Continuing with the theme of the left-behind… I do a lot of peering at branches in the winter months, after most life has gone into hiding. Sometimes some interesting discoveries can be made, affixed to (or even within) twigs or branches. I took Raven down to the 100-acre Woods yesterday, the first time we’ve gone in a little while because of hunting season (we’re in the mid-November hunting lull at the moment, but we wore our brightly-coloured jackets, just to be safe; I don’t think anyone hunts on that bit of land, but who knows what goes on there when no one’s around to see it). The forest has a fair bit of Balsam Fir scattered through the damper areas, and I paused at one clump to finger the needles, whereupon I noticed these odd little lumps amidst the foliage. There were a lot of them, mostly at the outer ends of the branches, and mostly (it seemed) on the east side of the tree (though that might just be coincidence).
Determining their identity was fairly easy once home. A Google image search for “balsam fir needle galls” turned up several pages with identical galls to mine. Gotta love the forestry industry’s thoroughness; virtually anything you want to know about pests of commercially valuable tree species is available online. The pest in question here is a tiny midge, Paradiplosis tumifex, which goes by the appropriate English name Balsam Gall Midge.
Eggs are laid on current-year needles as they’re growing (which explains why the galls seemed mostly to be near the ends of branches), and when the egg hatches the larvae burrow into the needle to settle down and feed. The needle forms a gall around the larva and its new home. The larva eats and grows and eats and grows, until mid-autumn when they finally break loose of their gall and drop to the ground. There, they burrow into the soil under the tree and wait for spring. Warming ground temperatures in late April and early May encourage the larvae to pupate, and a week or two later the tiny adults begin to emerge. Females mate, then return to the newly-forming fir needles where they lay their eggs, and the cycle begins again.
Once the larvae leave the needles in the fall, the needles brown and drop from the tree. The branches were scattered with the ones that had caught in the twigs. I noticed on the ones that were still attached to the branch that a few of them seem to be broken off; I’m not sure if this was from the midge larva emerging, or environmental damage post-emergence. The midges are no more than a nuisance, apparently; they do no long-term damage to the tree, beyond perhaps mildly stunted growth that year when under severe outbreak conditions. The galls are dropped by the winter, and even aesthetically the tree looks fine again quickly (important for the Christmas Tree market). Populations are cyclical, with two or three years of high numbers, followed by several of low. I can’t remember having noticed anything unusual about this same tree last year (it grows beside the path), and I’m not sure if that’s because numbers were low last year and high this year, or I just wasn’t looking.
One of my primary reasons for starting up this blog, nearly three years ago, was that it would encourage me to learn new things about the world around me. And so it has. Most of the time it’s through my discovery of something interesting or unusual that I come across while out hiking (or sometimes it comes to me), and which I then look up more info on once I get home.
Recently, I was approached about whether I might be interested in slightly revising my book review of Tracks & Sign of Insects, which I’d posted here on the blog back in May, for inclusion in a Vermont-based magazine called Northern Woodlands. The magazine is an interesting mix of articles, somewhere at the meeting place of forest “management”, forest exploitation, and forest appreciation. I admit to being a bit of a purist – the thought that some people feel the need to “manage” their forests in order to make their forests “healthier” really bothers me, and while I recognize the need for lumber and tree harvesting (and even don’t mind most forestry practices, to some degree), it still hurts my heart a bit to see a forest put to that use.
So when I got my copy of the magazine in the mail, I skimmed over all those articles. There are still quite a number that fall into the “appreciation” category, however, and more than once I found myself thinking, I didn’t know that, that’s so neat!
One such article was relatively fresh in my mind while I was out walking our own woods a couple of days ago. We don’t have very much woods, or at least not walkable woods, here on our 30-acre parcel (most of it is down the road at the 100-acre bit). Much of what occurs here is wet, especially at this time of year. There’s a small patch near the back which I sometimes cut back through and then wander along the strip of forest at the edge of the property (actually just the edge of a larger expanse of woods, but the fence of the property line runs through it and only a little bit bleeds over from the neighbour’s land onto our own).
I was watching my step as I came around through the trees, making sure I didn’t trip over anything, when I spotted these leaves. A month ago, before I’d received the magazine, not only would not have known what was going on here but I probably wouldn’t have even noticed them in the first place, mixed in with the rest of the fallen leaves (see top photo). But there’d been a short half-page article on them in the magazine, and so stopped and gathered a bunch together so I could take a photo to share with you guys here on the blog.
You’ll have noticed that they’re all poplar leaves, and that all of the leaves seem to have one section of the leaf, in most cases between the first and second major diagonal veins, which has remained green. A closer inspection reveals a small blemish at the base of this green strip, butted up against the mid-rib and the lower vein. If you examine this under magnification (some folks carry pocket loupes in the field with them, but if you lack one you can flip your binoculars upside down and look through the wrong end, holding the object a centimeter / half inch away from the lens, to the same effect) you’ll see a little worm tucked in the blemish.
The worm is a caterpillar of a moth in the genus Ectoedemia. It’s just a little moth, less than a centimeter/half inch long, with long, narrow, blue-gray wings and a fluffy orange head. The caterpillars are late feeders – perhaps a strategy to avoid the predation pressure of breeding birds searching for food for their young? – feeding on the leaves well into the fall. So late, in fact, that the leaves drop from the trees while the caterpillars are still munching on them. It does the caterpillar no good to be chewing on a dead leaf, so it ends up secreting a type of plant hormone that keeps the leaf alive for a while longer. The article doesn’t specify, but I suspect that, given this strategy, the caterpillars cocoon within the fallen leaves and then pupate and emerge as adults in the spring.
The first flowering tree to produce blossoms in spring here, right after the yellow Forsythia bushes, and before the apple trees, seems to be the serviceberry. There are several different species of serviceberry in Ontario, and I’m not certain which one this is, but the Allegheny Serviceberry (Amelanchier laevis) is among the more common in our area. We have a couple of serviceberry trees not far from the house, set back in the first field. The larger of the two stands guard over the nestbox the bluebirds nested in last summer, almost but not quite nestled in its branches. I hadn’t paid too much attention to the tree last summer – being past its spring blooming it was unremarkable, bearing generic oval leaves and having a rather plain trunk – so its spring display took me by surprise. Its flowers remind me of thin, loose cherry or apple blossoms – perhaps not too surprising, since it’s in the same family, Rosaceae. My mom recently did a nice post about serviceberries with some further information about them – check it out here.
I was away this weekend, down to Toronto for a writers’ conference which was a lot of fun and also very informative. I opted to leave my computer at home as a break from the obsessive email-checking, so I missed getting any posts up while I was gone. I should be returning to my usual frequency now that I’m home again.
We’ve been having some warmer temperatures over the last couple of weeks. Warmer being a relative term, of course – most days it’s still at or below freezing, though perhaps not by much. We’ve had sprinklings of snow on a few days, though it hasn’t accumulated to much. Most days, however, have been sunny. Today is yet another sunny day. I’ve been noticing some snow melt as a result of all the sun, which can warm surfaces up above the freezing point. On our driveway and areas that receive a lot of traffic you can actually see the bare ground now. Also around the edges of the buildings where the snow doesn’t pile up as much because of drift patterns and the overhanging eaves. There’s bare ground under the evergreen trees, whose spreading boughs prevent deep accumulation of snow. And of course, there are the melt rings at the bases of tree trunks.
When I snapped these photos out in the 100-acre woods I thought this would be a pretty quick and easy post. Short, not much to say, right? There had to be dozens of posts talking about this exceptionally common phenomenon, right? Surprisingly, no. When I googled it today, most of the pages asking about it were things like Yahoo Answers, WikiAnswers, Answerbag, and similar. And judging from the great number and variety of answers posted to these questions, no one really seems to know.
The answer that seems to be mentioned the most is that the dark tree trunks absorb the warmth from the sun (even on cloudy days, some light still makes it through) and re-radiate it back into the environment; even just the slight rise in temperature from this is enough to melt the snow. Other explanations put forth were that the area under trees receives less snow to begin with; that the snow in the boughs of the trees melts and causes water to run or drip down the tree, melting the snow at the base; less grass means more geothermal heat rises from the ground under a tree than in the open; and turbulence caused by the wind breaking around the tree carries moisture away faster than in open areas.
I don’t know if anyone has done a rigorous scientific study to really say definitively. However, I found this study, which measured snow depth and ground surface temperature (where the ground and the snow meet) to a radius of 6 meters (20 feet) from a tree trunk. Their results showed that early in the season, snow under the pine tree being measured was only a third of what it was in the open, and by late in the season it was just a fifth. Probably because there was less insulative snow cover under the tree, ground temperatures closer to the tree were colder than those farther from the tree (this also meant the ground was frozen to a deeper depth under the tree than away from it).
To me it’s the re-radiation of heat from the trunks that makes the most sense, especially since in many cases the sunnier south side of the tree showed more melt than the north side. I’m surprised not to find anything definitively explaining the phenomenon, though.
During the winter, each month, it seems, comes with its own affliction. I just got through the January Itch, and now I’m facing the February Slump. January is the time of the winter when I first start tiring of the cold and the snow and the relatively depauperate faunal landscape. It’s January when I typically do foolish things such as start up a nature blog or invent other projects for myself. By February, I’m nearly burnt out with winter. By February, I’m starting to struggle for blog fodder, but I’m also struggling for the enthusiasm to search for blog fodder. Mostly I’d prefer to curl up in front of the fire with a good book and wait for spring to arrive. The groundhog usually tells us there’s six more weeks of winter, which isn’t terribly surprising, because spring usually arrives sometime around mid-March up here. That’s when we can start expecting the first really prolonged thaws, though we might have a day or two, here and there, of mild temperatures prior to that.
That’s a long way of saying, please forgive me if my posts are a little sparser this month than they usually are. I promise they’ll start to pick up again when I catch March Madness with the mild weather next month. (Jason – please note overly wordy introduction that has nothing to do with main post subject.)
I dug through some of my archived photos looking for something I hadn’t posted yet. Fortunately, I always have a backlog of things. These photos were taken on January 15, but the great thing about trees is that I could go out tomorrow and get nearly exactly the same photos. So timing doesn’t tend to matter as much with trees, at least not in this season.
I walk past this patch of trees on most visits to the 100-acre woods. When I first discovered it, I thought it was Black Spruce. I’d seen Black Spruce in only a couple of locations before: in northern Ontario when I drove along Highway 11 on one of my trips west, it’s the predominant species along the highways there; and in the fen at Rock Ridge. It’s not a lot of experience to draw from, but hey, it’s what I’ve got. What I remembered about them was mostly that they were very narrow trees, almost spindly. Many, though not all, of them had round clumps at their top. But it was the narrow spindly that really stuck with me, they were the only evergreen I knew that grew narrow spindly. So I saw these, and they were very tall, narrow, sort of spindly spruce-like trees. So naturally I assumed they were Black Spruce.
Now, I’ll be the first to admit that I’m far from being a plant expert. I specifically majored in Zoology and not Botany in university so that I wouldn’t have to learn all that boring plant crap. Turned out a lot of what I learned was boring animal crap and it probably wouldn’t have mattered all that much. In retrospect, I’m pretty sure it was just the environment that made it boring. I find plants much more interesting now than I did then, but that’s probably because I’m learning it all on my terms. And I don’t have to regurgitate it on an exam.
So not being a plant expert, it escaped my notice for nigh on half a year that these were not, in fact, Black Spruce (you’d think the fact that they weren’t growing in wet habitat might’ve tipped me off but no, I just labeled it unusual). Finally, in January, it occurred to me to go over and take a closer look. And wouldn’t you know it: not spruce. So then the question becomes, well, what are they then?
Although there are clues in the needles, the most definitive feature was the trunk. Those narrow, colourful spots that seem to go around the trunk in circular bands are diagnostic of Balsam Fir. You can’t see it as much on the front tree, but on the rear trunk you can also see some of them are raised. These bumps are “resin blisters”, pockets of pitch that form just under the surface of the bark. It’s possible to pop these just with your finger, releasing the sticky substance inside. I’m not clear on why the tree creates pockets of the stuff, but the pitch is used basically the same way as in other species: defense against intruding insects or infections, and to speed closure of wounds.
Balsam Fir are found through the Boreal forest, from northern Alberta east to Newfoundland and Labrador, and south through southern Ontario into the northern states. Given that they’re not restricted to the Shield, I don’t know why I’d never encountered one “in the wild” before (they are, of course, popular Christmas trees, but they’re more expensive than the pines or spruce – perhaps they grow more slowly – and so we never got them, usually opting for spruce). My suspicion is that I was mistaking them for Eastern Hemlock, which look superficially similar. I guess I never really took a close look at the needles, or paid much attention to the trunks. If I’d looked at the trunks, I’d’ve realized that firs have smooth, spotted trunks, spruces have slightly scaly trunks, and hemlocks have ridged trunks. Seems pretty easy now that I know.
The needles of spruce come out of the twig from both top and bottom, while hemlock and fir are either flat, or (sometimes with fir, it appears) only on the top half of the twig. The difference between hemlock needles and fir needles is in their length (fir are longer) and their “stalks”, the narrow bit that attaches the needle to the twig. In firs (previous photo) this stalk is not much narrower than the leaf itself, while in hemlocks (above photo) there is a distinct, thin stalk at the base of the needle. (Sorry for the quality of this image, sure looked like it was in focus on the LCD screen). There seems to often be a slight different in colour, too, with firs a yellow-green and hemlocks a forest green or grass green, as you can see in this convenient side-by-side comparison, below, though this probably is affected by local conditions and individual variation, too.
Balsam Fir, it turns out, has a lot of uses. Christmas trees are one, of course, and the wood is often harvested and sold as lumber, either under its own label or sometimes lumped in with spruce.
The pitch apparently has antiseptic, anti-inflammatory and analgesic properties and was used by Native Americans as both topical salves for wounds or chapped lips, and as a tea infusion for internal ailments, particularly colds and flus but also other health problems like infections or arthritis. I gather that, should you cut yourself while out in the woods, you can apply Balsam Fir pitch directly to the wound and it will seal it and help it heal.
It can also make a great fire-starter; pitch smeared on damp wood will burn for an extended period, often long enough to dry out the wood enough to allow it to catch. I saw a mention of its use as a fly trap, smeared on the back of, say, a hard hat where it will catch deer flies when they come to land. Plus it would smell lovely at the same time. Wikipedia mentioned the oil could be used as a natural rodent repellent. It also said the pitch can be used in the preparation of permanent microscope slide mounts (that is, place a dab of pitch on the slide, over your specimen, and add another slide or a cover; the pitch will dry clear and hard and preserve the specimen). Wikipedia also implied (the wording is a bit fuzzy) that historically some binoculars used Balsam Fir pitch to glue the lenses in place.
Now that I’m finally aware of the presence of the species around here, I wonder where else I may have seen it and simply written it off as spruce or hemlock. Was there fir around the lake house? Our MAPS stations? The bark pattern looks familiar, but I can’t be certain, now. Something to watch for in the future.