Site description and location of direct measured trees in the Ankeniheny Zahamena forest corridor, Madagascar

A forest inventory was carried out within all sites of closed canopy in the four Zone Of Interest (ZOI). Name of species, DBH, and height (H) were recorded during the forest inventory. In order to have an idea of above-ground biomass (AGB) density, AGB at tree level was estimated by applying the allometric equation developed by Chave et al. 2014 on the inventory data. Indeed, the model developed by Chave et al. was considered because it was the most recent and included the existing national equations. Subsequently, total AGB at stand level (Mg.ha-1) for each site was calculated by summing the AGB values of all trees in the same site and dividing this value by the total survey area (ha) sampled. After, two (2) ZOIs were chosen according to the extreme values of AGB at stand level while considering the ease of access. In fact, ZOI3 has the highest value of AGB; ZOI1 and ZOI2 have very similar AGB values and have been the lowest. Thus, considering the accessibility and the cost of the work, ZOI2 was chosen for the direct measurement. The selection of sites was based on the AGB values per site in relation to the representativeness of each tree size (proportion of trees per DBH class). In order to establish this relation, AGB per site was divided at three class so that each class has the same number of values (a percentage at around 33% of the total number of sites for each class). The aim is to see for each site, which category of tree (in terms of DBH) contributes the most to its biomass (ABG). Afterwards, consideration of contribution of each tree size into AGB density in Mg.ha-1 per site for each ZOI, at least 3 sites for each ZOI were selected for BGB direct measurements. The choice of sites also takes account of the accessibility, any restriction in field process in relation with this protected area zonage. Target trees were chosen from the four dominant species sorted out from the forest inventory. Target trees were selected by considering the selection of zone, sites, diameter classes and species. Three categories of trees were considered, trees with DBH≥ 20cm, trees with 10≤DBH<20cm and trees with 5≤DBH<10cm. Following all these process, in total, 54 target trees were selected for direct measurements of BGB: 2 zones * 3 sites/zone * 3 species per site * 3 diameter class / species.