ABSTRACT
Ectomycorrhizal fungal community is largely integrated into the overall diversity and ecosystem processes. This study aims to determine the below-ground structure of ectomycorrhizal fungi community associated with Uapaca bojeri and Sarcolaena oblongifolia in highland sclerophyllous forest of Madagascar and to assess the impact of shared ectomycorrhizal symbiont on tree seedling recruitment and plant succession facilitation. Ectomycorrhizal fungi were identified based on morphotyping and RFLP analysis of rDNA internal transcribed spacer (ITS)-large subunit followed by sequence analysis of each RFLP pattern. Impacts of shared ectomycorrhizal symbionts on seedling development of U. bojeri were investigated in soil microcosm collected at different distances from naturally established of both host plant species. The ECM fungal communities associated with both plants showed high similarity and were dominated by the genus Russula. Expressed as RFLP types, 21 taxa of ECM fungi were collected from root tips. More than half of these ECM taxa were shared between the two plant species. The better development of U. bojeri seedling was observed in soil samples naturally influenced by S. oblongifolia and located between 5 and 10 m from established U. bojeri where seedlings were colonized particularly by shared ectomycorrhizal symbionts. This study demonstrates that natural establishment of secondary colonizing hosts may contribute to tree seedling recruitment and development by providing compatible ectomycorrhizal symbionts.

Keywords: Below-ground ectomycorrhizal community, secondary successional processes, facilitation, ITS- RFLP, Madagascar.