I misspoke about the site you linked as admitting Dionysus death was associated with a tree, it was Attis. Yes, versions of the legend have his death caused by boar like Adonis was earlier. (worshipers of Adonis were like he jews forbidden to eat pork, Adonis was the name used by the Jews for their god at times (Adonai)). In other versions he castrated himself and bled to death under a pine tree, hence his worshipers depicted his effigy on a tree on a stick as an emblem of their cult.