Is insect vertical distribution in rainforests better explained by distance from the canopy top or distance from the ground?

The way arthropods are distributed vertically in tropical forests has been of great interest with diversity often greatest at or near the canopy top. Typically, stratification is measured up from the ground but, since the height of trees reaching the canopy top can vary, we hypothesise that distance down from the canopy top, might better explain arthropod distributions. To test this samples were collected from Australian tropical rainforest...