Scientific terms

While going through the Agrovoc Concept server,I found some terms are missing which were found in the earlier Agrovoc database (  Eg.common silver fir, Algerian fir). The use of the related term or Use / Use for the refining of the scientific terms/ common names is not yet clear. Is it better to refine the common names as Alternative descriptor or as the non descriptors (Use/UF) as both have the refinement of  is same as /correpond to or has scientific name / is scientific name. What difference does it make it to refine in the new tool?