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Distribution of tree species along a gallery forest–savanna gradient: patterns, overlaps and ecological thresholds

  • Akomian Fortuné Azihou (a1), Romain Glèlè Kakaï (a1), Ronald Bellefontaine (a2) and Brice Sinsin (a1)


Savannas intermingled with gallery forests are dynamic habitats typical in Africa. This study aims to determine if differences in species traits lead to non-overlapping distribution of gallery-forest and savanna species and abrupt transition between gallery forest and savanna. Tree species densities were measured in 375 plots of 1500 m2 covering a total sample area of 56.25 ha along forty 3-km transects located at right angles to a riverbed with gallery forest into surrounding savanna. Location, vegetation type, soil physical properties, erosion and fire occurrence were recorded as site factors. Data analysis included the quantification of co-occurrence patterns, threshold indicator taxa analysis and fuzzy set ordination. The gallery forest–savanna gradient predicted floristic composition of plots with a correlation of 0.595 but its accuracy was locally modified by the occurrence of fire and the physical properties of soil that covered more than 30% of the range of residuals. The distribution of gallery-forest and savanna tree species did not overlap. Along the gallery forest–savanna gradient, savanna species gradually increased in density while gallery-forest species showed a community threshold at 120 m from the river beyond the width of gallery forest. The forest species driving this trend should play an important role in the dynamics of gallery forest–savanna boundaries.


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AKOEGNINOU, A., VAN DER BURG, W. J., VAN DER MAESEN, L. J. G., ADJAKIDJE, V., ESSOU, J. P., SINSIN, B. & YEDOMONHAN, H. 2006. Flore analytique du Bénin. Wageningen University Papers 06.2:11034.
ASH, J. 1988. The location and stability of rainforest boundaries in north-eastern Queensland, Australia. Journal of Biogeography 15:619630.
ASKEW, G. P., MOFFATT, D. J., MONTGOMERY, R. F. & SEARL, P. L. 1970. Interrelationships of soils and vegetation in the savanna–forest boundary zone of north-eastern Mato Grosso. The Geographical Journal 136:370376.
ASNER, G. P., ELMORE, A. J., OLANDER, L. P., MARTIN, R. E. & HARRIS, A. T. 2004. Grazing systems, ecosystem responses, and global change. Annual Review of Environment and Resources 29:261299.
BAKER, M. E. & KING, R. S. 2010. A new method for detecting and interpreting biodiversity and ecological community thresholds. Methods in Ecology and Evolution 1:2537.
BAKKER, J. D. 2008. Increasing the utility of indicator species analysis. Journal of Applied Ecology 45:18291835.
BANFAI, D. S. & BOWMAN, D. 2007. Drivers of rain-forest boundary dynamics in Kakadu National Park, northern Australia: a field assessment. Journal of Tropical Ecology 23:7386.
BOND, W. J. 2008. What limits trees in C4 grasslands and savannas? Annual Review of Ecology, Evolution and Systematics 39:641659.
BOND, W. J., MIDGLEY, G. F. & WOODWARD, W. I. 2003. The importance of low atmospheric CO2 and fire in promoting the spread of grasslands and savannas. Global Change Biology 9:973982.
BOWMAN, D. M. J. S. 2000. Australian rainforests: islands of green in a sea of fire. Cambridge University Press, Cambridge. 357 pp.
BOWMAN, D. M. J. S. & PANTON, W. J. 1993. Factors that control monsoon-rainforest seedling establishment and growth in north Australian Eucalyptus savanna. Journal of Ecology 81:297304.
BRAITHWAITE, N. T. & MALLIK, A. U. 2012. Edge effects of wildfire and riparian buffers along boreal forest streams. Journal of Applied Ecology 49:192201.
COCHRANE, M. A. 2003. Fire science for rainforests. Nature 421:913919.
COLLIN, A., BERNARDIN, D. & SERO-GUILLAUME, O. 2011. A physical-based cellular automaton model for forest-fire propagation. Combustion Science and Technology 183:347369.
DELVINGT, W., HEYMANS, J. C. & SINSIN, B. 1989. Guide du Parc National de la Pendjari. CECA-CEE-CEA, Brussels. 125 pp.
DUFRÊNE, M. & LEGENDRE, P. 1997. Species assemblages and indicator species: the need for a flexible asymmetrical approach. Ecological Monographs 67:345366.
FORTIN, M. J., KEITT, T. H., MAURER, B. A., TAPER, M. L., KAUFMAN, D. M. & BLACKBURN, T. M. 2005. Species’ geographic ranges and distributional limits: pattern analysis and statistical issues. Oikos 108:717.
FURLEY, P. A. 1999. The nature and diversity of neotropical savanna vegetation with particular reference to the Brazilian cerrados. Global Ecology and Biogeography 8:223241.
GEIGER, E. L., GOTSCH, S. G., DAMASCO, G., HARIDASAN, M., FRANCO, A. C. & HOFFMANN, W. A. 2011. Distinct roles of savanna and forest tree species in regeneration under fire suppression in a Brazilian savanna. Journal of Vegetation Science 22:312321.
GIGNOUX, J., LAHOREAU, G., JULLIARD, R. & BAROT, S. 2009. Establishment and early persistence of tree seedlings in an annually burned savanna. Journal of Ecology 97:484495.
GILPIN, M. E. & DIAMOND, J. M. 1982. Factors contributing to non-randomness in species co-occurrences on islands. Oecologia 52:7584.
GOOD, S. P. & CAYLOR, K. K. 2011. Climatological determinants of woody cover in Africa. Proceedings of the National Academy of Sciences, USA 108:49024907.
HENNENBERG, K., GOETZE, D., KOUAME, L., ORTHMANN, B. & POREMBSKI, S. 2005. Border and ecotone detection by vegetation composition along forest–savanna transects in Ivory Coast. Journal of Vegetation Science 16:301310.
HIGGINS, S. I., BOND, W. J., FEBRUARY, E. C., BRONN, A., EUSTON-BROWN, D. I. W., ENSLIN, B., GOVENDER, N., RADEMAN, L., O'REGAN, S., POTGIETER, A. L. F., SCHEITER, S., SOWRY, R., TROLLOPE, L. & TROLLOPE, W. S. W. 2007. Effects of four decades of fire manipulation on woody vegetation structure in savanna. Ecology 88:11191125.
HIROTA, M., NOBRE, C., OYAMA, M. D. & BUSTAMANTE, M. M. C. 2010. The climatic sensitivity of the forest, savanna and forest–savanna transition in tropical South America. New Phytologist 187:707719.
HOFFMANN, W. A. & FRANCO, A. C. 2003. Comparative growth analysis of tropical forest and savanna woody plants using phylogenetically-independent contrasts. Journal of Ecology 91:475484.
HOFFMANN, W. A., ORTHEN, B. & FRANCO, A. C. 2004. Constraints to seedling success of savanna and forest trees across the savanna–forest boundary. Oecologia 140:252260.
HOFFMANN, W. A., ADASME, R., HARIDASAN, M., CARVALHO, M., GEIGER, E. L., PEREIRA, M. A. B., GOTSCH, S. G. & FRANCO, A. C. 2009. Tree topkill, not mortality, governs the dynamics of alternate stable states at savanna–forest boundaries under frequent fire in central Brazil. Ecology 90:13261337.
HOFFMANN, W. A., JACONIS, S. Y., MCKINLEY, K. L., GEIGER, E. L., GOTSCH, S. G. & FRANCO, A. C. 2012a. Fuels or microclimate? Understanding the drivers of fire feedbacks at savanna–forest boundaries. Austral Ecology 37:634643.
HOFFMANN, W. A., GEIGER, E. L., GOTSCH, S. G., ROSSATTO, D. R., SILVA, L. C. R., LAU, O. L., HARIDASAN, M. & FRANCO, A. C. 2012b. Ecological thresholds at the savanna–forest boundary: how plant traits, resources and fire govern the distribution of tropical biomes. Ecology Letters 15:759768.
HOLDO, R. M. 2005. Stem mortality following fire in Kalahari sand vegetation: effects of frost, prior damage, and tree neighbourhoods. Plant Ecology 180:7786.
HOLDO, R. M., HOLT, R. D. & FRYXELL, J. M. 2009. Grazers, browsers, and fire influence the extent and spatial pattern of tree cover in the Serengeti. Ecological Applications 19:95109.
KELLMAN, M. 1984. Synergistic relationships between fire and low soil fertility in neotropical savannas: a hypothesis. Biotropica 16:158160.
LLOYD, J., BIRD, M. I., VELLEN, L., MIRANDA, A. C., VEENENDAAL, E. M., DJAGBLETEY, G., MIRANDA, H. S., COOK, G. & FARQUHAR, G. D. 2008. Contributions of woody and herbaceous vegetation to tropical savanna ecosystem productivity: a quasi-global estimate. Tree Physiology 28:451468.
MAGURRAN, A. E. & HENDERSON, P. A. 2003. Explaining the excess of rare species in natural species abundance distributions. Nature 422:714716.
MIDGLEY, J. J., LAWES, M. J. & CHAMAILLE-JAMMES, S. 2010. Savanna woody plant dynamics: the role of fire and herbivory, separately and synergistically. Australian Journal of Botany 58:111.
MURPHY, B. P. & BOWMAN, D. M. J. S. 2012. What controls the distribution of tropical forest and savanna? Ecology Letters 15:748758.
NANGENDO, G., TER STEEGE, H. & BONGERS, F. 2006. Composition of woody species in a dynamic forest-woodland -savanna mosaic in Uganda: implications for conservation and management. Biodiversity and Conservation 15:14671495.
NATTA, A. K. 2000. Tree species diversity assessment in riparian forests using remote sensing, geographic information systems and geostatistics (case study of Toui-Kilibo protected forest in Benin). M.Sc. thesis, ITC Forest Science Division, Enschede. 91 pp.
PAG2. 2005. Plan d'aménagement participatif et de gestion 2004–2013. Parc National de la Pendjari, Bénin. 83 pp.
RATNAM, J., BOND, W. J., FENSHAM, R. J., HOFFMANN, W. A., ARCHIBALD, S., LEHMANN, C. E. R., ANDERSON, M. T., HIGGINS, S. I. & SANKARAN, M. 2011. When is a ‘forest’ a savanna, and why does it matter? Global Ecology and Biogeography 20:653660.
RAY, D., NEPSTAD, D. & MOUTINHO, P. 2005. Micrometeorological and canopy controls of fire susceptibility in a forested Amazon landscape. Ecological Applications 15:16641678.
ROBERTS, D. W. 1986. Ordination on the basis of fuzzy set theory. Vegetatio 66:123131.
RUSSELL-SMITH, J., STANTON, P. J., WHITEHEAD, P. J. & EDWARDS, A. 2004. Rain forest invasion of eucalypt-dominated woodland savanna, Iron Range, north-eastern Australia: I. Successional processes. Journal of Biogeography 31:12931303.
SCHRÖDER, A., PERSSON, L. & DE ROOS, A. M. 2005. Direct experimental evidence for alternative stable states: a review. Oikos 110:319.
SOKPON, N., AFFOUKOU, M., AMAHOWE, I., GANDJI, L., GNONLONFIN, L. & SOSSOU, B. 2008. Dynamique spatio-temporelle des formations végétales du Complexe Parc National de la Pendjari, zones cynégétiques de la Pendjari et de l'Atacora. Laboratoire d'études et de recherches forestières, FA/UP/République du Bénin. 59 pp.
STAVER, A. C., ARCHIBALD, S. & LEVIN, S. A. 2011. The global extent and determinants of savanna and forest as alternative biome states. Science 334:230232.
STEVENS, J. T. & BECKAGE, B. 2009. Fire feedbacks facilitate invasion of pine savannas by Brazilian pepper (Schinus terebinthifolius). New Phytologist 184:365375.
SWAINE, M. D., HAWTHORNE, W. P. & ORGLE, T. K. 1992. The effects of fire exclusion on savanna vegetation at Kpong, Ghana. Biotropica 24:166172.
WHITE, F. 1983. The vegetation of Africa: a descriptive memoir to accompany the UNESCO/AETFAT/UNSO vegetation map of Africa. Natural Resources Research Report XX. UNESCO, Paris. 356 pp.
ZACHARIAS, M. A. & ROFF, J. C. 2001. Use of focal species in marine conservation and management: a review and critique. Aquatic Conservation: Marine and Freshwater Ecosystems 11:5976.
ZUUR, A. F., IENO, E. N. & ELPHICK, C. S. 2010. A protocol for data exploration to avoid common statistical problems. Methods in Ecology and Evolution 1:112.



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