How does forest growth work?

[EscapedGoat]

I have generally been chopping the lot down, because that suits my expansion strategies. I am interested to see if someone has figured out the rules of regrowth. Like:

-Apparently, forest only grow on unimproved tiles, but can grow on roaded tiles? Do forests grow on worked tiles that are not improved? or do you have to leave the tile completely alone?

-How often do they grow(not very often in my experience)

-When growth happens inside your territory, you get a message about it I think. What about outside your borders? do they grow there too?

-Do forests grow to places there was never a forest in the first place?(I am allmost 100% sure I have seen this happen though)

-Is there a higher chance of growth in a place where there used to be a forest before?(I once had a forest regrow allmost immediately after I chopped it. I just said 'thank you' and chopped it again.)

-Is there a higher chance for a forest to grow in a tile surrounded by other forests?

[Mathemagician]

i can say that much:

- i think i have seen forests grow only within cultural borders so far i think. or at least i only got messages there.

- often there will be situations where it looks like trees are growing or are cut, for example when you build a road on a forested tile, a few trees will disappear. or when you enter a hut and the hut is removed, the graphics will show more trees afterwards.

- i once got a message that a jungle has grown. its probably rarer as you'll not as often have cities near jungle as near forest.

- i think it would be rather dumb if forests grew on improved tiles, effectively killing the improvement there. i dont think this works this way.

[Handel]

I've never seen forests grow on improvements tiles, even only with a road there.
And later in the game I see no forest growing, so I guess if you work a tile, it will not grow a forest, even if there are no improvements at all.

[-Ab-]

-Is there a higher chance for a forest to grow in a tile surrounded by other forests?

yes deffinately
they will grow quite often if the area of trees in the local vacinity is quite large but as far as hard facts and figures go i dunno
a block of 9 trees eg 3x3 its fairly likely to grow a new tree somewhere but i have never seen a single square expand

[The keeper]

I believe forests grow faster in the early game.

Makes sence since a turn in the early game is longer (years) than a turn in the late game.

[SirOsis]

I've also had Jungles grow.

[Metaliturtle]

Has anybody done a test map with a 3 x 3 grid of trees and harvest the center one to time turns until regrowth?

Ex:
TTT
T T
TTT

T=Trees

Also could check # of Game years

Or, for those of you who think j00 R teh U|3eR 1337! maybe you could "hax0r" a bit and find the tree regrowth algorithm?