sets (initial and two recencuses) of ~ 14 years with recensuses intervals of 5-6 years of growth, mortality and recruitment will be used for dynamic analysis. Although botanical data on lianas and trees exisit; liana infestation, tree crown illumination and crown form have not been evaluated, and the height has not been estimated. These additional information will be collected during this project. In addition, for each plot soil samples will be collected in the field and climatic data (precipitation, temperature) will be obtained from existing data sets and meteorological data that the Ituri Dynamics Plot project continues collecting in each of the field station of the present study.

In particular, questions of distribution patterns and diversity of lianas in relation to edaphic nutrient and habitat will be adressed.The plot data allow tests of key demographic rates for both common and rare, as well as understorey and canopy liana species. The change and stability of the liana component in a changing forest environment, will be examined through evaluation of lianas dynamic in terms of abundance, recruitment, growth and mortality of liana community in these forest. Species characteristics such as above-ground biomass accumulation, mortality and growth rate will be also addressed across the environmental gradients. Furthermore, the phylogenetic structure of the liana community will be explored.
Four hypotheses will be tested:
1) Are these forests undergoing directional change as a result of recent climatic shifts? 
2) Does the abundance or composition of lianas in these forests change due to long-term succession following other disturbances? 
3) Does the liana cover has a significant impact on tree growth within the plots? 
4) Do species distributions are shaped by species traits, and  how this forest ecosystem properties are in part determined by the functional traits of liana species that contribute in building the forest community.

This study forms a crucial contribution relevant to understanding the dynamics and functional ecology of natural liana populations. Results obtained will provide insight to the role of lianas in the forest and in a climate changing environment, based on reliable local site conditions data, ecosystem characteristics and species traits. They then, maximize the knowledge of liana species diversity, composition and structure within two distinguishing forest canopy structure. The research will also reveals the factors controlling the diversity, abundance, and distribution of liana species in forest communities considering both host-tree availability and soil component using a much larger dataset than previous studies.

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Project information

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News

• interview on Dutch Radio 1, Labyrint, 19 december 2010
• Corneille Ewango was 'Invited speaker' on the TEDGlobal 2007 Conference :Africa”:The Next Chapiter, held 3-4 June, 2007 in Arusha, Tanzania.

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Publications

• Ewango, C.E.N. (2010). The liana assemblage of a Congolian rainforest: Diversity, structure and dynamics. PhD thesis, Wageningen University, the Netherlands.ISBN 978-90-8585-813-3; 161 pp. With references, with summaries in English, Dutch and French
• Condit R; Ashton P; Bunyavejchewin S; Dattaraja HS; Davies S; Esufali S; Ewango C.E.N; Foster R; Gunatilleke IAUN; Gunatilleke CVS; Hall P; Harms KE; Hart T; Hernandez C; Hubbell S; Itoh A; Kiratiprayoon S; LaFrankie J; Loo de Lao S; Makana J-R; Supardi Noor MN; Abdul Rahman Kassim; Russo S; Sukumar R; Samper C; Suresh HS; Tan S; Thomas S; Valencia R; Vallejo M; Villa G. (2006). The importance of demographic niches to tree diversity. (Data from 14 large-scale monitoring plots demonstrate that demographic tradeoffs are not associated with local tree species richness). Science 313: 98-101.
• Gerwing.J.J.; Schnitzer, S.A.; Burnham, R.J.; Bongers, F.J.J.M.; Chave, J.; DeWalt, S.J.; Ewango, C.E.N.; Foster, R.; Kenfack, D.; Martinez-Ramos, M.; Parren, M.P.E.; Parthasarathy, N.; Pérez-Salicrup, D.R.; Putz, F.E.; Thomas, D.W. (2006) A standard protocol for liana censuses. Biotropica 38 (2): 256 – 261.
• Condit, R. et al (2005). Tropical tree a-diversity: Results from a worldwide network of large plots. Biol. Skr. 55: 565-582.
• Thomas, S. C., J. Makana, T. B. Hart, J. A. Hart, R. Condit; Ewango, C. E. N. (2005). Deterministic changes in species composition in primary forest in the Eastern Congo basin. Abstract. Ecological Society of America 90th Annual Meeting, 7–12 August 2005, Montreal Quebec, Canada. ESA, Washington, D.C., USA.
• Ashton, P.; CTFS Working Group (2004). Floristics and vegetation of the Forest Dynamics plots. In: Losos E.C. and Leigh, E.G. Jr. (eds.) Forest Diversity and Dynamism: Findings from a Large-Scale Plot Network. 90-102. University of Chicago Press, Chicago.
• Condit, C.: Leigh, E.G.Jr; Loo de Lao, S.; CTFS Working Group (2004). Species-Area relationships and diversity measures in the forest dynamics plots. In:  Losos, E.C. and Leigh, E.G. Jr. (eds). Forest Diversity and Dynamism: Findings from a Large-Scale Plot Network. 79-89. University of Chicago Press, Chicago.
• Losos, E.C.; CTFS Working Group (2004). The structure of tropical forests. In: Losos E.C. and Leigh, E.G. Jr. (eds). Forest Diversity and Dynamism: Findings from a Large-Scale Plot Network. 69-78. University of Chicago Press, Chicago.
• Makana, J-R; Hart, T.B.; Liengola, I.; Ewango, C. (2004). The Ituri Forest Dynamics Plots. In: E.C. Losos and E.G. Leigh, Jr. (eds.). Forest Diversity Dynamism: Findings from a Network of Large-scale Tropical Forest Plots, 492-505. The University of Chicago Press, Chicago.
• Makana, J-R; T.B. Hart; Ewango, C.E.N.; Liengola, I and Thomas, S.C. (2004). Tree demography and population change in the Ituri Forest Dynamics Plots, Democratic Republic of Congo. Inside CTFS, Summer 2004, PP. 5, 14.

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Links

• Wildlife Conservation Society (WCS)
• Center for Tropical Forest Science (CTFS) of the Smithsonian Tropical research Institute

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