Stand structure and species co-occurrence in mixed and monodominant Central African tropical forests

Abstract: We compare forests dominated by Gilbertiodendron dewevrei at the Dja Biosphere Reserve (Cameroon) with adjacent high-diversity mixed forests in terms of tree-species composition and stand structure, in order to understand the co-occurrence of mixed forest tree species in the monodominant forest. A total of 18 1-ha permanent plots were established in the two forest types. In each plot, all trees with dbh ≥10 cm were identified as were those <10 cm dbh within a subsample of 300 m 2 . Species richness was significantly different between the two forest types. Mixed forest had an average of 109 species ha −1 for trees ≥10 cm dbh and 137 species for trees <10 cm dbh. By contrast, G. dewevrei -dominated forest had an average of 47 species ha −1 (≥10 cm dbh) and 92 species (<10 cm dbh). There was no significant difference in terms of stem density of the trees with dbh <10 cm between the two forests (mixed: 3.7 stems m −2 ; monodominant: 3.1 stems m −2 ). As G. dewevrei is a shade-tolerant species that can regenerate under its own shade, its higher stem density and basal area can reduce species richness of an area.