Nitric acid acting as oxidising agent
The reactions of nitric acid could be due to 1) its acid nature, 2) its oxidizing properties, or both. 

Orthocresol was correct that the substrate could predetermine which course was more likely: acid-susceptible substances (like alkalies, or alkaline materials) would respond to the acid nature; oxidizable substances would respond to the oxidizing power (like organic alcohols and sugars).

An interesting case is pure iron: in dilute nitric acid (less than 10%), it dissolves. In concentrated nitric acid, it is oxidized (passivated) and does not dissolve. 

Increased temperature would also increase the likelihood of an oxidation reaction compared to an acidic reaction, because the activation energies for oxidations are usually higher.