A walk in the woods: Atypical trees

A nature enthusiast ventures into the forest, traversing its woody arms for several minutes and experiences a sense of reverent calm, with the impression of having abandoned civilization in that span of time. Suddenly something catches his attention: the trees.

There are hundreds of them, as would be expected in any forest, but these are strange. They are twisted, rather twisted. It doesn’t make much sense, after all most grow upwards. And what about those others? Why does it look like they’re about to collapse?

The Dancing Forest

The Dancing Forest is located on the Curonian Spit, a 98 km long sand bar that separates the Curonian Lagoon and the Baltic Sea. Officially, this isthmus belongs to two nations: the southern half to Russia (Kaliningrad Oblast) and the northern half to Lithuania.

In this forest, the pines were planted in the 1960s as part of the plan to stabilize the soil and protect the sand dunes. But as the stems grew, the pines drew strange shapes, twisting and curving just inches from the base. It is one of the most atypical phenomena that the human being has seen in this type of reforestation, comparable to other cases such as that of the Alticane forest, or the ‘drunk’ trees of the taiga. However, unlike these two examples, the reasons for their cause are not entirely clear.

bosque — *1. Examples of the Curonian pine forest. Source: greentourbaltic.com*

There are numerous theories about it. Some point to climatic elements such as the wind or a time of heavy snowfall that hindered the growth of pine trees. Others, related to history, focus their attention on the Nazi occupation during World War II in Königsberg, blaming the Germans for the poisoning of the forest floor before leaving that place. Of course, we also have local legends about witchcraft, energy concentration, and pagan dances in the Middle Ages.

Evetria

At the moment, the most reliable explanation comes from Ecology. It appears that a type of caterpillar known as ‘evetria’ (Rhyacionia or Petrova resinella) may have affected several of the specimens during their growth stage, resulting in the characteristic deformation that we see today. Larvae cause damage by feeding on pine buds, causing sinusoidal deformations, since they feed only on the tissues on one side of the bud, leaving intact those on the other side. That is why the yolk initially twists to the damaged side and when growth recovers it regains verticality, adopting that shape.

The most sensitive trees to this pest are those of repopulation, since they are usually very young (between 4 and 15 years of age). In addition, the soil that accompanies the coniferous forest stands tends to be quite poor in nutrients, especially in the case of a sand bar that separates two bodies of salt water and makes it difficult to capture fresh water. These factors weaken the pine trees’ ability to fight the plague, and make this hypothesis sound.

Drunken Trees

Unlike most forests, trees in the Canadian and Siberian taiga do not always point in the same direction. This image might give the impression that the ground has been violently shaken, and the trees are about to collapse. Indeed, the origin of this phenomenon is in the ground, but no sudden force has destabilized the verticality of the trees: it is permafrost.

bosque Alaska — *2. ‘Drunken’ trees in Alaska. Source: nps.gov*

Permafrost

Permafrost is a term meaning ‘permanently frozen’, and is used to define soil or rock –including ice and organic matter– that remains below 0° C for at least 2 consecutive years. It represents 14% of the Earth’s surface and it is a permanent freezing layer whose thickness varies from a few meters to a hundred, although there are extreme cases where it reaches a thousand meters, such as in Yakutia, Russia.

In summer, a thaw occurs in what is called the ‘active layer’ (or ‘mollisol’), that is, in the upper horizons, whose thickness is 1 to 4 m. In winter, the active layer freezes again, and these seasonal changes cause the soil to contract and expand.

These drunken trees are located in the sub-arctic regions of the planet where boreal forests have grown on the permafrost layer. Conifers predominate, whose roots are not capable of traversing the underlying frozen ground and must expand horizontally on the surface. This limitation is a problem for the tree, since its stability is compromised in the thawing months of the active layer, and many end up tilting irretrievably.

CO₂ and methane deposits

In addition to this unique process, the most worrying is the retreat of permafrost towards high latitudes as a consequence of global warming that we have been experiencing for the last century. The melting of the thinner permafrost layers is releasing the deposits of organic matter and greenhouse gases accumulated over millions of years. It is a volume that represents 50% of the carbon available in the world, or four times the amount of carbon released into the atmosphere since 1850. Scientists have been warning for years of the irreversible consequences that could trigger a ‘snowball’ effect in the global temperature increase that we are already suffering.

The twisted trees of Alticane

During the 1940s, residents of the tiny town of Alticane in Saskatchewan Province, Canada, observed a rarity in an aspen forest (Populus tremuloides) growing on the edge of a farm field near Hafford. The specimens had a crooked architecture, as if the trees were unable to grow vertically.

For a long time, the inhabitants have speculated on the cause of this anomaly: soil contamination, effects of a meteorite that hit the area, aliens … There are even jokes about a lawyer who was buried there, which is why the trees are so twisted.

Alticane bosque — *4. The crooked aspen of Alticane. Source: tourismsaskatchewan.com*

Although it is true that environmental conditions, such as wind and salinity, may influence the growth of poplars, there is no evidence that the Hafford phenomenon is related to any of them.

Observation and conclusions

In fact, the University of Manitoba conducted a study in the 1990s to try to explain the particular shape of the Alticane aspen. Several samples from the twisted trees were grown in a controlled environment to isolate the climatic and edaphic variables. The result was that the new specimens developed the same twist in the branches as the original ones, so it was highly probable that the origin of this morphology was in a genetic mutation.

As compared to the usual Populus tremuloides, where the growth of the new branches is predominant in the terminal buds that guide the new shoots vertically, the Alticane’s show a weakening in this type of bud. That is why the axillary or lateral buds take over, being able to develop the shoots in all directions except upwards.

The gene that gives these peculiar characteristics makes it difficult for twisted poplars to grow vertically, which is a great inconvenience in terms of survival. In the plant kingdom, plants compete for sunlight, and the only explanation that these trees continue to exist is simply because they have had no other species to fight against.

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A walk in the woods: Atypical trees