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Thread: Frozen ground and sap flow.

  1. #11
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    snow melt by tree.jpg
    This is why I believe the tree is thawing from the top down. You can see in this picture a 2" gap around the North side of the tree. It is the same on the South side too. The snow is 18" deep here on this tree.
    A good gauge of how deep the frost in the ground is, is by the thickness of the ice on a lake. The lake too has snow cover.
    Grave diggers in Minnesota have it the worst, especially if they're digging in clay. North Dakota is permitted to have Spring funerals due to the difficulty of digging through 4+ feet of frozen ground.
    Last edited by billschi; 03-21-2018 at 07:12 PM. Reason: Additional information.

  2. #12
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    The ground near the base of this tree is frozen hard, and it is running well. We have had years without snow and extended subzero nights, and our sugar maples are still here. When you say that the root tissue is not cold tolerant, what happens when they freeze?

    https://youtu.be/T9SmjegLXaQ

    Maybe a bit further out under the snow the ground is thawed, but in my experience, it is frozen too. I can clear a bit 5 or 10 feet away from the stem and check tomorrow.

    FYI, still snow on the surface and 18 inches of ice on the lake here.
    John
    2x8 Smokylake drop flue with AOF/ AUF
    180 taps on sacks
    75 on 3/16 tubing with shurflo
    Eden Prairie, Minnesota

  3. #13
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    Quote Originally Posted by billschi View Post
    A good gauge of how deep the frost in the ground is, is by the thickness of the ice on a lake. The lake too has snow cover.
    Grave diggers in Minnesota have it the worst, especially if they're digging in clay.
    Not to be argumentative, but a lake is not a forest. A graveyard is not a forest. A parking lot or road is not a forest.

    A lake has "turn-over" in the fall. Water cools and sinks, warmer water rises. Eventually it is all close to freezing. The coldest water just near freezing actually expands, so it rises and then freezes into an ice layer. Nothing comparable happens in forests. Snow falling on lake ice doesn't make a huge difference. There isn't much of any heat coming from the liquid below.

    A graveyard is open land...very little leaf-litter to insulate the ground and the soil is fairly disturbed in areas. It will freeze much more readily than forest-land.

    Soils in woods tend not to freeze very much unless they are disturbed (you log the area or run your tractor over it) or if you have sub-zero weather with no snow cover. Only the very upper layer. This is true in Vermont, it is true in Alaska (permafrost is a totally different thing), it is true in Minnesota. Any freezing tends to be confined to the upper layers, soils don't typically get really cold, and any freezing is typically transient.

    If you look through the literature, you'll find dozens of papers about forest soils and temperature profiles. I've measured soil temperature since I started additional science training in high school, as a technician, during my Ph.D. and for 20 yrs since. Yes, forest soils can freeze, but it is not the typical situation for them to freeze to deep levels or to remain frozen for a long period of time.

    In the photo, the snow melts from around the base of the tree because the tree is dark and absorbs solar radiation. This is re-radiated as heat, which melts the snow. The tree is not generating the heat internally....they don't do that. Roots don't normally need to thaw...because usually they are not frozen to begin with.
    Dr. Tim Perkins
    UVM Proctor Maple Research Ctr
    http://www.uvm.edu/~pmrc
    https://mapleresearch.org
    Timothy.Perkins@uvm.edu

  4. #14
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    Quote Originally Posted by RileySugarbush View Post
    The ground near the base of this tree is frozen hard, and it is running well. We have had years without snow and extended subzero nights, and our sugar maples are still here. When you say that the root tissue is not cold tolerant, what happens when they freeze?
    Your video shows the soil surface. Yes, there can be frost near the top, and frost can penetrate during times of no snow cover, but typically the soil below 6-12" down is, at worst, just above or just below freezing.

    Cold tolerance in this case doesn't mean that they can't stand freezing, just that they can't stand to get really cold (like air temperature and above-ground stem/branch temperature). Maple cold tolerance is difficult to quantify simply, but at temperatures less than 15 deg F, there is considerable loss of root biomass. This compares to cold tolerance of shoots/buds/stems of -40 deg F.

    IF the soil is truly frozen, where is the water for sap recharge coming from?

    FYI, still snow on the surface and 18 inches of ice on the lake here.
    There is snow on Pluto too, but like the ice/snow on the lake, it has little to do with what is happening in the woods.
    Dr. Tim Perkins
    UVM Proctor Maple Research Ctr
    http://www.uvm.edu/~pmrc
    https://mapleresearch.org
    Timothy.Perkins@uvm.edu

  5. #15
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    OK. That makes sense. I haven't done any drilling to check depth and I haven't measured soil temps. I did go to that same tree this morning, about 8 feet away in undisturbed snow. The soil surface is frozen there. The maul bounced off like before. In some areas there is surface water from snow melt, which around here is the indicator that thesis is still frozen. One day, all the collected water we have been slogging through is just gone, and we have entered the next season in the woods: Mudtember

    So how deep is the root mass that we are concerned with?


    "IF the soil is truly frozen, where is the water for sap recharge coming from?"

    I am thinking that when the surface is still frozen as I see here, that the soil is thawing out from the bottom up, especially in snow covered areas, and that as the lower roots are thawed they contribute sap. Around here that is just now happening.....Finally!. Yesterday many trees started running well, including the one I was pounding next to. Others are still quiet. In suburbs closer to Minneapolis, the backyard trees are reported to be running very well. Heat island effect to some extent, good snow cover in the back yards, no kids packing down the snow in the woods with snowmobiles....

    In this area, really cold winters and sometimes not a lot of snow, I guess the maples root near the surface suffer and most are further down in the more moderate temperatures.



    John
    2x8 Smokylake drop flue with AOF/ AUF
    180 taps on sacks
    75 on 3/16 tubing with shurflo
    Eden Prairie, Minnesota

  6. #16
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    Dr Perkins,
    Understand, I too am not trying to be argumentative. I'm just trying to wrap my brain around what's happening here. I know it's not important except as to know when will be the best time to tap. I have found some trees close to a low lying swampy area and the trees are starting to do well. Whereas the trees on a North facing hill are dry. The trees on a South facing hill now have minimal drips. That's what got me to thinking about frozen ground. So maybe I will put taps out in 3 phases next year.
    I like your explanation and I'll take my ice auger out and try a few locations. Since it will be a 6" hole, I will bring a meat thermometer and check temperatures at different depths. I truly appreciate your input.
    Also another question for you. If I put taps out 2-3 weeks before the sap runs, have I lost full potential of the sap run? I mean, is there a drop in potential production because the tree is trying to heal itself even before the run?
    Last edited by billschi; 03-22-2018 at 03:27 PM.
    2016- 32 taps, 3 1/2 gallons
    2017- 150 taps, 13 gallons after building an evaporator
    2018- goal is 240+ taps. 20+ gallons.
    2018 Reality- 235 taps, 5 gallons of syrup. Average 50 birch taps and 3 gallons of syrup.
    2019- 180 maple taps, 20 gallons of finished syrup.
    ~ 160 birch taps, 13 finished gallons of syrup.

    Latitude 47.278150

    www.facebook.com/livingoffmyland2015

  7. #17
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    Sounds good. Once you drill a hole, if the temperatures are low enough, it'll start to freeze from the edges in. In monitoring, a small pit is dug, the probes inserted into undisturbed soil in the side of the hole, and the hole refilled. There are other methods as well. I think the first method I learned was to auger out a small hole, put a PVC pipe in it, then a piece of tubing filled with colored water (Kool-Aid). Where the freeze line is will show very differently. Even in that situation (very cold site in a spruce forest), the soil didn't freeze much below the litter layer.

    As soon as you drill the hole the tree will start to "wall off" the wound. The wound response (how vigorously the tree walls off the area) is proportional to the amount of microbes the tree senses in the area, which is why very good spout/drop sanitation is critical in getting high yields. If you're not using vacuum, you only want to tap as short time before the trees will start to run. With open spouts, you'll get about a month of sap flow before it stops. With good sanitation and vacuum, we can get 8 weeks or more.

    Below are a couple of graphs of soil temperature with depth over time. The first is from Dale Nichols, USDA Forest Service in northern MN (5 yr average I think). The second is from northern VT (10 yr average) and done by the USDA NCRS. At PMRC we have decades of soil temperature monitoring. March-April tends to be when we have the coldest soil temperatures, which are right around (just above or just below) the freezing point. Once you get more than a ft down, the soil in forests tends not to freeze except in unusual circumstances (no snow).

    Capture1.jpg

    Capture2.jpg
    Last edited by DrTimPerkins; 03-23-2018 at 08:34 AM.
    Dr. Tim Perkins
    UVM Proctor Maple Research Ctr
    http://www.uvm.edu/~pmrc
    https://mapleresearch.org
    Timothy.Perkins@uvm.edu

  8. #18
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    I've been getting some flow this past week week on about 40% of my taps. The south facing low ground taps were doing well, maybe 1/2 gal/day. Lat night our temps went to about 26 degrees and today was about 56. To my surprise, there is no flow. Do the trees stop flowing at certain temps during the day?
    2016- 32 taps, 3 1/2 gallons
    2017- 150 taps, 13 gallons after building an evaporator
    2018- goal is 240+ taps. 20+ gallons.
    2018 Reality- 235 taps, 5 gallons of syrup. Average 50 birch taps and 3 gallons of syrup.
    2019- 180 maple taps, 20 gallons of finished syrup.
    ~ 160 birch taps, 13 finished gallons of syrup.

    Latitude 47.278150

    www.facebook.com/livingoffmyland2015

  9. #19
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    There will be no good flows until there is a recharge.
    Dr. Tim Perkins
    UVM Proctor Maple Research Ctr
    http://www.uvm.edu/~pmrc
    https://mapleresearch.org
    Timothy.Perkins@uvm.edu

  10. #20
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    Quote Originally Posted by DrTimPerkins View Post
    There will be no good flows until there is a recharge.
    Isn't the recharge a freeze at night? I'm curious if it gets down to 26 at night and 60 during the day, does the sap stop flowing after say, 50 degrees during the day?
    2016- 32 taps, 3 1/2 gallons
    2017- 150 taps, 13 gallons after building an evaporator
    2018- goal is 240+ taps. 20+ gallons.
    2018 Reality- 235 taps, 5 gallons of syrup. Average 50 birch taps and 3 gallons of syrup.
    2019- 180 maple taps, 20 gallons of finished syrup.
    ~ 160 birch taps, 13 finished gallons of syrup.

    Latitude 47.278150

    www.facebook.com/livingoffmyland2015

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