Tom and NTS folks:
Jim Kokenderfer, at the Parsons branch of the NE Forest Experiment Station, did a study, maybe about 20 years ago, showing that Norway spruce that had been overtopped by brush, could be released by an early fall application of glyphosate (roundup). Of course this won't work with annual weeds that can choke newly planted spruce. But, if anyone has a planting that has become overtopped by woody shrubs/saplings, there is this solution. What this research forester found is that the spruce develop a resistance to Glyphosate when the new growth has hardened somewhat, and it does this while the broadleaved woody plants are still vulnerable. I would guess that a search of Jim Kokenderfer, US forest Service, will turn up a link to this study, including the application amounts.
Another important thing to remember when "managing" pine and spruce plantations is this: I mentioned Professor Edwin White, former Dean of Research at the college of Environmental Science and Forestry at SUNY Syracuse, several times in posts for NTS, emphasizing how helpful he has been to me. One time when I was considering getting into a "forest stewardship" program to replace the "forest management agreement" program I was in, I was questioning the added flexibility I could have under this program. My project forester's said that I should thin my pines and spruces down to 100 square feet of basal area. For the uninitiated, the measure of basal area is a simple guideline that is used to determine the "density" of a forest, or how crowded the trees have become, and foresters often have guidelines for thinning a stand based on this measure.
Well, here is what Professor White told me. I had been keeping my pine and spruce plantations at a density of about 180 feet (I have my own prism, and doing the measurement is very easy), and that put me in conflict with the guidelines used by the MD forest service for certifying TSI thinnings, which was 100 feet. He said that for good growth of white pine and spruce, densities well over 200 feet were appropriate. And then he said, that if a "stewardship" program was designed to encourage long term preservation and growth of forests, that one could meet that criteria simply by refraining from destroying the forest. This last sentence is my summary of what he said in my own words. In essence, he said that after a plantation of spruce and pine have 'taken over" a site, that if the goal is to have a beautiful, magnificent mature forest in 100 to 150 years or so, one would not need to do anything at all. No thinning, no pruning, etc. That over that long a span of time, the individual trees would sort themselves out, with some asserting dominance, and nature would cause the overtopped trees to die, etc., leaving a mature, or old growth forest that would be very much like one that had been carefully managed.
Of course, that is not to say that some removal of defective trees that gain dominance won't add some fine trees to the final stand. And, of course a carefully managed forest will look much, much nicer in the meantime.
But, if any of you want to create something for "posterity," you need only take care of the seedlings after planting so they are not smothered by weeds, which will happen on the richer, "heavier" soils, and make sure they become dominant over whatever else manages to come up among them. "Nature" will then take over, and over the long term, a beautiful old growth stand will develop without any help from us.
But, and this is important--on some sites, some species of pine and spruce can stagnate, meaning that individual trees will not assert dominance, and the trees will become more and more crowded, and weaken, grow very slowly, and be susceptible to disease and insect attack. I have seen the stagnation of red pine plantations in Garrett County MD. But white pine and Norway spruce will always reliably assert dominance, and, ultimately, over the very long term, don't need to be thinned "artificially."
Now one of my excuses for the climbing I did to cut out the double leaders, even if thinking about the long, long term, is that in some places my plantations were understocked, so I needed to preserve all the trees I could. But, of course, the most important reason is my love of the trees, and just pure fun!