Most tile bonuses were +3 or +2, with +1 to adjacent, but that is not always the case, as there ere are 2 exceptions.
 
   Research:  wasn't one of these +3?
   Rare Earth:  +2 research, +1 Manufacturing
   Mineral Rich:  +2 research, +1 Wealth
 
   Population:  why is one of these a +1 and not a +2?
   Wild Grain:  +3 population, +1 Approval
   Floodplain:  +1 Population, +1 Wealth