tree growth and tapping small trees

[DrTimPerkins]

does the hole grow together on the inside below the cambium layer?? it doesn't stay hollow does it? I started tapping here 4 years ago, I think got hit bad ice storm 98'. I know many have bad culls and some are hollow so hitting bad Area is very possible and kinda what im thinking.

The cambium layer is between the wood and the bark. Phloem (inner bark) grows toward the outside. Xylem (wood, what we see as an annual ring) grows toward the inside. The cambium starts to grow from the outside of the hole inward. Typically 2-3 "fronts" grow from the sides and merge near the center, and eventually grow together. After that, new wood (and bark) will develop on the outside of the hole. The taphole itself doesn't really fill in, although sometimes you'll see what looks like a wood plug near the outer edge of the taphole. This is actually bark from where the cambium curled in, so the tissues are somewhat inside out. Once the hole seals up, that growth stops so the hole doesn't completely fill in.

The areas around the taphole (mostly up and down) that turn brown is from compartmentalization, a natural wound response of the tree to inhibit the growth and spread of diseases inside the tree. The affected area (brown wood) is rendered non-functional in that it will no longer conduct sap and is no longer useful for storing sugar.


while on subject of wounding, I have many 4-8 inch maples on edge of my meadow, im going to tap some using 5/32 adapters. im assuming a 1/2 or 3/4 inch hole would not hurt a tree this size. seems to me tapping smaller trees would not hurt them since they are so robust and would only drill in a proportionate distance relative to the diameter. whats your thoughts on this??

Depends what you mean by "hurt". A small taphole will make a small wound. The concept behind sustainable tapping is to never render non-functional (no sap movement, no sugar storage) by tapping more wood than the tree can grow back in the next growing season. However the other side of the coin is sugar removal. If those trees have good sun exposure, you're probably OK with a very small taphole. Small trees in the understory of other trees are a different story. They are very light-limited, and so any amount of sugar you remove from them is going to have some effect in terms of slowing their growth.

[spud]

Thank Dr. Tim. So if a person has a woods full of 6 inch trees with no large maples blocking their sunlight would they be ok to tap? Would you be doing more harm then good? Lets say only tapping 1 1/2 inch hole using 5/16 spouts. If a person uses longer drop they could cover a larger area of the stem while waiting for the older hopes to heal and newer wood to from in that area. I thought I read that after 7 years the tree would grow enough to tap over the same area again. Not all trees grow at the same rate though so I am not sure if this is true. This is why I asked you a few years ago about tapping below the lateral line. I know you have done studies on tapping 2 inches above and below and have found no real difference in production. What about tapping 12 inches below a lateral line? If a person used CV2 spouts not allowing sap to flow back in to the tap hole would high vacuum allow for the same production numbers? Even if you had to use a 60 CFMS pump for just 2000 taps. If its possible then a person might be able to tap a 4-5 inch tree.

Spud

[DrTimPerkins]

If its possible then a person might be able to tap a 4-5 inch tree.

Hi Spud....Thanks for putting me on the spot with this question. :lol:

First off....tapping guidelines are generally GUIDELINES. They are your trees and you can do whatever you like (unless you're certified in some way that restricts that....like organic certified, etc.). Second, we are in the midst of a complete review and a lot of research looking at tapping guidelines from a number of different perspectives. Most of the time, guidelines only consider wounding and recovery as a function of tree growth. It is important (particularly with small trees) to also consider the question of how high rates of removal of carbohydrate reserves affects small (and large) trees to get a complete understanding of the issue.

So....if you're asking....under some conditions would it be appropriate to tap a 4-6" tree? My answer is....maybe. Would you get as much sap? Probably not. If this were done, you'd definitely want to do it only in trees that were growing fast and had good crown exposure to the light (so NOT trees in the understory), use 5/16" (or smaller) spouts, long droplines, and utilize the tapping band both above and below the lateral line to spread out the wounds. I'd also suggest NOT tapping your future crop trees in this way, but let them grow unimpeded.

SO BEFORE ANYBODY THINKS THIS IS A RECOMMENDATION....IT IS NOT! I'd suggest you all go to the UVM PMRC website and read what you can about tapping guidelines and play with the "Tapping Zone Model" spreadsheet.

I guess my other concern is that people might think...gee, I've got a whole section full of thick dog-hair trees (3-5" dbh), so I might as well tap them. Truthfully, I don't have a problem with people doing a little "thinning with a tapping bit", but the reality is that you will do a WHOLE LOT better if you get in there and thin with a chainsaw to release some good crop trees and let them grow WAY faster than they will if they are that crowded.


I know you have done studies on tapping 2 inches above and below and have found no real difference in production. What about tapping 12 inches below a lateral line?

Before anybody misunderstands....we looked at (and will continue this study) tapping 2 feet above (a normal dropline) versus 2 feet below the lateral line as a way to increase the size of the tapping band. So far it appears to be a reasonable solution to finding good wood in certain circumstances, but we need another season to be sure there aren't any (as yet) unforeseen problems.

[Ray_Nagle]

Dr. Tim,

What percentage of a tree's sap/carbs are we stealing when we tap it? One percent? 30 percent? I'm assuming it depends on the diameter of the tree, but is there a general number you go by?

[lpakiz]

Could a person tap in the exact same ""grain" of a previous tap, only 2 feet above or below an old stain and get normal sap flow?
Does the "dead wood" zone just stop at the end off the stain, and the wood above and below become sap-bearing?
Would vacuum help this work?

[DrTimPerkins]

Could a person tap in the exact same ""grain" of a previous tap, only 2 feet above or below an old stain and get normal sap flow?
Does the "dead wood" zone just stop at the end off the stain, and the wood above and below become sap-bearing?
Would vacuum help this work?

If you are outside the stained (non-conductive) zone, then you would get normal sap flow. Vacuum always help to move sap around in trees by creating a larger 'driving force". Think of it as wanting to move a trailer. Would you rather pull it with a Prius, or a 1-ton truck? You'll pull it a lot more efficiently with the truck.

A related question is whether or not an area of stain from a taphole (or from several) in a section of a tree creates any sort of resistance to sap movement through that segment? Are the wounds that are created (the stained wood) roadblocks that slow down the movement of sap or make it more difficult for sap to move. We really don't know...but it is something that we will be looking at over the next few years by building a test device where we can "suck" water though a section of stem and see how much the stem hydraulic conductivity changes with increased wounding. The work is funded in part by a donation from the Chittenden County (VT) Maple Producers Association (thank you very much). So ask me about this again in about 3 yrs.:)

[DrTimPerkins]

What percentage of a tree's sap/carbs are we stealing when we tap it? One percent? 30 percent? I'm assuming it depends on the diameter of the tree, but is there a general number you go by?

Excellent question. Before we started our recent work, the last time this was investigated was by Dr. Jones (from the "Jones Rule of 86") back in the early-1900s. At that time the estimate was about 4-7%, but there wasn't much about how they arrived at that number.

It turns out that size is very important, but the way you collect sap (gravity or vacuum) is also important in determining the total amount of sugar you remove from the tree.

You can think of the amount of sugar removed from the tree for maple syrup production as an "interest rate" or tapping "tax." You are asking the tree to pay you a certain amount of it's sugar or "wealth", each year, over many years.

For a large tree (> 16" dbh) with good crown exposure, on gravity, you're getting about 0.5%. Same tree under vacuum, maybe 1%. Nothing to worry about.

For a tree right about at the minimum size for tapping (depending upon whose guidelines you use) of about 9" dbh, the interest rate is about 2% (gravity) and 4% (vacuum). This probably also doesn't negatively impact the growth of the tree in a major way (but may still have some detectible effect).

For a tree growing in the understory and about 6" dbh, the tax rate is about 5.5% (gravity) and nearly 12% (vacuum). This is getting to the point where it WILL affect the growth of the tree, especially those in the understory not getting much sun. The smaller you get, the faster the interest rate goes up.

So you can see, this is a VERY retrogressive tax. The less sugar (wealth) the tree makes, the higher you are taxing it. Once the tree has a huge amount of wealth, the tax is negligible. But for those really small trees, that tax rate has a big impact.

[optionguru]

As a semi-retired stock broker I love the analogy. Thanks for the great explanation Dr. Tim.

[spud]

Thank you Dr. Tim for answering so many questions in one day. Get some sleep because we might have more questions for you in the morning.:)

Spud

[DrTimPerkins]

Thank you Dr. Tim for answering so many questions in one day. Get some sleep because we might have more questions for you in the morning.:)

Monday was technically a holiday, and yesterday was supposed to be a day off since Saturday was a maple conference all day. No rest for the wicked...so apparently I've been really bad. :evil:

[Ray_Nagle]

Thanks, Dr. Tim, for the excellent explanation. Good to know it's such a low percentage.

[blissville maples]

tim- good analogy with the "taxing" so your thinking anything above the 5-6% is probably affecting the trees growth/health? what about the 2-4% you mention detectible? meaning slow growth, small crowns, low sugars?? I agree with thinning versus tapping, many of these small trees stay alive and continue to crowd the others as ive seen. however, I only own 13 acres, and although probably in the 5-10 year range am hurting myself, it seems practical now at the moment. I have, hundreds of these trees, must be from a good seeding year since they all seem to be nearly the same size. 5 years ago I tapped about 10 4-5 inchers, filled a bucket in no time, but only one, they don't have much reserve compared to the larger trees. as I said I will be trying these waterloo 5/32, they are tiny almost pencil lead size hole, I cant see that creating much stained wood, and I am wondering if the area is so small that the tree actually heal across the hole and maybe be Somewhat conductive due to its small size that??? im going to cut one down to do some cross sections, this is very interesting to me. however, as in this sapling capping, how can there be any sugar in these trees after you pull the intitial sap out?? also interested in the new conductivity studies results.

good luck all, get ready going to come fast!!!!!

[ToadHill]

That would be Dr. Tim.