Could a climate JUST under 10 C / 50 F year round grow trees?

[Brittany Spice]

Yeah it's possible but depending of latitude, soil and moisture conditions. A climate like this probably be a woody toundra. To my work, difference can be found be found here:
-Boreal/ subalpine forest:at least 2 months above 10°C and 3°C of annual temperature (take 0 for negative values).
-Tundra: at least one month above 5°C and 1.5°C of annual temperature (take 0 for negative values).

[deneb78]

Originally Posted by Mhc1985

Yes, in Tierra del Fuego there are some forests in areas where the warmest month must average around only 7ºC!!

That is about the same as the Kerguelen Islands and no trees grow there even in sheltered locations

[popartist]

Trees survive in Iceland, where this is pretty much the climate. The only reasons why there aren't a lot there are because 1) volcanic activity made a lot of terrain inhospitable to any vegetation and 2) there was a lot of deforestation in the early days of settlement there.

Forestry in a treeless land | Iceland Forest Service | Skógrækt ríkisins

[Mhc1985]

Originally Posted by deneb78

That is about the same as the Kerguelen Islands and no trees grow there even in sheltered locations

Yeah, I'm not sure about what the special conditions in Tierra del Fuego are in order to allow the growth of forests at such low temperatures. It's a damn windy and gloomy island where forests are widespread throughout the southern half of the territory, where january averages fail to surpass 10ºC, and get lower towards the east. Forests still grow up at an altitude of 500/600 m.a.s.l. in some sites.

To make it worse, between two areas of Tierra del Fuego and Kerguelen where the summer temps are about the same, the one of Tierra del Fuego is overall colder (and higher, of course).