Gordon Haverland wrote:Not many replies yet. Too bad.
You are talking about Wyoming? Jackalope country?
I'm just a little north of you, also on the eastern "half" of the Rockies. And due to global warming, we are approximately Zone 3b as well (some evidence to suggest possibly even into 4). And then we get a couple of winters with some cold days. Hard to say.
I've got a deer problem that involves itself in the windbreak. Also, my 40 acres is 1/2 mile by 1/8 mile, and it is the 1/8 mile that is perpendicular to some of our prevailing winds (we have winds a bit N of W or from the SW (nominally chinook/foehn wind)).
Most of the windbreaks I've studied are on the Great Plains or The Prairies. I suspect design heights are 40-60 feet tall (for 6 row windbreaks). How most farmers implemented them on The Prairies or in The Peace typically means they are only 20-30 feet tall. I like the conservative 7:1 ratio, so a 30 foot windbreak only shields to 210 feet downwind.
Much of the windbreak on the Great Plains or The Prairies assumes the land is nominally horizontal. Where I am, there are lots of hills (I'm on a north facing slope about 5 miles downwind of a 130 MW wind farm).
Since my land is only 660 feet wide, and in places all the trees on upwind neighbours property was cut more than 40 years ago (and my field was cleared entirely), I decided to look at the possibility of making the windbreak tall enough that it could shield the rest of my land.
Most of the forest here is trembling aspen and balsam poplar. To have 100 yards or more of either species, seems to stand up to wind okay (a mile of trees would be better). But, all kinds of people want the view and cut trees, and when you get to 100 feet or less of trees; they don't work One of my upwind abutting neighbours, cut all their aspen down 30-40 years ago, and then they seem to be willing to let them grow back now. They get to about 20 feet, and that's it. No more. And lots of breakage in looking at the scraggly mess of aspen.
All rows of a windbreak work together. Downwind rows project protection upwind, which helps the upwind rows. Row 1 mostly has the job of getting the wind started on an upwards trajectory. And it needs to be fairly good from ground level to something like 6-12 feet (for standard windbreaks - mine probably needs 20 feet). I think Row 2 is where you make or break a windbreak. It is going to be the row that really fights the wind. Guessing at how wide my windbreak would be, allowed me to guess how much shielding I needed (at 7:1), and so I am guessing I need a 85 foot tall windbreak. I don't know if my idea will work, I will be dead before it gets big enough. But, to go looking at 80+ foot tall trees in windy places, there were a lot of oaks. So, Row 2 is a white oak (Bur oak). Huge tree (windbreaks don't seem to use huge trees, there are missing pieces (circular triangles) on the leading and trailing edges which cause problems. Not fast growing, so you need other trees in the interim. And I need other trees anyway because of chinooks.
Row 3 is not a row, because it also has to fill in the trailing circular triangle of this big oak. It needs to block wind all year long from ground to top. Which probably means you need to fence it at ground level to keep animals from browsing or breaking branches. But, I think nut pines fit this. Both Korean pine and Siberian pine are Zone 2 trees. As near as I can tell, they tend to keep all their branches.
I need to grow fence posts (black locust and Osage-orange I hope). Because of the deer, Row 1 is to be a hedgerow involving both honey locust and Osage-orange. Much of the nurse trees on the windward and leeward sides of the nut pines, are to be honey locust and black locust.
The oaks need nurse trees to protect them from the chinook. A preferred nurse tree for oak is larch. The native larch like to live in a bog, which is not the clay that is my soil. European larch may work. Generic nurse trees seem to include mountain ash and hazels. And then I will fill in the field (at a 4 foot spacing) with the two locusts and Osage-orange. Part of the idea is to let these fast growing legume (and Osage-orange) trees start blocking wind. How tall you let any of them get, depends on the oak tree that is nearby. Eventually the oak should shade all of them out. I should be able to grow ordinary fence posts and probably corner/gate posts from this field. I would like to be able to grow honey locust sufficiently tall that I can get two rough 2x6 that are 16 feet long out of them. This might mean pollarding. If I try to grow 12 foot corner posts, they might need pollarding.
The oaks also have leading circular triangles. And something needs to grow in them. that gets significantly taller than 20 feet. Black locust could work. European larch might be nice. Basswood is another idea. Two of those, attract lots of bees (I don't think the larch attracts many bees).
The leeward half, is intended to be more random, so that we avoid "channels" that the wind flows through easily. The idea was the two locusts, because they produce little shading, so I could grow pasture under them. The other tree to put in there, was black walnut. It has been used in windbreaks. Makes more shade than the locusts. Black walnut is a valuable tree as wood. Black walnut may not form ripe nuts, but there are things one can do with green "black walnut". Butternut and Buartnut are walnut relatives/hybrids which probably grow faster than black walnut, and could work. In terms of juglone suppressing growth, back walnut is the worst of the family.
In terms of growing a mess of black locust at 4 foot spacing, Cornell seems to have a project farm which is doing this. And they are feeding animals (goats I believe) with some of the black locust leaves.
Maybe this generates some ideas for you?