Well, when I was reading CRB commodity year book about 8 month ago this is what they put in there...of course I am using my words.
As commodities are trading in USD, they are influenced by the price. If, the dollar declines....same as it happened throughout last 2+ years the price of commodity rises.
Take this for example, the commodity cost 6 pounds of gold for one barrel of oil. Assuming that the price and the price of gold ALWAYS stays the same. The price of the dollar depreciates. So, then the price of a commodity will go up.
THE point is, when dollar depreciates then the commodity price climbs up. Of course assuming that the commodity is priced in USD.