Into the Void

Maple season proper is underway!  We’ve got some syrup under our belt now, and everything appears to be working as it should.  There’s still quite a bit of snow in the woods and the forecast looks reasonable.  We look forward to sharing this year’s crop with you: as we’ve mentioned, if you’d like to come up to Lyndhurst, you’re most welcome.  We might be a bit preoccupied, but the process is quite interesting if you’ve never seen it before.  Call ahead and wear rubber boots!

As I mentioned last week, the flow of sap is extremely weather dependent and often finicky: a few degrees or a north wind often spoiling conditions.  Being an important economic activity, sugarmakers have learned over the years to push things in their favour, the most significant factor being the adoption of vacuum technology to increase yields of sap.  In nearly all commercial operations today there’s at least one large vacuum pump at the heart of the system, steadily pulling every drop it can.

The Latin word vacuum means “empty, unoccupied, devoid of” and it is a bit of a trick to wrap our minds around.  It is counter intuitive because we don’t really witness a vacuum in nature, anywhere.  Anytime space is created, something fills it up.  Your diaphragm is trying to create a vacuum in your lungs right now, and they just end up filled with fresh air.  Even in outer space, the closest thing we have to a “perfect vacuum”, there are still a few Hydrogen molecules in every yard of the void.  The concept has been debated philosophically for thousands of years: can “nothing” truly exist?

Your household Hoover is the first thing that comes to mind when we think “vacuum”, but vacuum pumps are actually used in a myriad of applications.  Maple producers didn’t have to reinvent the wheel when it came to applying negative pressure.  Dairy farmers utilize it for milking of course.  Good old incandescent and fluorescent lights relied on vacuum (thus the interesting “pop” when they break). It’s also utilized in countless industrial applications: for example CNC machines often use vacuum as the “clamp” to hold the material they’re working on in place, and vacuum is employed in petroleum and chemical refining in ways that I will never grasp.  A great deal of vacuum tech maple producers use has been appropriated from the healthcare sector: hospitals have giant centralized systems plumbed throughout the building, and while you might not have thought about it while you were having your teeth poked and prodded with, that little tube in your mouth sucking up your saliva is hooked to a vacuum pump too.  You really can do just about anything with vacuum!

The measurement of negative pressure is one of those areas where the Metric rationalists haven’t fully sunk their boring claws, and here in North America for most practical applications we still measure vacuum in the magical unit of “Negative Inches of Mercury” which uses the nice round number of -29 Hg as its lowest point.  For every inch of mercury you put on a taphole, you will be rewarded with 5-8% more sap.  So, if you can put -20 Hg on your trees, you will easily produce over twice the syrup you would without it.   Of course, nature abhors a vacuum, so practically maintaining such a system is a logistical feat in itself, as various forms of entropy quickly undo the best laid plans of mice and men. 

And so, sugarmakers must patrol their bushes all season, making sure their tubing systems are taut and not leaking.  Trees and branches regularly fall on lines, fittings fail, and mischievous critters big and small like to gnaw on the plumbing.  Producers are now able to run incredibly strong vacuums upward (downward?) of -27 Hg, and not only apply manual labour to maintain this consistently, but will employ remote sensors in the bush to constantly monitor vacuum throughout the system.  How strong is -27 Hg?  Strong enough that researchers can measure the loss of moisture in the soil around a maple tree under high vacuum.

Should this be concerning for the health of the tree?  Canadians have been vacuuming trees for over thirty years at this point, and everything seems just fine.  First off, most of the harm that comes to a maple tree is actually done though the tapping wound itself.  High vacuum means that producers can use narrower taps, and get more sap from a single hole in a large tree, as one would hanging buckets all around it.  Consider also that it’s very normal for trees to lose sap: go for a stroll in the bush on this nice sunny afternoon and if you look closely, you’ll see sap leaking out of snapped limbs and splits in the maples: broken branches are a part of life for trees.  Not only are maples adapted to lose sap through their wounds, we’re learning that they actually strategically release it back into the soil through their roots: the sugary lifeblood stimulates soil biology, generating more soluble nutrients for the tree to feed on.

This symbiotic relationship also characterizes how humans and maples interact.  By rewarding us with sweet sweet syrup, we reciprocate the favour: selectively thinning the forest of the maples’ competitors, opening up more space for the crowns of the individual trees to grow.   After all, it’s the photosynthesis in the leaves that makes the sugar we harvest: bigger, healthier maples mean more syrup.  It’s win win.  There are so many relationships in nature like this: where it’s really hard to see who’s benefiting more.  I would also like to hope that this sort of co-operation characterizes how we work together with you too.  A back and forth that gets bigger, healthier – and sweeter – every year. 

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