Working with a grad student in the Lost 40 yesterday, trying to get some lines set up for some research climbs this fall/winter/spring.

The Lost 40, about an hour N of Bemidji (about half way to the N pole, in case you Georgia guys were wondering), has the tallest white pines in Minnesota, so it's a good place to look at what might limit tree height growth. We know from earlier work that drought stress has a lot to do with it, but the next question is whether the winter is also a factor.

Anyway... We were trying to set up some routes on the bigger trees (around here that means a measly 120-140 feet), and by dint of a lot of throwline work got into a tree we were calling "Semi". Semi looked pretty good from the ground; a couple of broken branches at odd angles up there, but mostly sturdy looking stuff, with a full crown and well within the upper range of height. Three pitches later, and maybe 75-80 feet up, we got a good look at our "sturdy looking stuff" from the top.

Porcupine blazes - patches where a porcupine had chowed down on the inner bark of the branches (porcs only go after tree bark in the winter, but in the winter it's just about all they eat). On white pines blazes always occur on the upper surfaces of branches, and are usually ovals about 10 X 5 inches. Judging from the continued growth of the branches around them, these were from activity maybe 10-20 years ago. The exposed wood was breaking down some, and the narrowing of the branch profile created structural stress risers at the blazes. Here was the explanation for the oddly broken branches; they snapped in windstorms in mid-span at the weakened parts. Almost all of the nice large limbs had 2-5 blazes.

This was not really a problem for anything we were hanging on; our tips were stout and still living, and we were right against the trunk. The problem was with the usefulness of the tree for research. Our sampling plan entails running vertical transects through the canopy some distance away from the trunk. The more I thought about it, the less I liked
branch walking (with GOOD support from above) and redirects on limbs that looked like this.

Darn.

Oh well, an afternoon in a tree is never wasted time, and we do have some other prospects ("Nopathy" and "Eileen" are still nice and sound, and "Dagger" might be worth another look).

Has anyone else seen a pine this chewed on by porcupines?

I've seen pine chewed by porcupine but never a big one that I was climbing. Typical scenario is there are plenty of smaller pines in the general area of bigger ones so their choice of tree to dine on is fairly random. Whatever is less energy to climb I guess. Then again who knows what's in the mind of those inscrutable creatures, they remind me of giant hamsters with spines

By the way... 120' - 140' is no slouch of a white pine The way I look at it a wild white pine over 100-110' is officially in the "adventure" category of tree climbing.
-AJ

It apparently looks random to us, but one of the reasons porcs revisit the same trees is that some trees just taste better (in techno-speak: have different proportions of defensive secondary compounds). Partly this is explainable from measurable proportions of different nasty tasting stuff, partly it seems to be a matter of the individual preferences of the porc.

I see a blaze or two on almost any really big white pine I've ever climbed, but I've never seen one this seriously structurally compromised.

Aha! I was wondering about that, it is thought that yellow-bellied sapsucker (woodpecker species to the uninitiated) prefers the sap of one tree of the same species over another for the same reasons.

We don't have porcupine in far eastern Mass. but when I climb in western Mass. I see porcupine regularly but not much in the way of tree damage. Guessing you have higher porc population density in the ungodly far northern climes of Minnesota!
-AJ

Guys. Have you considered the third possibility. This seems to be happening to the tallest trees during the winter and well north of the Mason Dixon line. Who's to say that the porcupine didn't just waddle up across the snow drifts and dig DOWN through the snow to reach the nearest branch to feast on? Any tree less than 60 or 70 feet tall was too short to make it out of the protective snow cover and were well shielded from this winter predation. This is Minnesota we're talking about after all.
You know, great minds think alike, but so do simple ones. So, what does that tell ya?
Wiley Coyote

Brilliant!

Aww now... The snow doesn't get that deep up here - 50 feet tops, and less than 10 feet in the summer.