Sampling strategy. (a) Original planting distances were 8 × 12 m (O = tree). Sampling was done in strips of 48 m in width and 250 to 1000 m in length. The length is depending on the presence of roads, rivers, savannah or secondary forest areas, encountered during the inventory. (b) Schematic view on the number of samples for the different variables. Boxes with subsamples originate from larger samples and are connected by lines.