Any linkage between ethnicity and conflict resolution is more a product of culture than of ethnicity per se. Certainly, there can be considerable overlap between the two, but a stronger argument can be made of a linkage involving culture than of ethnicity.
Different cultures, which may have evolved over hundreds or thousands of years, shape perceptions and establish customs that have a direct bearing on conflict resolution. Because there is an overlap between culture and ethnicity -- for example, attitudes toward conflict resolution in a sub-Saharan African community or in an ancient Islamic civilization would invariably be a product of both ethnicity and culture -- that convergence would most certainly shape approaches to conflict resolution.
When the United States becomes involved in an overseas conflict, Iraq and Afghanistan are certainly two good examples, it generally finds itself experiencing enormous difficulties in resolving conflicts not just between it and and nationals of the foreign country in question, but also between the disparate tribes and clans that predominate in those regions of the world. Different clans may have customs that involve resolving conflicts through means not entirely consistent with American values, for example, stoning alleged adulterers or cutting off the limbs of offending indivduals. Those are age-old methods of conflict resolution with which we often struggle in attempting to mediate disputes in foreign lands.