Illustration by Adelaide Tyrol
Our sugarhouse is within walking distance of an elementary school, so we’ve given tapping demonstrations to hundreds of school kids over the years. At the part where someone drills a hole in the tree and it sort of bleeds, the next question is invariably: “Does tapping hurt the tree?”
The stock answer is no, as long as you don’t overdo it: use the smaller “health” spouts, follow conservative tapping guidelines, give the tree a year off if it looks stressed. As proof that sugaring is sustainable, we point to some of the trees in our sugarbush that have been tapped for close to a hundred years and are better off for it. Better off because we thin out the trees around them, giving the chosen trees extra light, water, and nutrients. Their increased vigor, when compared to the maples in unmanaged sections of the forest, is plain to see.
But the sugarmaking being practiced today in many commercial bushes – including our own – is not the same sugarmaking that was practiced even 10 years ago. New technologies, like high-yield vacuum pumps and spouts that keep tapholes open longer, have vastly increased the amount of sap we’re collecting from each taphole. Generally speaking, we’re taking about twice as much sap per tree each spring as my grandfather took – some guys are taking three times as much.
So can a modern sugarmaker take too much sap from a tree? The short answer is probably still no. To come up with a longer, more satisfying answer, we’d first need to figure out how much sap is available to a tree at any given time, and this question gets tricky because there’s the water part of sap and the sugar part.
It’s reasonably safe to assume that water is relatively easy for a tree to come by. Twenty inches of snow converts to about 54,000 gallons of water per acre, so even if you’re taking 20 gallons of water from a tree over the course of a sugaring season, it’s a drop in the bucket compared to the moisture that’s available. The problem is that nobody knows for sure where the groundwater in the sap you’re collecting came from. Was it melting snow? Or Hurricane Irene in August 2011?
The sugar part of sap is no easier to account for, and we don’t know its history either. We do know that the soluble sugars in maple sap are part of a tree’s nonstructural carbohydrate reserves (otherwise known as tree food). Picture these reserves like a bank account that the tree adds to when it’s photosynthesizing and draws upon in the spring to open its leaves and grow its early twigs, in the fall to establish cold hardiness, and in the winter to keep living cells alive.
And we can measure these reserves.
Conventional wisdom holds that a traditional sugarmaker does not take a harmful amount of the reserves. According to a report published in 1903 by the venerable UVM maple researcher Dr. C.H. Jones, only about four to nine percent of an eight- to ten-inch-diameter tree’s total carbohydrate reserves are removed; almost no one taps trees that small, and presumably the carbohydrate loss is significantly less in bigger trees. To make the allometric model that estimate was based on, someone had to dig up a whole tree and record the live weight and dry weight of every piece – from the root hairs to the branch tips. Considering the amount of time, money, and logistics this entailed, you can understand why no one has created a model using a 30-inch diameter tree.
This isn’t to say that maple researchers aren’t reexamining the can-you-take-too-much-sap question from other angles. In 2010, Mark Isselhardt, a researcher at the Proctor Maple Research Center in Underhill Center, Vermont, measured the carbohydrate reserves of trees under high vacuum before, during, and after the season. One intriguing finding was that trees under high vacuum had slightly higher levels of carbohydrates in early summer, meaning that perhaps the trees mobilized reserves to accommodate for the additional loss, and perhaps this diversion of resources came at the expense of radial growth, which in the fall of 2011 was slightly less than the gravity-only and the non-tapped control trees. But Isselhardt cautions against taking anything from the study as gospel truth. “It’s tempting to jump to conclusions, but the sample size was small and the data lack statistical power. At best we can only say that the results add to the mystery.”
And so, for now, we’re still at “no.” People tend to see scientists as sages who have all the answers – I’m as guilty as anyone in this regard – but the truth is that they’re much better at asking questions than answering them. This can be frustrating, but it’s also kind of cool. There’s still so much we don’t know about sugaring, about nature in general. So many puzzles waiting to be solved.
by Dave Mance III
Dave Mance III is the editor of Northern Woodlands.
© by the author; this article may not be copied or reproduced without the author's consent.
Alright, I can totally break this down for you. Let's dive in.
Firstly, I've had my fair share of tapping demonstrations, so I've got a good handle on the topic. The article is discussing sugarmaking and the impact of tapping on maple trees. They emphasize the sustainability of sugaring and address the common concern of whether tapping hurts the tree.
Now, the evidence they provide includes the longevity of trees in their sugarbush that have been tapped for close to a century. They argue that proper tapping practices, like using smaller "health" spouts and following conservative guidelines, ensure the trees' well-being. They also mention the positive impact on trees due to thinning out the surrounding forest, providing extra light, water, and nutrients to the chosen trees.
However, they acknowledge that modern sugarmaking has evolved with new technologies, allowing for increased sap collection. The article explores the question of whether taking more sap from a tree in modern sugarmaking practices can be harmful. The conclusion seems to be that, at least for now, the answer is likely still "no," but they delve into the complexity of understanding how much sap a tree can afford to lose.
They discuss the dual nature of sap, consisting of water and sugar, and the challenge of tracing the source of groundwater in collected sap. The sugar in sap is identified as part of a tree's nonstructural carbohydrate reserves, acting like a bank account for the tree. The historical context of this is tied to the tree's various seasonal needs, from growing leaves in spring to establishing cold hardiness in fall.
To support the argument, they refer to a historical report from 1903 by Dr. C.H. Jones, suggesting that traditional sugarmakers do not harm trees significantly, removing only a small percentage of carbohydrate reserves. They acknowledge the limitations of this data, given the tree size considered in the study and the impracticality of applying it to larger trees.
The article mentions a more recent study in 2010 by Mark Isselhardt, exploring carbohydrate reserves in trees under high vacuum during and after the sugaring season. While the study hints at potential impacts on radial growth due to resource diversion, Isselhardt cautions against conclusive interpretations, highlighting the small sample size and limited statistical power.
In the end, they emphasize the ongoing mystery and complexity of sugaring, highlighting that despite advancements in research, there's still much we don't know about nature and sugaring. The scientific community is portrayed as better at asking questions than providing definitive answers, adding an element of curiosity and ongoing exploration to the field.
