Where I live in coastal British Columbia and in many parts of the Pacific Northwest Douglas firs are the dominant tree species within 50 years of a fire or clear-cut. They are part of the natural succession and are by far the most valuable forest resource on the coast. Douglas firs put on wood quickly and that wood is stronger and denser than that of pines or true firs. These trees have less taper than many of the pines and therefore produce a greater percentage of useful sawn lumber. Large areas of northern Europe and New Zealand have been planted in firs because they are so superior to the native trees regarding speed of growth and quality of lumber.
As for the natives not valuing Douglas fir that has to do with the technology of the past. Long houses and other structures were built of cedar because it splits easily and is resistant to rot. When modern machinery is used these trees can be milled like any other. Today British Columbia's natives build with fir just as the rest of us do. Many reserves replant after forest fires or after logging with Douglas fir. And there are millions of acres of land claims working their way through the courts. These claims not only address native hunting and fishing rights but also forestry claims. For many who are not directly adjacent to the ocean their land which is perfect for growing Douglas fir is by far their greatest asset.
It's true that there is less biodiversity under a stand of evergreens. This is normal. During the first few years after a fire there are all manner of young trees, grasses and herbs but over time the trees shade out the others and herbivores which rely on early succession growth move on to new areas. The climax forest in this area is not Douglas fir since young firs can't germinate in dense shade. Hemlock are able to grow in very dark places and therefore the oldest forests on the coast are dominated by Hemlock. Hemlock forests produce very little for furry creatures to eat and this is the least bio diverse environment I have seen on the coast. But I don't think we should chop down our older forests to create greater diversity. We have millions of acres of clear-cut and areas affected by forest fire and pine beetles. During the first 50 years after these catastrophic events the new forest is very diverse.
Here in the mountains above Denver, conifers are about all there is. And yes, the under story can be pretty bare. There are Aspens which take over burns, only to be overtaken by the evergreens. There are cottonwoods and willows, but only along the creeks, and they are failing now that dams have (more or less) controlled the floods. (Not entirely; Boulder county was devastated by floods a few years ago. ) There are bushy scrub oak, and there are "invasive" Russian olive and Siberian Elm, also often along creeks, and not often in the high country.
So I suppose that the goal of a landowner who does not have climax forest here is to use fire and felling to keep the forest in the first 50 year stage that Dale mentioned, and maybe mix in some nonnative broadleaf trees.
NO!!! They are a mid-succession plant in an extremely long-cycle ecosystem. You can walk through a forest and tell that wherever a doug fir grows, it was once quite sunny in that spot. Prior to that, you know there was some disturbance. Western hemlocks are the inverse, showing that during their lifetime fire has not been present. Doug firs then live for up 800-1200yrs, and when they fall the ecosystem is more suitable for young tolerant loving trees like hemlocks, cedars, spruce or redwoods. Doug firs have the most diverse fungal associations of any western tree (350+, 80 endemic), and western hemlocks almost require their presence to inoculate the soil and provide moisture retaining nurse logs in in areas that have been disturbed and stripped of organic matter by fire or logging.
Also, the douglas fir "desert" would be the only one in the world that harbors perennial streams that naturally fill with salmon and trout runs.
This is all just my opinion based on a flawed memory
Here is a good article on Doug Fir ecology that is well worth reading http://and.lternet.edu/lter/pubs/pdf/pub34.pdf especially worth noting is how it discusses a diverse and well rounded ecosystem in old growth Doug Fir forests. In fact this diversity is being put forward as needed to be clasified as a legit old growth Doug Fir forest.
I think the issues of diversity deserts in Doug Fir and other conifer forests have a lot to do with human intervention rather than the true nature of these trees.
#1 issue likely is wild fire suppression. A lot of these forests evolved with regular fires running through them. We humans have really messed up much of the conifer forests due to trying to prevent and stop wild fires from doing what many of these forests actually need to happen.
#2 the devastation of massive logging in the past. A lot of the conifer forests were completely stripped. This utterly changed how the forests regrew. Fire does not strip entire mountain ranges of all it's forests typically. But we humans did exactly that, removing entire forests from all hills and mountains in our greed to take the lumber. The regrowth since then has been nature trying to bounce back from a massive disaster. This alone could be a big part of what knocked out a big part of the diversity that is cited as a problem with conifers. The under story would have been wiped out as collateral damage by the initial logging. While those loggers might have thought to replant some conifers, did they think to also plant in the understory plants? Modern logging you don't see understory planting along side of the tree replanting, so it is doubtful the old loggers thought to replant the understory either.
#3 human replanting. When humans replant they tend not to replant diversely. They also tend not to replant with succession in mind. They just plant the trees they want to log in the future.
The whole "natives burned out Doug Firs to favor oaks" seems like our culture killing off dandelions to preserve lawns. The natives valued a specific plant and so inhibited other plants from replacing them. But is this Doug Firs being invasive or natives artificially selecting what should grow in an area? To me this sounds like human intervention in succession rather than a problem with an invasive.
"Where will you drive your own picket stake? Where will you choose to make your stand? Give me a threshold, a specific point at which you will finally stop running, at which you will finally fight back." (Derrick Jensen)
Location: Redwood Country, Zone 9-10, 60" rain/yr,