Could a pine forest with year-round snowfall survive?

Question

I am trying to design an alien forest ecosystem. The forest looks like this (from Dreamstime.com):

The relevant difference between the real-life Swedish forest pictured and mine is that my world snows year-round, so the ground and trees are pretty much always covered in heavy snow. The temperature remains steadily between -25 to -10 degrees C all year. The surfaces of lakes and rivers are almost perpetually frozen, and the soil is very rarely visible.

This environment implies a number of challenges, most notably in how seeds for these trees could germinate or deep root systems could grow with dense snow and likely permafrost in the soil blocking their way. Many of these trees grow quite large, likely meaning the trees must break through the permafrost in order to build a strong enough root system to support themselves. It seems as though this is extremely difficult on Earth (not many trees in Antarctica).

I have had some left-field ideas for the trees to deal with this, such as spreading seeds through interconnected root systems already under the permafrost or literally impaling spear-like seeds through the permafrost from above. I would prefer if whatever mechanism it uses is mostly driven by the tree itself, as opposed to having an animal eat the tree's fruit and then burrow underground or something to spread it through droppings.

Is this winter forest feasible with these constraints? Are there any real-life examples of large, permafrost-breaking trees that I could draw off of?

Answer 1

A few notes.

You can have it snow all year, without snowing every day. The problem with snowing every day is the snow will just pile up, and gravity will compress it into an ice sheet. No matter how tall your trees are, eventually they will be buried. That is what has happened in Antartica; the ice sheet has an average thickness of two kilometers. Your trees are not two kilometers tall.

Also if it snows every day, photosynthesis is impossible. I'd make the snow intermittent, and I'd add some strong winds to "clean" the leaves (pine needles) so they can photsynthesize.

As for seeds: Not all plants grow from seeds. In particular, see here: https://www.sciencelearn.org.nz/resources/104-plant-reproduction-without-seeds

Plants that reproduce from asexual vegetative reproduction

New plants are sometimes made by asexual vegetative reproduction. These new plants have exactly the same genes as the parent. Some plants – like strawberries – have stems called stolons that grow out sideways above the soil, and new plants grow up along them. Other plants send out underground stems called rhizomes, which form new plants at a distance from the parent. Tubers (for example, potatoes) and bulbs (for example, onions) are also special underground structures that can grow into new plants.

This works for your trees, their roots are under the permafrost, so the rhizomes (underground stems) can spawn a new tree, and feed it, it eventually breaks from the parent and grows to break the permafrost. Just like plants that can crack concrete. Once it breaks through and starts photosynthesizing, it breaks from the rhizome of its parent, and grows independently.

This permafrost is probably cracked anyway (a path to grow through) by the adult trees growing; there is only so much surface area, so as the cross section of a tree slowly increases, the permafrost will be squeezed, push, and buckle. Maybe a good opportunity for the underground baby to push up and break out.

edit: P.S. You might want some sort of underground warmth that can cause the falling snow to melt. That way it wouldn't pile up as ice. Yellowstone Park comes to mind, an ancient volcanic crater that makes the ground warmer than the overlying air. So no permafrost at all. You could still have ground "seasons"; so a "summer" in which the atmosphere can still be -10c, but the ground is +10c so the snow melts and drains into the soil. If you want flowers, then this is the time to bloom: insects that live underground all year (similar to locusts) come out in vast swarms in the ground summer, brave the cold to collect the nectar (pollinate the trees), grow fat, mate and dig back in to lay their eggs for next year, and then starve to death keeping their eggs warm through the coldest part of the winter, leaving their body as food to nourish their hatchlings. (If you think that's weird, the mayfly has a 24 hour lifespan.)

The pollinated flowers is what triggers your trees Rhizomes, growing underground, to actually produce new trees that are not just clones of itself.

Voilá! Flowers, and sexual reproduction! (It's scifi, you don't have to get any more detailed than this, at least it isn't 'magic'.)

Answer 2

It is not feasible, because if it were snowing year-round, you would have a glacier. There is no forested ecosystem on Earth capable of growing on glaciers, for quite a number of reasons, and it's unlikely that one is even theoretically possible using Earth biology. At best, you could have lichens and mosses.

Answer 3

As you state, the propagation and germination of airborne seeds is conspicuous challenge in this environment.

Your trees need to be tall to have a chance of catching the dim light above the snow cover, and going throug it for the seed is practically impossible.

However, your trees can produce seeds by having some sort of underground fertilization, supported by their roots and maybe with the help of some burrowing creature.

When the roots of two different trees meet, they produce a seed which is then supported with the supply of vital juices by one (or both) of the parent trees in its growth above the snow layer, until it can independently starts to photosynthetize, at which point the bond with the parents is severed.

Answer 4

Hot springs or a geothermal source?

Perhaps to keep the ground warm, provides a microclimate for the trees where the snow doesn’t continuously compact on the ground.

Also not every day is a heavy snow day…

Answer 5

Minimum temperature (-25°C) is not a problem for plants, it's the maximum temperature (-10°C) that is. See my answer here: Extreme cold resistant flora, particularly the sections on Climate Classifiction and How does a plant grow.

Permafrost, as indicated by AlexP's comment, is permanently frozen, impermeable to plants. Permafrost occurs whenever the average yearly temperature is below the freezing point of water (0°C/32°F).

How deep permafrost begins depends on how hot your summers are; i.e. how much of it can melt from above before 'real' winter sets in, defining this as the time of the year after which above-freezing temperatures are rare: on Earth this can be as early as halfway through September for the coldest forested places.

How deep permafrost reaches depends on how much below 0°C that average temperature is. The earth has a gradient of around 12°C per km depth on average, but it's higher in geologically active places. At -18°C average temperature, your permafrost gets to be 1500m deep, far deeper than roots can go.

If you're looking for a pine forest (type Dfc/Dfd/Dwc/Dwd climate), you just have to have some amount of time where enough soil melts that the trees can establish deep enough roots. Typically it's about 50 days of consecutive above-zero weather or a maximum average monthly temperature of 10°C.

What you could do though, for an alien climate, is play with these values a bit, if you want a shorter summer. Make it more intense, and perhaps rarer.

In that case, here's a way to do this:

Multi-year winters

First, your climate is normally very cold. (-10°C average warmest month, coldest month can be however cold you want it to be). But, once every few years, the planet is closer to its stars binary companion* / the weather pattern changes / a nearby gas giant causes a big tidal effect to this area of the planet, and you have one hot summer (say 20-30°C average warmest month). The permafrost melts down to a depth of several metres. That's when your trees grow and your forest comes to life. Birds migrate from warmer regions (which experience deadly heat) to prey on thriving insects that breed in the meltwater left behind by the dense snowpack, flowers and plants bloom, spread seeds, multiply, etc.

The rest of the time, most organisms hibernate, and the forest is dead-quiet, frozen in time by a multi-year winter.

Notes

1. This can be easy to setup if you have a binary star system with eiliptical orbits. Even just an extra 10% sunlight means a 25°C temperature increase for an earthlike planet, and it only needs to be for a couple months.

2. I chose a hot summer rather than one near the minimum, as this allows for taller trees. In places which just barely meet the minimum summer length for trees (like eastern Siberia), you only get small stunted pine trees, not the big ones shown in the picture. The permafrost stops the roots from getting down very deep, is the problem.

3. As a side effect, Animals and plants living in this climate would be either longer-lived to survive several multi-year winters, or last for just that summer period (like the insects). E.g. if your multi-year winter is 8 years long, you'd have nothing with a lifespan between 3 months and 8 years. The migratory birds likely also live for 16-years plus: On Earth migration behaviour is mostly instinctive, not learned.

Answer 6

It's Alien

You say it's an Alien ecosystem, so you can make whatever you like. So it's possible they look quite like trees but their internal biology is nothing like them.

There's an entire underground ecosystem - lots of worm like creatures, bacteria, etc. maybe even a few burrowing rodent like creatures. Could be further diversified with extensive cave systems. Either geothermal heating softens up the "soil" for it to be penetrable, or whatever it's made of has a much lower freezing point than what we call "soil".

The tree-like plants can generate their own heat, so they can slowly thaw and push their way through the top layer and poke out into the fresh air, where they have access to that lovely juicy rainwater (snow, really, but their own heat generation let them melt it into water). The branch and needle configuration means not just the top layers get this snow and water, but it drips through, and therefore water gets to most of the tree.

Just a possible suggestion, but my point is you don't have to - or perhaps even shouldn't - follow the Earth model of a tree on an alien world.

As to how they reproduce? I'll leave that as an exercise to the reader :p

Answer 7

I feel like everyone is overlooking the elephant in the room: life as we know it requires liquid water. If it's never warmer than -10°C then there will be no life, period.

Answer 8

Seeding is the main problem. Seeding in ice stretches belief to my breaking point. Life itself may be possible with chemistry to depress the local melting point of water (anti-freeze, and energy from captured sunlight via photosynthesis).

They are alien, so maybe they don't seed. There are some alliums here on Earth which produce not seeds, but bulbils (small bulbs). Stretching this, maybe these alien trees are almost mammalian in their reproductive methods. The ovary of their flowers is produced underground (at a distance from the parent), and nurtures a seed becoming a young plant in a "womb" or "pouch" (marsupials) until it has a viable root and branch system of its own.

Maybe they don't need flowers either. They push out underground and reproduce clones at maximum range if thats all they can do. (Here on Earth, Quaking Aspen colonies). Sexual reproduction happens when roots from genetically distinct individuals find each other.

Alternatively the planet does have summers, but short cool ones at long intervals. A planet in a rather elliptical orbit, maybe. Life there has evolved not to shut down completely in winter, but to make the best of it, with tissues laced with anti-freeze chemicals and leaves which move to "shrug off" snow rather than relying on it falling off· But reproduction takes place during the short warmer season.

Answer 9

Timberline on mountains and the arctic requires 60 days a year where the temperature gets above 10 C. Below that they cannot photosynthesize enough to "pay" for the energy to grow a needle.

So, no, with Earth biochemistry this is a non-starter.

You need a way to keep viable chemistry at low temperatures.