Making Sense of Forest Terrain

Thinking about this further: If tree trunks are always considered to be at grid intersections, then "tree" squares are the 4 or 12 squares in a 5 ft or 10 ft radius from the trunk. "Massive" tree squares are then the 4 squares completely blocked by a massive tree trunk growing at the intersection.

I don't think I like this, but it isn't ridiculous the way my original interpretation was.

Have the bard sing a song.

[video=youtube;RGT4V6JmINA]https://www.youtube.com/watch?v=RGT4V6JmINA[/video]

A forest is as dense or sparse as you wish, just never with the trees in nice neat lines, for, that is a tree farm. But then you could just stick the party members in the eye with a twigs. Or smack them with branches when the less dexterous walk through.

Edgar Ironpelt said:

Either the "Forest Terrain" rules in the 3.5 SRD don't make any sense, or I'm grossly misinterpreting them.

There's an old thread about how the percentages for "trees, massive trees, etc." are suppose to be guidelines for GM mapping rather than 'Roll for each 5 ft square to see what terrain it has.' That would make sense - except that the percentages, as near as I can tell, are off by an order of magnitude.

Googling gives me figures of 100 trees/acre or less as sparse forest, and 200 trees/acre or more as "overgrown" in the real world. But using the SRD figures, 50% trees per 5 ft. square - supposedly "sparse" works out to ~860 trees per acre, with dense forest being twice that.

As a quick fix, I'm thinking of taking the SRD percentages and applying them to "per 15x15 grid of 9 squares" rather than "per square." That gives ~100 trees/acre in sparse forest, ~150 trees/acre in medium forest, and ~200 trees/acre in dense forest.

What do other people do?

Click to expand...

I think that's it's time to step back and forget about rules or the exact number of trees, and just describe the terrain as whatever you want it to be and not worry about it past that. After all, it's just a game of playing pretend.

Edgar Ironpelt said:

OK, that's one way to look at it. Except... this means that standing under a tree allows you to use the tree as cover, or to climb it, even if you are standing 10 or 15 feet away from the trunk, and even if the branches are high enough that you don't have to duck. Also, how then do you interpret massive trees in medium or dense forest?

If a "massive tree" square is occupied by the trunk of a tree thick enough to prevent entry, then "10% massive trees" in medium forest comes to 174 trees per acre and "20% massive trees" in dense forest comes to 348 trees/acre. Which is still an awfully lot, especially when we're talking about big trees with trunks thick enough to completely block a square. Alternatively, a massive tree has to completely block some of the squares under it with something other than the tree's trunk. How does that work?

Click to expand...

Have you ever been in a forest? What type of forest?

Look at the image from the video @Draegn posted. Those are old growth trees that might not have any branches closer than 15 feet to the ground with a trunk that may be two feet in diameter.

Then you have "new" forests like you will find in much of the US, where the tree limbs touch the ground and moving into them is at least difficult terrain and provides visible cover from outside the tree.

Both of those types of forest will have roughly the same number of tree per area. But both play very differently in an RPG. The numbers work, if you have the same understanding as those who wrote them. If you have a different understanding, or make different assumptions, then change them.

Oh, and don't put the trees on every grid intersection or every grid center. Spread them around or your forest will look fake.

LordEntrails said:

Have you ever been in a forest? What type of forest?

Look at the image from the video @Draegn posted. Those are old growth trees that might not have any branches closer than 15 feet to the ground with a trunk that may be two feet in diameter.

Then you have "new" forests like you will find in much of the US, where the tree limbs touch the ground and moving into them is at least difficult terrain and provides visible cover from outside the tree.

Both of those types of forest will have roughly the same number of tree per area. But both play very differently in an RPG. The numbers work, if you have the same understanding as those who wrote them. If you have a different understanding, or make different assumptions, then change them.

Oh, and don't put the trees on every grid intersection or every grid center. Spread them around or your forest will look fake.

Click to expand...

Yes, I've been in forests before, both the kind where the first limbs of the trees are 15 feet up, and the kind where the limbs are so low as to produce a "heavy underbrush" effect or worse. And a few kinds in-between.

My point is that, by the SRD:
A creature standing in the same square as a tree gains a +2 bonus to Armor Class and a +1 bonus on Reflex saves (these bonuses don’t stack with cover bonuses from other sources). The presence of a tree doesn’t otherwise affect a creature’s fighting space, because it’s assumed that the creature is using the tree to its advantage when it can.

and I initially presumed that this bonus is due to being in the same square as the tree's trunk. But if it's not due to being in the same square as the tree's trunk (because that gives way too many trees and therefore must be a wrong understanding), then what is this bonus due to? If a tree's limbs and branches are low enough to provide cover, then I can't imagine them not also hindering movement. And if the tree's limbs are high enough to allow free movement under the tree's canopy, then how can they provide those cover bonuses?

Similarly with "massive trees" If an impassable "massive tree" square is not the trunk of a tree with a 2+ ft diameter, then just what is it? Because making it the trunk of a tree makes the numbers come out wrong. Therefore (by your premise) the people who wrote the rule must have had a different understanding. But what was that understanding?

I occasionally use a random table to determine what species of tree is in an area, but I've never rolled to determine how many trees... just make it up.

Edgar Ironpelt said:

Googling gives me figures of 100 trees/acre or less as sparse forest, and 200 trees/acre or more as "overgrown" in the real world.

Click to expand...

I don't play 3.5E, but I think this is where you went wrong. My search for average forest trees/acre yields a much wider variation of figures, based on factors like individual species represented, average tree diameter, and the age of the stand. Here's a quote from a pdf on "Forest Thinning" put out by http://4hforestryinvitational.org:


The 100-200 trees per acre figure you quote appears to come from this website: http://www.sbcounty.gov/calmast/sbc/html/healthy_forest.asp. Note this article is about preventing wildfires in Southern California and that 100-200 trees per acre is considered overstocked, whereas 40-60 trees per acre is considered healthy when seen through the lens of fire-prevention that the article presents. If you have another source for these figures I'd be interested.

My point here is that figures for average trees/acre in a forest vary depending on the particulars, and in most cases they are expressing an ideal based on whatever forest management goals the author has in mind, whether it's maximizing productivity of the land for harvesting lumber, preventing fires, or some other goal. Assuming the forests in your fantasy world may or may not be under similar management regimens, the figures available may or may not be relevant. When all this is taken together, I think the 871 to 1,742 trees/acre yielded by following the SRD rules are within the realm of plausibility. I also think that what qualifies as a forest in the real world hasn't been well defined.

Edgar Ironpelt said:

What do other people do?

Click to expand...

Again, I don't play 3.5E, but when I design outdoor encounters for my 5E games, I use a homebrew system that randomizes terrain features based on the prevailing terrain. So, for example, if an encounter takes place in a forest, I generate terrain for each quadrant of the map from a table that includes the following results: featureless, dense woods, light woods, dense brush, rough ground, slope, hill, marsh, stream, or pond. I mention this because what I think the 3.5 SRD system is lacking is an acknowledgement that what we call a forest in the real world is actually made up of many terrain elements that merge in complex and varying ways. I also think that keeping that in mind may help with the dissatisfaction you seem to be expressing with the 3.5E system. A forest isn't just made up of wooded areas. There are meadows, floodplains, rockfalls, etc., where very few trees grow but are nevertheless considered part of the forest.

ccs said:

Hey, if you want to spend your prep time counting fictional trees within a hypothetical acre, knock yourself out....

Click to expand...

You know, scoffing at others because they want to do things differently than you... is not a good look.

It is fine to not want, or feel a need for such details. And to express that, and maybe even ask *why* someone would like those details.

But there's no call for the snark, y'know.

Imagine two gamers: One lives in the US Midwest - farm country, and has never been in a forest. The other lives in the Pacific Northwest, and has effectively lived most of her life in a rainforest. They meet at a game in college in Texas, and the GM (who grew up in New Jersey) says, "the forest is sparse." Do you figure these three people have the same image in their heads of what that means?

Relative and qualitative measures and language only make sense if you start with a similar understanding. The books giving you objective measures is nice when you don't all come at the game from the same place.

Edgar Ironpelt said:

My point is that, by the SRD:
A creature standing in the same square as a tree gains a +2 bonus to Armor Class and a +1 bonus on Reflex saves (these bonuses don’t stack with cover bonuses from other sources). The presence of a tree doesn’t otherwise affect a creature’s fighting space, because it’s assumed that the creature is using the tree to its advantage when it can.

and I initially presumed that this bonus is due to being in the same square as the tree's trunk. But if it's not due to being in the same square as the tree's trunk (because that gives way too many trees and therefore must be a wrong understanding), then what is this bonus due to? If a tree's limbs and branches are low enough to provide cover, then I can't imagine them not also hindering movement. And if the tree's limbs are high enough to allow free movement under the tree's canopy, then how can they provide those cover bonuses?

Similarly with "massive trees" If an impassable "massive tree" square is not the trunk of a tree with a 2+ ft diameter, then just what is it? Because making it the trunk of a tree makes the numbers come out wrong. Therefore (by your premise) the people who wrote the rule must have had a different understanding. But what was that understanding?

Click to expand...

Sounds like you have a reasonable expectation, that the bonuses are due to using the tree trunks protectively and not the concealment due to branches (because I agree, they would impede movement). As for the numbers... I again don't see that as the number of tree trunks, but I guess it could, and then the numbers wouldn't make sense.

Don't know what to tell you.

Hriston said:

I don't play 3.5E, but I think this is where you went wrong. My search for average forest trees/acre yields a much wider variation of figures, based on factors like individual species represented, average tree diameter, and the age of the stand. Here's a quote from a pdf on "Forest Thinning" put out by http://4hforestryinvitational.org:

An adequately stocked stand will have fast-growing trees of good form. For example, consider an even-aged hardwood stand. There may be well over 10,000 seedlings per acre in the first 5 years. This number decreases to about 1,000 as the stand matures to a point when the trees average 5-11 inches DBH (pole-sized). Most of the young trees naturally die as other trees out-compete them for sunlight. When trees average more than 11 inches DBH (saw-timber size), the number of trees declines to 500 trees per acre, and eventually to 150 trees per acre in very mature woodlands.​

The 100-200 trees per acre figure you quote appears to come from this website: http://www.sbcounty.gov/calmast/sbc/html/healthy_forest.asp. Note this article is about preventing wildfires in Southern California and that 100-200 trees per acre is considered overstocked, whereas 40-60 trees per acre is considered healthy when seen through the lens of fire-prevention that the article presents. If you have another source for these figures I'd be interested.

Click to expand...

"It's a fair cop, guv." I didn't rely entirely on the So. California numbers, but I did put disproportionate weight on them. Mostly because the other figures I found ran heavily to tree densities resulting from deliberate (and therefore unnaturally intense) reforestation efforts. So I discounted figures like the ones in your quote from "Forest Thinning" as being viewed through the lens of maximizing timber production.

Also, I was making the unstated assumption that typical forests in D&D-land would run more toward being older - not necessarily "old growth" but at least older second-growth with the oldest trees having ages of over a century. The kind of forest where the trees might average 11 inches or more in diameter and would be thinned out to (and past) the 500 to 150 trees/acre figures in the "Forest Thinning" article you quote.