The first large scale forest dynamics plot in Madagascar was set up at the Ankarafantsika National Park in northwestern part of Madagascar from 2019 to 2020. The total area of the plot is 15 ha (500 m×300 m) in seasonal dry forests, 42,420 trees (DBH > 5 cm) were measured and 168 tree species including 23 liana species in 61 families were identified. Despite the severe dry season on this plateau of well-drained sandy soil, the relative rich diversity than we expect before, may be caused that Ankarafantsika located in the transition zone between the northern area of tropical rain and the southwestern area of dry forest. The north-western part seems to be related to Africa continent geographically and ethnically, and some African species are invading to this area. Some foreign species used for environmental reforestation are also invading to the site. There are several endemic species that can only be found here and species that are taken as type specimens. In particular, the genus Karomia of Lamiaceae, may be the distribution centre. Also some species which are distributed in pan-Madagascar were seen despite their many differences in environment.