WOW!snip<I was thinking in my climate it may dry to quick in pure pumice but I guess in a deep nursery can it wouldn't really matter so that's the way I probably would go thanks for the opinion. Also wouldn't it just be easier in the long run to remove burlap carfully and then pot up?>snip
Point of not removing the burlap is to not disturb the roots in the wrong season. There is no such thing as a "gentle repotting". Though I too would be tempted. Leaving it in the burlap is just an option, not required. When those more experienced than I say don't disturb the roots, they really mean just that. Every time you move the ball & burlap plant, the burlap flexes and shifts, the soil moves, many new root tips get broken off, this can lead to death of the tree if it happens too often. Soft flexible pots made of plastic or fabric have the same problem. Bouncing around a balled & burlap tree too often or too much can seriously stress or perhaps kill the tree. If it is not a good time to repot, I would personally leave the burlap in place. Each time the tree was moved this year new fine roots may have been broken, regrowing roots is stressful for a tree. You really want the tree to have a full set of roots before you do anything else to it like repotting, pruning, wiring, or anything else. The tree needs to get roots and start growing before anything else. I also would not prune any branches this winter, well maybe take off branches already broken, but certainly don't remove more than about a small fraction of the branches.
In my climate (between Chicago & Milwaukee, 2 miles from Lake Michigan) besides spring, we have an excellent second season for repotting, beginning middle August when it starts dropping below 65 F at night. It runs until about Sept 15th or so. Since average first frost is around October 29, the deadline of September 15 give you roughly 6 weeks of frost free weather to produce roots and have them harden off a bit. If you protect your trees in winter (keep them at or above freezing) you can repot even later into the autumn.
I don't know New Mexico weather, but if your climate allows repotting now, then by all means, do the repotting. But if it is not advised, the option I outlined will allow you to put off repotting. It's is just an option. Not something that you must do. Just threw it out as one way to handle it. I would caution you that the tree as it is at the nursery has already had the stress of being collected, then transported to the wholesaler, then the stress of being shipped to the nursery. Each time the tree was picked up and moved, the burlap flexed or shifted & some fine new roots were broken. As it sits at the nursery the pine has only a small percentage of its usual complement of fine feeder roots. I would treat this tree as a stressed tree. (of course, I can't see it, I could be wrong) If you could find out how long it was allowed to re-establish after collection, it might give you an idea whether the tree is likely stressed or not. If you can't find out, it would be safer to assume not enough recovery time was allowed. It's a guess, but a safer guess than assuming the tree is "ready to be worked on".
I have killed many pines over the years, and I try to figure out what I did wrong with each. Some I have had as long as 18 years, then got over enthusiastic, over pruned a tree that was repotted the same year, the tree was weaker than I thought and killed it. Others I killed their first year. Number one cause of my personal failures, is I tried to do too much, too soon without giving the trees enough time to recover. Read Vance Wood's posts about growing Mugo pine, and really take to heart that when it comes to Mugo's after a major activity, like repotting, letting the tree recover for a year or two really means - don't do anything else to it for 12 to 24 months or more. Vance's warning can to a large degree be generalized to most mountain pines. Repotting in the fall, and pruning late winter or spring is not giving the tree time to recover. Personally, I have had much better success with pines in general when I limit myself to only doing one major activity a year with them. Repotting I have had better success if I allow 2 years to pass before heavy pruning, major wiring, or extensive bud and needle work. Pruning and repotting less than 12 months apart often have proved fatal. (once in a while a tree survives and thrives, but my favorites that got the treatment died). Now pinion is not mugo, but if I had to guess, I would say you might have better success by treating the pinion more like a mugo than like a JBP. I could be wrong. But you won't hurt it by going slow.
I have zero experience with growing pinion pine, if one like yours were to me be dropped at my place today, I would go slow with it. I would just set it in a pot, burlap intact, wait until an ideal repotting time. Then when I repot, I would give it 12 to 24 months to settle in and give myself time to get familiar with how it grows. But that is me, with my pile of expensive firewood behind me. If your horticulture skills are good, you can get away with a lot more than I can. I know my hort skills are not top notch. So I advise caution.
Sorry if it sounds like I'm coming off strong, or strident. Not my intent, but I want to pass on my experience and clearly identify why I suggest what I do. Hope this helps.
Again, nice tree, nice find and hope it is with you 2 decades from now.
Great book!