Howdy, I live in CA, but have carried my bows to NE on vacation and collected wood in NE. Relative humidity will be lower, especially during the winter, but I don't think you'll have any problems with the woods you mentioned. The plains of eastern Co are largely treeless, but trees can be found along the foot hills and along water out on the plains. Three woods that I know you can find in the Denver area and east are;
1) junipers--ERC and Rocky Mountain juniper will both work though a backing of sinew or rawhide would be insurance against breaking.
2) Russian olive can be found throughout the great plains. It's an invasive exotic, so feel free to cut all you want ( with the landowner's permission.) I have yet to obtain a stave of this, but by all reports, it works well.
3) Elms Siberian elm is another exotic, locals will call it 'chinese' elm. It was and is widely planted for windrows. It's not as strong as some other elms but can provide some nice straight staves if you're wiling to go to the work of splitting elm. Use plenty of wedges! American elm is also available, but more likely to be a street tree.
Other trees that you might be able to find; osage orange- not native but it was occasionally planted as hedges in Nebraska and possibly in eastern CO
Choke cherry- more likely to be found in the foothills
Ash- A tree that I've seen along the north platte river in western NE, but I'm not sure how wide spread it is in CO.
Mulberry- White and red mulberries are spread across the great plains.
Other's who are living in the area may be able to add to the list. I now that bcbull is not too far away. maybe he'll chime in. Ron
