They want to harvest everything now, all over the country, even the cut off tops left from logging, because pulp is such a hot commodity, because of the surge in flex fuel vehicles (E85). There are groups that want the lease rights to harvest the undergrowth and brush from the forests also. They are making machines right now that are like combines that go through the forest and munch up anything 12 feet or less in height.

Hemlock is low because of the fall of the housing industry.Deciduousis generally used for pulp, not coniferous. Too much pitch in coniferous. Coniferous is good for building houses mostly.
Hemlock is mostly used for floor joists, rafters, stringers and such.
You got your spf and then your hf grades for dimensional lumber. Depends on what you need for the part of the job you are working on. Some species lend well to certain areas of a building.
Another thing making hemlock less valued is the surge in engineered joists and rafters. No wonder hem is worthless right now.