Peter Wohlleben, professional forester and science writer in Germany, explained how snow loads can seriously harm trees.
From his book “The Hidden Life of Trees” – “The pressure from above is simply too great. Such breakdowns mostly happen in the months of March and April, when the snow is transformed from feather-light fluff to dead weight.” He estimates the point where snow becomes dangerous by analyzing the clusters of falling flakes. When clusters are about the diameter of a quarter, the tree safety situation becomes critical.
This snowflake physical condition is a trait of wet snow, which holds a lot of water and is very sticky. Rather than falling through the tree branches, such wet snow adheres to them, forming thick, heavy layers.
According to the American Meteorological Society’s glossary, “Spring snow, also called corn snow or granular snow, is a coarse, granular, wet snow resembling finely chopped melted ice. It is generally found in spring.”
Wet snow falling on tall, sturdy trees can break branches; the problem is even worse on immature trees. With lanky trunks and small crowns, they are either broken by snow loads or bent over so far that they never right themselves. Smaller trees, including saplings, are usually supple enough to rebound from snow piling up on tiny branches.
On March 23, much of the Northeast experienced heavy snow, air temperatures locking in at the freezing point. A lot of branches weakened on trees in our yard, both coniferous and deciduous. Fortunately, few of our trees lost branches.
Some refer to this dense, soggy gift of nature as “heart attack snow.” But it still offers some pluses; old timers often refer to spring snow as “poor man’s fertilizer.” This is because snow, like rain, contains nitrogen (N) as well as minute amounts of phosphorus (P) and sulfur (S). The wetter snow washes these elements out of the atmosphere, depositing them on fields, yards and gardens.
Research shows that the airborne presence of these plant nutrients has been increased by byproducts of industrialization (emissions). Still, these are plant nutrients, free to crop growers.
Atmospheric S has decreased in recent years, due mostly to the effectiveness of the federal Clean Air Act. Earth’s atmosphere is roughly 78% N, but that N is relatively insoluble in its couplet (N2) form. Pollutants like nitrous oxide – a greenhouse gas – merge much more readily with snow, and even water, than does S.
According to scientific field tests, the amount of N accompanying precipitation each year ranges between 2 and 12 lbs./acre – with an average value of 7 lbs. being presumed for soil nutrient calculations. Scientists believe that snowflakes pick up more N than raindrops. Because snowflakes are more crystalline in structure than water is, they tend to combine more readily with airborne chemicals.
The amount of N present per acre from snowfall depends on location and annual snow accumulation. An average annual N deposit of 7 lbs. doesn’t seem like much compared to commercial N applications exceeding 100 lbs. (common on each corn acre). But the key word is “free,” making this source of N a pleasant side benefit, assuming not too many tree branches break.
While rain and lightning also contain N, snow boasts several agronomic advantages over the other two free sources. First, snow stays around for a while, setting free its nutrients in a slow-release manner. Snow also helps insulate plants from temperature fluctuations, which can cause heaving and related problems from frequent freezing and thawing. Thirdly, snow makes small plants like strawberries less visible to hungry critters. Fourthly, snow helps prevent plant growth from starting too early. Lastly, snow, unlike heavy rainfall, doesn’t leach nutrients away from plant roots.
Residents of Canada’s Maritime provinces (which many consider an extension of our Northeast) divide spring snowfalls into three categories. First comes the “robin’s snow,” occurring just after the robins migrate back. Then the “smelt snow” happens when the smelt are “running” in the rivers near the coast. Lastly, these Canadians recognize “poor man’s fertilizer,” delivered by the snow that lands on freshly plowed land in early spring.
The economic benefit of snow-borne free N becomes even more pronounced when framed by the chaotic crop nutrient supply/demand situation confronting growers. I’ll give the per ton cost for urea at FOB Cincinnati for March 7 of $430/ton. The N level in that commodity is 45%. This means that 1 lb. of N in urea costs $0.478 ($430/900 lbs.).
The take-home message here has several parts. First, figure how much fertilizer you can afford. Get that fertilizer ordered. If you haven’t done so in the last three years, sample soils so you can accurately apply amendments per recommendation. Use nature’s contribution as part of the cake, not just the frosting. Apply lime by recommendation, accepting that lime price increases have been comparatively negligible. Lastly, increase perennial legumes in rotations. Typically, their N-fixing bacteria colonies parcel about 10 times as much N as what nature piggybacks on spring snowflakes.
No branches broke, hitting power lines in or near our yard. But somewhere in our NYSEG power zone, at about 4 p.m. on March 23, all electric customers got blacked out. Folks without generators (like the Hartwick Reidheads) didn’t get their lights back on until 11 p.m. Our house is well-insulated, so things didn’t cool off too fast. Our snowblower labored hard, getting rid of seven inches of slushy mess. Using a couple Passover candles, we heated enough water for a cup of tea in 30 minutes. Outdoor temperatures didn’t start plummeting, mercifully, until power was restored. At dawn Sunday morning, our remote-sensing thermometer read 13º F, one degree below sublimation – when ice evaporates directly into water vapor without first melting.
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