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[Bumber]

I don't want to get dragged back into this, but there are a few points I feel need addressing:

What your 7 year forest map looks like compared to someone else's 4 year savannah map is completely irrelevant to this discussion. The issue at hand is that after a few years a map of a tree-sparse biome will have become very tree-dense. Vattic has already provided evidence that this phenomena occurs; I have not seen any evidence suggesting the contrary.

Since the trees that are placed originally themselves bear no resemblence to what the trees ought to look like having had hundreds of years to grow, it is pretty much irrelavant that the total number of trees that we end up with on a savanna is greater than we started off with, since the trees are also a lot bigger than they started as well.  Fact is that the original trees are not grown using the model that is used after embark, they are placed using a relatively crude script. 

Since the total number of trees that existed on embark is *not* the number of trees that ought to be there given the mechanics actually in play in the game, it is far harder to prove there is a problem that simply pointing a finger at the number of trees we end up with at any given biome and pointing out that there were more that we started out with.  In order to prove there is a problem we either have to prove there is actually no limit at all on tree growth or that the limit is exactly the same on all biomes.

It is absolutely trivial to prove that there is a problem because that is not what a savanna is. Real life savannas have had thousands of years to grow and they aren't densely wooded. Time is irrelevant. This is more than sufficient proof for a suggestion. This thread is not a bug report. You can't dismiss it with the "mechanics at play".

For what it's worth, Toady has stated that trees are supposed to grow/replenish slower in certain biomes. To my knowledge, he has not made any guarantees about end states being properly modeled. He's going to track soil quality eventually^TM.

Why not? The devs are human and capable of making mistakes, and Dwarf Fortress isn't even complete yet. Who are you to say that this isn't something Toady either overlooked or knows about and intends to fix later? You have zero proof of the dev's intent.

Neither do you.  Nor do I need any proof, since the conclusion follows from reasonable premises; it is reasonable to assume that the devs do not want uncontrolled tree growth on all biomes, hence if they are developing a model for tree growth they will have implemented some limitations on said tree growth.  You can of course prove me wrong by actually demonstrating that this is not the case, but the devs are stupid is not a reasonable premise to draw conclusions from.

Saplings (and other trees) were growing way too fast, and that is fixed now.

He messed it up once. There's a real chance even that is still not properly fixed.

There are very clearly observed clusters on the savanna map, areas where trees simply refuse to grow, the clusters on the forested map however are a lot smaller and more disputable.

I pointed out it was very likely a biome border in my previous post. Only Vattic can tell us for sure.

[cochramd]

My experimental forest embark started in year 5, looking like this:

Spoiler (click to show/hide)

This what it looked by summer of year 8, after doing exactly what Vattic did:

Spoiler (click to show/hide)

Much less growth than expected, so I waited another year and took a screencap of the autumn:

Spoiler (click to show/hide)

The game then promptly crashed, but I think I have all the data I need. I have concluded that whatever Toady has implemented to prevent treesplosion works for tree-dense biomes but not for tree-sparse biomes.

[PatrikLundell]

I've concluded that my biome is a Tropical Shubland. After 18 years I can't detect any difference from the 14 year one (but it's an Eyball Mk I + Degraded Memory comparison). That seems to support the notion that there is a brake somewhere, but, as Cochramd said, it's applied too late for sparse biomes.

[cochramd]

It's not even a brake, really, just an equilibrium being reached. The majority of my embarks have been tree-dense, and I've seen plenty of post-clearcutting treesplosions. Toady has said that it is his intention that saplings die when they try to grow in the shade, and these treespolsions are strong evidence that shade from other trees is now the only thing that keeps tree growth in check. Once Toady implements soil moisture, soil quality and erosion, tree-sparse biomes will stay tree-sparse, and post-clearcutting treesplosions may stop occurring as well.

[PatrikLundell]

The problem with soil moisture, etc. is that it's likely to be quite far in the future, and I've gotten the impression Toady isn't too keen on spending effort on temporary measures that are to be torn up again. However, I think either a priority shift or a temporary measure is needed here...

[GoblinCookie]

Thumbs up for expressing what both of us think with a quick analogy, cochramd!

GoblinCookie: Okay. Fine. I will reduce my statement to one (not as easily definable) point:

There are too many trees.

Savannas should not have that many trees.

And you know what? I'm going to go ask Toady. That's what somebody did on the religion thread, and it seemed to work somewhat.

Here is your answer. 

I'm not really sure how it'll end up.  We need to deal with the youngest trees differently, since there's that pop when they get a full trunk and that happens too soon in the process.  They can probably afford to grow slowly overall, so that you feel you are losing your forest by chopping it down, but I don't really have a feel for how it ends up after 20 years currently.  Tree density should eventually depend on the rainfall, if that's broken -- there's a water use field that gets used during initial placement, but I don't recall how it acts or if it even exists after play begins.  Nothing has changed for this time that I remember.

I believe that presently tree-growth is regulated by randomly generated clusters, some of them prohibit the placing of trees and others permit the placing of trees.  The more forested the biome is, the more of the clusters are wooded as opposed to non-wooded, the reverse being the case in the less forested biome.  Basically the game is not divided up really into wooded biomes and non-wooded biomes as a whole but instead into a crude binary of forest clusters vs plains clusters. 

The initial trees are initially placed within the clusters according to the biome, but there is little or no difference between biomes as far as the initial end-state is concerned within a wooded cluster, in any case the two disagree.  The reason for this is not a mistake of the devs but rather the undeveloped nature of the modelling of moisture/nutrients in the game; it does not make sense for them to develop elaborate, in-depth place-holder mechanics simply in order to replace them later. 

[Dozebôm Lolumzalìs]

And that is what I have been saying all along! 

Thumbs up for expressing what both of us think with a quick analogy, cochramd!

GoblinCookie: Okay. Fine. I will reduce my statement to one (not as easily definable) point:

There are too many trees.

Savannas should not have that many trees.

And you know what? I'm going to go ask Toady. That's what somebody did on the religion thread, and it seemed to work somewhat.

Here is your answer. 

I'm not really sure how it'll end up.  We need to deal with the youngest trees differently, since there's that pop when they get a full trunk and that happens too soon in the process.  They can probably afford to grow slowly overall, so that you feel you are losing your forest by chopping it down, but I don't really have a feel for how it ends up after 20 years currently.  Tree density should eventually depend on the rainfall, if that's broken -- there's a water use field that gets used during initial placement, but I don't recall how it acts or if it even exists after play begins.  Nothing has changed for this time that I remember.

I believe that presently tree-growth is regulated by randomly generated clusters, some of them prohibit the placing of trees and others permit the placing of trees.  The more forested the biome is, the more of the clusters are wooded as opposed to non-wooded, the reverse being the case in the less forested biome.  Basically the game is not divided up really into wooded biomes and non-wooded biomes as a whole but instead into a crude binary of forest clusters vs plains clusters. 

The initial trees are initially placed within the clusters according to the biome, but there is little or no difference between biomes as far as the initial end-state is concerned within a wooded cluster, in any case the two disagree.  The reason for this is not a mistake of the devs but rather the undeveloped nature of the modelling of moisture/nutrients in the game; it does not make sense for them to develop elaborate, in-depth place-holder mechanics simply in order to replace them later. 

[Vattic]

I didn't think to check vegetation before embark because of a myopic focus on trees. Figured the bright display was fairly representational of arid climates when in bloom, but it would be interesting to know if vegetation does the same as trees.

Just retire and check a tile from that same biome.

But first check the z-level above. I'm curious if it's only shade from leaves that's stopping forest embarks from being even worse. Could just be that "two saplings growing at the same time" thing either way.

Other vegetation is "Moderate" at embark.

Your savanna map shows the cluster effect far more strongly than my own screenshot did, although it is only 3 years rather than 7 years apparantly.  This confirms what I have been saying, the map is randomly divided up into forests/nonforested zones, the less forested the map is supposed to be the larger the nonforested zones are.  While the non-forested zones are small on my map, the non-forested zones are huge on yours, the whole eastern section of your map is such a zone. 

As others have noted the eastern part of the map borders a rocky wasteland.