Effect of Strengthening US Dollar on Commodities
Most global commodities are quoted (priced) in US dollars. The more valuable a dollar becomes relative to other currencies, all other things equal, the more commodity prices have to fall to equilibrate. Imagine everything was priced in corn and people start to value corn more or the amount of corn falls. Either way, all the prices in terms of corn (e.g. ears per barrel of oil) would have to fall as a result.