Setting: Just east of Snoqualmie Pass yesterday. We went out to trail animals, but didn't find any trails of particular interest to us. We did however see some interesting natural history. I noticed this tree had a bunch of twigs underneath it, mostly of similar lengths, and that other trees nearby did not. So I went over to investigate and this is what I found.
1. What species of tree? (A warning that if you are like me, the close up of the twigs might trick you.)
This was a grand fir (Abies grandis). I don't know if I would have been able to determine that from looking at these pictures (though I imagine that people more knowledgeable about these trees might have been able to). Usually the way I identify grand fir is by the single flat row of needles on each side of the branches. And that is what the lower branches on this tree looked like. I think though that higher (younger?) branches often look a bit different as these twigs do that were clipped and fell to the ground.
Knowing what tree these came from and working backwards, I notice that these twigs seem almost as though the standard needle pattern was smooshed upward together. When I compare it to twigs I found in similar situations under different tree species (other Abies and Pseudotsuga), they have a lot more needles than the grand fir does on any give horizontal slice of the twig.
2. What is the deal with the twigs?
These twigs were clipped and/or broken off by an animal and the buds were eaten. I suspect that the buds are mainly those of the male cones, but I'm really not sure. Maybe someone can answer that in the comments?
The fact that the twigs were clipped in such a manner strongly suggest mammals, and there aren't a lot of options for mammals comfortable in trees out on branches that small in this area. At first we considered tree vole, because we had recently had a conversation about how voles frequently cut vegetation to about that length. However it turns out there aren't tree voles in that area. I believe that pretty much limits us to the douglas squirrel (Tamiasciurus douglasii) who I imagine are enjoying the buds as a nice spring meal.
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8 comments:
Okay, I keep going back and forth between a Subalpine fir (Abies lasiocarpa) and a Doug Fir (Pseudotsuga menziesii). The presence or absence of pointy red buds would be diagnostic for a Doug Fir, but alas they aren't present. I was kind of stuck on a fir because of habitat and the rather round leaf scars, but I can't quite conjure hockey sticks out of the needle bases. Both trees would show 2 stomatal bands on the lower surface, but only the fir would show one on the upper surface. Didn't see any on the upper surface, so Doug Fir. The not so close up photo shows a tree that looks alot more like a Doug Fir. Okay, so I'll go with Doug Fir.
The much less over thought answer to the who/what question is Mountain beaver. Seems like I read that they cut twigs at a 45 degree angle.
A little more context: I think the location we were at was around 2400 feet in elevation.
I like your reasoning process, however I think there is a bud on the close up that you missed. I'm curious why you are limiting your considerations to those two species?
Good observation about the angle of the cuts, unfortunately a lot of mammals make such angles. Ungulates are an exception to that, so I usually use that characteristic to help me decide whether something was browsed by an ungulate, or a non-ungulate.
Something that might be worth considering: where on the tree are the buds like that?
thanks for the tips. I eliminated other genera, eg pines by the lack of needle bundles, spruce by the round needle tips and lack of pegs on the twigs, and hemlocks because the needle arrangement and length.
I probably should have considered Abies amabilis, there aren't stomata on the upper surface and the rounded bud (thanks for pointing it out) looks more like a fir. I thought that the needles of that species had a more pronounced notch at the tip. I did dig out an ancient field book with species lists from near there and noticed alot of A. amabilis in the releves. I eliminated A. grandis because of the needle arrangement (and site?)A. procera because I don't think it grows in northern WA.
Nice, very thorough. Still incorrect though :) (At least I hope so, I'm pretty sure I made the correct id in the field). Like I said, the close up is a bit confusing.
I think I have seen Abies procera up there, but I haven't seen a lot of it. I was looking through Pojar as a result of this exchange, and they use some confusing images for the fir foliage. Their A. procera picture looks a lot like A. amabilis to me. I guess it is good to know that they are so confusable at times, but would think it would be better to go with images of characteristic looking foliage.
Okay, I'm a bit stuck. I worked through the characters again. I eliminated A. lasiocarpa and procera because there aren't stomata on the upper surface. That leaves me back at Doug Fir, because I eliminated the rest of the genera, perhaps inappropriately. Perhaps I need to reconsider.
I guess so. Though if you wait much longer you will be able to get the answer the easy way.
The easy way is sounding pretty good at the moment, I've arrived at the point where I'm just curious about where I went wrong, but I'll probablly look at it again.
It is getting a bit more spring-like up here, I found Early Blueberry in bloom yesterday evening
That's exciting. I saw your blog post the other day about hearing the winter wren singing too.
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