maple research

[DrTimPerkins]

Looking for input....

Keeping in mind that depending upon the question, the funding, the time we have available, and interest...

What types of questions do you have that you think we might be able to address via doing a research project?

No promises, and it can take years before we get through the process (in many cases we like to have 2-3 seasons of results before we talk about it), but just interested in hearing some ideas. The bigger the question, the harder and longer it can take...and not all questions are readily answerable. NO promises that we'll actually do these, but something might work out. Note that if you ask something that has already been done I may just point you to the resource with the answer.

[Biz]

I would be interested in data regarding the operation of vacuum on sap production, for the case where the pump is running continuously, versus pump turned off when sap stops running (lines frozen). My specific question is related to small diaphragm pumps such as Shurflo or the Bosworth Guzzler, but this could also apply to larger pumps. With the larger vacuum systems, folks typically leave the vacuum running 24/7 during the season, except when there is an extended freeze. Diaphragm vacuum pumps are typically turned off when sap is not running (at night), to conserve battery power and/or to avoid damage to the diaphragm during extended running dry or running with potential ice buildup internally. Manufacturers often recommend that the pumps should be turned off and drained in freezing temps. I would be curious to know if there is a sap yield penalty if the pumps are turned off at night, if so how much. It is often not possible to keep the pump warm at night. Perhaps this has been studied before, if so a link would be appreciated. Thanks.

Dave

[DrTimPerkins]

Funny that Dr. Abby and I were just talking about this earlier today.

[berkshires]

This is probably a very basic question, because I'm a total novice. What are the factors that you can use to guess relative sugar content of a tree. I have way more trees on my property than I have time or boiling capacity for. So I want to pick the best ones. The most obvious factor is:

- Crown size.

But what else? Is there any relation to things like:

- On a steep hill, the direction the hill is facing? Like, will a north-facing tree have lower sugar than a south-facing tree?
- Size of the trunk?
- Color of the leaves? Will a tree that always has brown leaves perform better or worse than one with bright orange leaves?
- How late the tree holds onto its leaves? Some trees seem to drop their leaves at the first sign of frost, while others still have bright green leaves.
- Anything else?

Thanks!

Gabe

[DrTimPerkins]

What are the factors that you can use to guess relative sugar content of a tree?

It is difficult to predict the SSC of a tree. Big trees with wide crowns growing on good soils are best, but there isn't a good way to distinguish one tree from another growing side-by-side. Best approach is to test them with a refractometer (using appropriate technique). Just know that SSC can vary a lot over a season, so best to measure groups of trees all on the same day (and within a few hrs of each other) if possible.


- Crown size.

Slight relationship, but difficult to measure, so diameter (dbh) is used more frequently. In general though, canopy trees will tend to have a slightly larger SSC than understory trees.

- On a steep hill, the direction the hill is facing? Like, will a north-facing tree have lower sugar than a south-facing tree?

No relationship has been demonstrated.

- Size of the trunk?

Only in terms of whether it is a canopy tree or not. Larger trees tend to be canopy (dominant or codominant) trees, so SSC tends to be higher.

- Color of the leaves? Will a tree that always has brown leaves perform better or worse than one with bright orange leaves?

There has been some research showing that trees that tend to be more "red" tend to have somewhat higher SSC.

- How late the tree holds onto its leaves? Some trees seem to drop their leaves at the first sign of frost, while others still have bright green leaves.

Green leaves lower, yellow moderate, red higher, but the relationship is fairly low.

- Anything else?

Nutrition. Good nutrition, particularly calcium (maples really like calcium) tends to produce more chlorophyll, more photosynthesis, more growth, higher SSC and more sap. But keep in mind that too much is not good either.

We do have some data and have been doing some analysis for a few years on what environmental or biological variables tend to be associated with higher SSC. Lots more work to do on this, but in general, there is a genetic maximum potential SSC trees can attain (which is quite variable from tree to tree). Once you stray outside the "norm" for weather or stress factors (drought, hot weather, etc), then you tend to drive SSC downward from the genetic potential.

An "oldie but goodie" on SSC can be found here http://www.uvm.edu/~uvmaple/sapsugarcontentvariation.pdf Work by Dr. Fred Taylor (deceased), one of the founders of the UVM Proctor Maple Res Ctr.

[eagle lake sugar]

I was giving a sugaring class in adult ed and the guy monitoring the classes was from the cooperative extension I believe. He asked a good question that would be a great study. He mentioned how they use fertilizer spikes for various trees they plant and the amazing difference it makes in tree health, crown etc. He asked if I considered doing that for my maple trees. It seems like you could fertilize trees close by to others and tell very easily if there's a difference in crown size, sugar content, etc.

[Jeff E]

Tap hole healing and how it relates to sugar and sap production the following year.
If a 5/16 tap hole heals by Sept does that indicate tree health that predicts higher sugar the following season.
Or
If you go to tap a tree and the tap hole hasn't closed 50% from the following year, should I skip the tree and remove the stress for a year.

Similarly, does crown die off indicate significant stress and call for 'resting' the tree for a season---or make firewood.

[DrTimPerkins]

Interesting

[Maplewalnut]

Would like to see a study on replacing taps vs time til next tapping. In other words can I replace taps now and have the same result in tap hole sanitation or would it be data significant to change out say in Nov/Dec. obviously a change out now has duration and warmer temps working against you when considering bio growth

Mike

[berkshires]

Thanks Dr Tim, this is really great info!

Cheers,

Gabe

[Aaron Stack]

Has there been any research on the effects of localized water quality issues on sugaring? Some examples like a high sulfur content in the water (like in the Moosehead Lake Maine area - filters required for drinking water at the cabin we rent in the summer) , having a property next to but uphill from a transfer station (nice piece of land for sale), or in areas where perfluorinated carbons, better known as PFAS had been used in firefighting foam (this is a local issue impacting fresh water drinking wells surrounding our National Guard Airbase now), or even former farming pastures.

I've Googled a bit and can't seem to find anything about that sort of thing. I assume the impact would be a negative to sugaring, but with all the boiling perhaps that removes the issues normally associated with drinking it straight.

[ecp]

I have 2 questions. 1 is related to equipment and the other related to production.

Equipment related question.
Has there been a test done using water to water heat pumps relating to increased productivity in the RO field? Raw sap goes through an RO faster when it is warmer, so it would make sense that if water (raw sap) was pre-heated with a heat pump using the rejected heat to cool the concentrate you could both increase the production time of your RO and by volume have cooler concentrate than the raw sap coming in. This may sound like an odd question, but if the manufacturers could offer this as an add on to any RO than for the people that are outgrowing there current RO would have another option that would be less expensive than buying a larger on. Specifically in this study I would be interested to see if spoiling time changes, and what the bacterial growth would be. With the technologies in the heat pump field over the last 10 years this may end up being a savings in electricity as well (it is on paper but real world testing always proves a little different)

Production related question.
I understand that high vacuum is proven. To my understanding (please correct me if I am wrong) is because it changes the barometric pressure in the tree. Has there been a study done on varying the vacuum level throughout the day to see if increasing and then reducing the barometric pressure in a tree actually changed production?

[DrTimPerkins]

Has there been any research on the effects of localized water quality issues on sugaring?

It depends almost entirely on the substance in question. PFAS compounds don't seem to be taken up by trees. Neither is lead. Some pesticides are translocated systemically in the tree. The best answer is that it depends upon what substance/pollutant you are referring to.

Turns out this response is my 5,000th. I'm no Dave Klish (maple flats), but seems like a good bit to me.

[DrTimPerkins]

Equipment related question.
Has there been a test done using water to water heat pumps relating to increased productivity in the RO field?

I assume you mean heat exchangers? If so, we did some work several years ago using hot water off the Steam-away to preheat incoming sap. It raised the efficiency by a good amount. I do know some sugarmakers who have used heat exchangers to preheat sap before the RO and thought it helped a good bit. There is no question that it would help increase RO efficiency, and if used on the concentrate side, would cool the concentrate. The real question is whether the additional cost would justify the expense of the exchanger and the added plumbing required. Probably not for small-moderate producers, but for larger operations it might well be worth it. But the answer to your specific question is "no", I don't know of any research on the subject pertaining to sap/concentrate specifically.


Production related question.
I understand that high vacuum is proven. To my understanding (please correct me if I am wrong) is because it changes the barometric pressure in the tree. Has there been a study done on varying the vacuum level throughout the day to see if increasing and then reducing the barometric pressure in a tree actually changed production?

Sap moves in response to pressure gradients, from areas of high pressure to areas of low pressure. You can think of it as water running downhill. The steeper the gradient, the faster the sap (or water) will flow. By artificially increasing the gradient from the inside of the tree to the outside of the tree (within the tubing system using vacuum), you make the sap run out faster and can pull more of it out within a flow period. Pulsation of the pressure (increasing and decreasing pressure within the tree or the tubing system) will not produce any beneficial effect.

Vacuum is a weird thing. It simply means "below atmospheric pressure", and so we have to phases we think of: pressure above atmospheric (which the tree is in immediately upon thawing), which is thought of in PSI, and vacuum, which is pressure below atmospheric, measured in inches of Hg, but really in terms of physics there isn't that distinction. It is simply pressure on a continuous scale. The pressure in a tree is high right after thawing, and falls to a lower pressure as the sap flows out until it equilibrates with the external pressure...either the pressure of the atmosphere (for gravity collection) or the pressure in the vacuum tubing system.

The actual difference in gradient is important as this will dictate how much sap will flow out after a sufficient period of time. If the vacuum is high enough, sap flow might not stop, but you'll enter a phase where water can be pulled from the ground, into the roots, up the stem and out of the taphole. Sap sugar will steadily drop when this happens. The strength of the vacuum also influences flow RATE. This comes into play when you have periods during which the thaw is not long enough to fully equalize the pressure in the tree to the outside. Another analogy -- a garden hose. Turn it on a little (low pressure) and it'll take a while to fill a tank. Turn it on full blast (high pressure) and the tank will fill faster. If there is a steep gradient (because of vacuum), then the sap will flow out faster during a short thaw and you'll get more sap before the spigot is shut off by a freeze.

Finally, given a long enough flow, with vacuum, the pressure on the inside of the tree will get low, that is...get below air pressure, and you can have vacuum develop WITHIN the tree. This isn't bad for the tree -- the xylem (wood) in trees is under negative pressure most of the time when there are leaves. But "vacuum" or pressure below atmospheric does "get into" trees on vacuum systems if the thaw is long enough. This probably actually enhances water uptake during the freeze period.

[Aaron Stack]

Great to hear on the PFAS compounds - I won't have to change my plans for next year.

[DrTimPerkins]

Great to hear on the PFAS compounds - I won't have to change my plans for next year.

Note that I cannot certify that there is no PFAS in your or any particular syrup without it being tested, however in the testing that the Vermont Department of Environmental Testing did of maple syrup made from trees within the area of concern, PFAS was below the detection limit.

https://vtdigger.org/2016/04/13/maple-syrup-not-affected-by-pfoa-contamination-tests-show/

https://dec.vermont.gov/sites/dec/files/co/pfoa/documents/Maple.syrup_.results.N.Benn_.pdf