Ohia trees are dying rapidly, Why?

[terracore]

On one of our lots where we have poor soil there is an ohia "dead zone" around an outcropping of albezia trees. The ferns etc still grow but all the ohia are dead. I don't think its a matter of the albezia canopy shading the ohia because the dead zone extends beyond the canopy. The albezia have an impressive root system, I'm wondering if they are leeching all the nutrients from the scarce soil leaving the ohia unable to fend off other problems. I recently started killing the albezia, but it will take many years to find out if it makes any difference.