Moist lower montane rainforest classification: a case study from Bwindi Impenetrable National Park, Uganda Tomas Chaigneau 1 , Antje Ahrends 1,2 , Jennifer Argent 1 , Naboon Riddhiraska 1 and Rob Marchant 1 * 1 York Institute for Tropical Ecosystem Dynamics (KITE), Environment Department, University of York, Heslington, York, YO10 5DD, U.K. and 2 Royal Botanic Gardens Edinburgh, 20A Inverleith Row, Edinburgh CB2 3EJ, U.K. Abstract Moist lower montane vegetation has rarely been classified beyond broad zonational belts over large altitudinal ranges due to highly diverse species composition and structure. This study shows it is possible to further classify such forest types within Bwindi-Impenetrable National Park (BINP), and that these assemblages can be explained by a combi- nation of environmental conditions and past management. Botanical and environmental data were collected along some 4000 m of linear transects from the area surround- ing Mubwindi Swamp, BINP. Ordination using Nonmetric Multidimensional Scaling (NMDS) and classification using Two-way Indicator Species Analysis (TWINSPAN) suc- cessfully identified four different species assemblages. These forest types were then named on the basis of the ecological characteristics of the species within the group, and the environmental conditions influencing the distribution and past disturbance of the forest. The techniques used were in agreement for three out of the four forest types identified. Analysis using an environmental overlay showed a sig- nificant association between forest type and altitude. The results of this study indicate that a regional classification of forest types within moist lower montane forest belt using only tree species is possible, and that the forest types identified can be explained by environmental conditions and past management. Key words: Afromontane forest, altitudinal gradient, Bwindi Impenetrable Forest, classification Re ´sume ´ La ve ´ge ´tation humide de basse montagne a rarement e ´te ´ classe ´e au-dela ` de larges ceintures de zonage portant sur des e ´tendues de grandes amplitudes altitudinales, en raison de compositions et de structures d’espe `ces extre ˆmement diverses. Cette e ´tude montre qu’il est possible de classer plus pre ´cise ´ment de tels types forestiers dans le Parc National de la Fore ˆt Impe ´ne ´trable de Bwindi (BINP), et que l’on peut expliquer ces assemblages par une combinaison de conditions environnementales et de gestion passe ´e. Des donne ´es botaniques et environnementales ont e ´te ´ collect- e ´es le long de quelque 4,000 m de transects line ´aires a ` partir de la zone entourant le Marais de Mubwindi, au BINP. L’ordination par la Gradation non me ´trique multi- dimensionnelle et la classification utilisant l’Analyse TWINSPAN (Two-way Indicator Species Analysis) ont re ´ussi a ` identifier quatre assemblages d’espe `ces diffe ´rents. Ces types forestiers furent alors nomme ´s en se basant sur les caracte ´ristiques e ´cologiques des espe `ces au sein du groupe ainsi que sur les conditions environnementales qui influ- encent la distribution et des perturbations anciennes des fore ˆts. Les techniques utilise ´es se sont montre ´es cohe ´rentes pour trois des quatre types de fore ˆt identifie ´s. L’analyse utilisant une superposition environnementale a re ´ve ´le ´ une association significative entre type forestier et altitude. Les re ´sultats de cette e ´tude indiquent qu’une classification re ´gionale des types forestiers dans la ceinture forestie `re humide qui entoure la basse montagne est possible en n’utilisant que trois espe `ces d’arbres, et que les types forestiers identifie ´s peuvent s’expliquer par les conditions environnementales et par la gestion ante ´rieure. Introduction Bwindi-Impenetrable National Park (BINP) is situated in the Kigezi (Rukiga) Highlands of South Western Uganda at approximately 0°53¢ to 1°08¢S by 29°35¢ to 29°50¢E (United Nations Environment Programme, UNEP, 2003) *Correspondence: E-mail: rm524@york.ac.uk Ó 2009 The Authors. Journal compilation Ó 2009 Blackwell Publishing Ltd, Afr. J. Ecol., 48, 807–815 807