Tree of the Month for November, 2008: Abies balsamea, Part II
Part II: Range
As has already been mentioned, Abies balsamea is a tree of North America's Boreal forests. It likes its winters cold and long, and its summers short and mild. As might be expected of such a tree, it is very sensitive to an excess of heat, and if the temperature exceeds 65º F for too long, the tree may become damaged. Which implies, of course, that although the tree is abundant here in Maine, the climate here is really too hot for the tree! Yes, that's right, the Balsam Fir complains about Maine being too bloody warm! Which really does make sense, as the state is at the southern edge of the Boreal zone, and strictly speaking is better considered to be a transition area, climactically. And so, as can be seen, Maine really is near the southern edge of the tree's range. Again, as previously mentioned, it can be found growing in New York's Adirondacks, and there are scattered groves of it among the highest peaks of the Appalachians all the way down to Virginia, where it is gradually replaced by the closely related fraser fir. Sadly, that species is under serious threat, thanks to both an introduced insect pest, and its intolerance to air pollution & acid rain.
More interesting to me, though, is the species' northern and western limits in Canada. Compare them to those of one of its most common associates in the north woods, Picea glauca, the white spruce. You'll notice that the white spruce grows clear across Canada, climbing over the Canadian Rockies, and is stopped only by the mild air from the Pacific that grants even coastal Alaska such a temperate clime. This sort of distribution is common in other Nearctic Boreal tree species, such as the tamarack and the balsam poplar. You'll also notice that, when compared with these other species, the balsam fir doesn't grow nearly so far north. The others grow north beyond the Arctic Circle itself, to within miles of the frozen Arctic Ocean, allowing them to dispute amongst themselves and a handful of Eurasian species for the title of "World's Northernmost Tree"*. But the balsam fir isn't even in the running. It conks out well south of the Arctic Circle, and just west of the highest peaks of the Canadian Rockies. What gives? Well, the northern limit, at the least, is explained by the relative cold-hardiness of these several species. According to the ever-helpful Federal Silvics Manual, the January temperatures along the northern edge of the white spruce's range average out to 20 degrees below zero. Along the northern edge of A. balsamea's range, though, the January temperature merely averages at 0º F. Now, for a native Chicagoan like me, pretty much everything below 10º F is registered uniformly as "unbelievably friggin' cold", but these northern trees are true connoisseurs of cold and fanatics of frost, and to them there is a world of difference between the two temperatures. So it is that A. balsamea is stopped by the extreme cold of the Arctic and sub-Arctic north, and by the similarly extreme cold experienced along the inhospitable peaks of the Canadian Rockies.
But while this physiological explanation is certainly true, to me it really is not quite sufficient. I wonder, you see, why the balsam fir has not evolved the same cold-hardiness as its companions in the north woods. I mean, it's not like the fir is a more southerly species than its fellows - its southerly limits are roughly the same as the other boreal species of North America - so why should the evolutionary pressures which operated on them to grant them their extreme cold hardiness have failed to operate on the fir? I'm afraid that I have no answer to this question.
Not answering your questions since 1986,
--mark
*After doing some brief research on the 'net, it appears that the Winner of this particular title is the dahurian larch, Larix gmelinii, a native of Siberia, Mongolia, and Manchuria. The tree in question grows at the unbelievably high latitude of 72º 30' N, on the Tamyr Peninsula of Russia, the northernmost portion of the Eurasian landmass. Damn!
As has already been mentioned, Abies balsamea is a tree of North America's Boreal forests. It likes its winters cold and long, and its summers short and mild. As might be expected of such a tree, it is very sensitive to an excess of heat, and if the temperature exceeds 65º F for too long, the tree may become damaged. Which implies, of course, that although the tree is abundant here in Maine, the climate here is really too hot for the tree! Yes, that's right, the Balsam Fir complains about Maine being too bloody warm! Which really does make sense, as the state is at the southern edge of the Boreal zone, and strictly speaking is better considered to be a transition area, climactically. And so, as can be seen, Maine really is near the southern edge of the tree's range. Again, as previously mentioned, it can be found growing in New York's Adirondacks, and there are scattered groves of it among the highest peaks of the Appalachians all the way down to Virginia, where it is gradually replaced by the closely related fraser fir. Sadly, that species is under serious threat, thanks to both an introduced insect pest, and its intolerance to air pollution & acid rain.
More interesting to me, though, is the species' northern and western limits in Canada. Compare them to those of one of its most common associates in the north woods, Picea glauca, the white spruce. You'll notice that the white spruce grows clear across Canada, climbing over the Canadian Rockies, and is stopped only by the mild air from the Pacific that grants even coastal Alaska such a temperate clime. This sort of distribution is common in other Nearctic Boreal tree species, such as the tamarack and the balsam poplar. You'll also notice that, when compared with these other species, the balsam fir doesn't grow nearly so far north. The others grow north beyond the Arctic Circle itself, to within miles of the frozen Arctic Ocean, allowing them to dispute amongst themselves and a handful of Eurasian species for the title of "World's Northernmost Tree"*. But the balsam fir isn't even in the running. It conks out well south of the Arctic Circle, and just west of the highest peaks of the Canadian Rockies. What gives? Well, the northern limit, at the least, is explained by the relative cold-hardiness of these several species. According to the ever-helpful Federal Silvics Manual, the January temperatures along the northern edge of the white spruce's range average out to 20 degrees below zero. Along the northern edge of A. balsamea's range, though, the January temperature merely averages at 0º F. Now, for a native Chicagoan like me, pretty much everything below 10º F is registered uniformly as "unbelievably friggin' cold", but these northern trees are true connoisseurs of cold and fanatics of frost, and to them there is a world of difference between the two temperatures. So it is that A. balsamea is stopped by the extreme cold of the Arctic and sub-Arctic north, and by the similarly extreme cold experienced along the inhospitable peaks of the Canadian Rockies.
But while this physiological explanation is certainly true, to me it really is not quite sufficient. I wonder, you see, why the balsam fir has not evolved the same cold-hardiness as its companions in the north woods. I mean, it's not like the fir is a more southerly species than its fellows - its southerly limits are roughly the same as the other boreal species of North America - so why should the evolutionary pressures which operated on them to grant them their extreme cold hardiness have failed to operate on the fir? I'm afraid that I have no answer to this question.
Not answering your questions since 1986,
--mark
*After doing some brief research on the 'net, it appears that the Winner of this particular title is the dahurian larch, Larix gmelinii, a native of Siberia, Mongolia, and Manchuria. The tree in question grows at the unbelievably high latitude of 72º 30' N, on the Tamyr Peninsula of Russia, the northernmost portion of the Eurasian landmass. Damn!
