Fig. 5

Flow-chart showing full decision tree structure of grain population model for classifying grains. Numbered diamonds represent filters (filter contents are tabulated in Additional file 1: B). Coloured rectangles represent grain populations described in Table 3. Arrows indicate flow direction of connectors between nodes. Key shows assignment of populations to interpretive source/material categories listed in Table 2. Note, alphabetic labelling of populations reflects order in which these appear in decision tree and hence deviates from order in key