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This is the classic winter picture of a boreal forest, or taiga. This habitat exists only on subpolar latitudes, where the climate is too extreme for broad-leaved angiosperms to take root, thus making the taiga an exclusive conifers-only club.

In an alternate Earth, there is a clear ecological distinction between the two types of trees. Broad-leaved angiosperms lord over the lowlands whereas conifers can be found only on the cooler, drier and rockier highlands. So where does that leave the taiga?

In this same alternate Earth, the boreal forest consists primarily not of conifers, but a kind of grass called bamboo.

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Now in order to survive in a latitude where the summers are short and the winters bitterly cold, these boreal bamboos may have to grow more slowly--like, instead of six weeks to reach the maximum height of 100 feet, it happens in six years. Is this change in adaptation enough for bamboo forests to thrive in subpolar latitudes, or should more changes in characteristics be required?

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  • $\begingroup$ Yes, that change is sufficient. $\endgroup$ – kingledion Mar 27 '17 at 1:30
  • $\begingroup$ Sufficient for the height piece but slow growth by itself is not enough to tolerate the cold. $\endgroup$ – Willk Mar 27 '17 at 1:35
  • $\begingroup$ @Will Is there anything else? $\endgroup$ – JohnWDailey Mar 27 '17 at 3:39
  • $\begingroup$ That sort of forest doesn't only exist at subpolar latitudes, but also at higher elevations in the mid-latitudes. (Indeed, except for the blue sky, it looks rather like where I was cross-country skiing today.) I think the limiting factor isn't just temperature, but moisture as well. (E.g. a lot of the US west isn't that cold, but broadleaf trees are found only near springs & streams.) So your cold-tolerant bamboo probably needs to conserve water as well... $\endgroup$ – jamesqf Mar 27 '17 at 4:07
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    $\begingroup$ Colder adapted bamboo only grow for part of the year, they still grow fast but they only grow during the summer, you see this in the american varieties. What kills temperate bamboo in the cold is frostburn. bamboo has shit for insulation so the leaves literally freeze and die during a cold snap. At high latitudes sun scalding will kill them almost as well, again because they have poor insulation they sun can bring the stem out of dormancy and then the night time cold kills it. So likely your bamboo will grow fast but die in the winter, so you get a fast growing dwarf bamboo forest. $\endgroup$ – John Mar 27 '17 at 5:45
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I have been pondering this concept more than is healthy. Why does bamboo not outcompete woody trees everywhere? Bamboo can give woody trees a lot of competition almost everywhere. Even in the cold, bamboo can outcompete a lot of other plants. I found this image of a cold hardy dwarf bamboo taking over an alpine meadow. From https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3287379/

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I suspect bamboo has not taken over the earth because it has such a hard time propagating by seed.

The below image gave me an idea about how to make the boreal bamboo forest work. enter image description here

From http://qscaping.com/20000020/Plant/19741/Hedge_Bamboo This bamboo is growing in Saskatoon, Saskatchewan. It is rated to zone 8. Saskatoon is zone 3b. It grows fast and grows tall in the summer and then if you leave it outside, it dies.

I propose the boreal bamboo forest be deciduous in its entirety. All above ground parts die and blow down in winter storms. The handwaving piece: a root which can weather the winter underground. As soon as the days start to get longer the forest erupts from the ground. Maybe the spring growth is just photosynthetic stems, and the leaves come out when it warms up more. Instead of growing slow, it grows crazy fast in the long days and by late summer the forest is there. In fall, it all falls. The stems would get brittle and break, so as not to pull up the root with leverage from the plant.

A normal bamboo forest is hard enough to walk through. The bamboo is so close together. This bamboo forest would be pretty much impossible to traverse at any time: the ground would be a thicket of fallen bamboo trunks piled and crossed over each other, with broken dry growth from previous years like punji sticks among them. Not a place for anything with long legs.

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You have several problems:

  1. Tropical trees often have only a single set of enzymes -- They work well in a fairly limited temperature range.

You can see this somewhat in eggplants. You get a cool night say 50 F and an eggplant will 'sulk' for 3 days. Certain reactions ran at the wrong relative rate, and the plant spends its energy doing housekeeping.

Treeline is roughly at the point there are less than 60 days a year that it gets above 10 C. Less than this the best you can hope for is Krumholtz. I did a canoe trip north of treeline. We harvested scrub birch -- pencil sized chunks -- for firewood to cook supper. That pencil sized chunk of deadwood had 50 growth rings in it.

  1. Plants have various mechanisms to cope with freezing. Most of them need lead time. Some plants do this by temperature -- x cold nights in a row trigger the start of dormancy. Some do this by day length. There are bamboos that grow in climates with seasons. Check to see how they have adapted.

There are two levels of adaptation. For plants that can take moderate frost (zone 5 -7 ) this is usually moveing excess water out of cells, concentrating the ions and disolved sugars inside the cell. This lowers the freezing point.

Colder temperature plants augment this by accumulating glycerols and alcohols in their tissues. Get enough junk in solution and water doesn't freeze so much as turn into a glassy solid with out crystals that slice up cell walls.

  1. Dehydration. The roots are frozen. No water transport. The top of the tree is out in the wind. One of the best reasons to have deciduous leaves is that you don't have to keep them alive over the winter. Lots of trees can take the cold, but can't take the dehydration of month after month of bright sun, and cold breezes.

  2. The taiga is a cold desert. Much of that country gets only about 10 inches of precipitation a year. The boreal areas aren't much better at 16-20 inches. You still have a lot of standing water there because it's cold enough that the evaporation rate is low. A plant that is used to having 60 inches or so of rain won't have a root system that spreads far enough.

  3. Very shallow soils. Much of that country has only a few inches of soil on top of granite. Lower areas are peat bogs. Water is largely unmoving, low in oxygen once more than a few inches below the surface, acidic pH of around 4.

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