My pug barks at a vase i have on the fireplace mantel, does anybody know why?

There are lots of reasons a dog might fixate on something like that. First make sure it is the vase, by moving it to a different location and seeing if you get the same reaction. Then try letting her investigate the vase by holding it where she can sniff it all over. If it still freaks her out, try giving her treats next to the vase until she builds a positive ociation with it. You could even store some treats in it so that every time you go over to the vase you pull out a yummy treat. That could make a dog very fond of a vase.