Uprooting A Tree

[Steve Long]

During a cable-free long weekend thanks to late Thursday's ice storm, I had a lot of time to read, and while reading came up with a question I thought the fine folx of Discussion might like to consider:

 

How much STR does it take to uproot a tree? (Presumably said tree is then used as a club, or for some other helpful purpose.)

 

Since not all trees are the same, for purposes of this discussion I propose the following categories of trees based on size:

 

Small (e.g,, most saplings)

Medium

Large (e.g., centuries-old oak)

Very Large (e.g., redwood, sequoia)

 

Here are some pertinent facts and figures from various HERO System supplements:

 

STR required to lift a redwood:  72

STR required to lift a sequoia:  78

Basic stats for trees per 6E2 171:  4-5 PD, 3-4 ED, 5-11 BODY (though as usual, fully destroying a tree as opposed to just breaking it in two would require a good bit more than 11 BODY damage)

 

Since I don't want to waste time doing a whole lot of research on tree weight, root profiles, soil composition, etc. for a trivial gaming question, I suggest the following rules off the top of my head:  uprooting a tree requires STR equal to the STR needed to lift the tree, +5. In the absence of specific information about the weight of a given tree, the GM can assume that a lifting a tree requires Tree's BODY x 5 in STR (or can use some other formula he prefers). Uprooting a tree is a Full Phase Action (essentially it's a "Grab and Uproot").

 

Using the redwood and sequoia info above, I'd assign the various Tree Size categories ranges of STR to life, as follows:

 

Small:  25-29

Medium:  30-49

Large:  50-69

Very Large:  70+

 

What do y'all think?

[Scott Baker]

Given the parameters, I think this seems entirely reasonable.

[Old Man]

When it comes to uprooting trees, I tend to think less in terms of STR and more in terms of black powder or dynamite. Is that wrong?

[Steve Long]

No, I don't think so. I once spent a summer uprooting stumps with axe, shovel, and pick; dynamite would have been a lot easier (and more fun ).

[Christougher]

The only thing I'd suggest is Clinging, trees seem to be a pretty good case for.   The back and forth fight to break the Clinging with opposed STR rolls seems more entertaining too. 

 

Chris.

[Steve Long]

Not a bad idea at all, Chris -- thanx for the suggestion!

[TheRealDeal]

Perhaps assume the tree was Entangled in the Ground. This lets you play around with a lesser STR perhaps finally succeeding at ripping it out after several attempts (or taking an ax to the roots to speed up the process), and it would keep track of how much uprooting damage you have done thus far. The DEF of the Entangle would represent how hard the ground was, how deep the roots were, or whatever.

[Chris Goodwin]

According to this page, the biggest sequoia tree is known as General Sherman and weighs 1.2 million kilograms, 1200 tons.  Apparently some redwoods can reach 4000 tons as well.  For General Sherman that puts it at about 78 STR to lift, 23 BODY.  The 4000 tonners would take 81-82 STR, and have 25 BODY.  I might easily make Roots a Hit Location for 2x BODY ( ) which gives us pretty close to the numbers you came up with.  

[Christopher]

The only thing I'd suggest is Clinging, trees seem to be a pretty good case for.   The back and forth fight to break the Clinging with opposed STR rolls seems more entertaining too. 

 

Chris.

 

Perhaps assume the tree was Entangled in the Ground. This lets you play around with a lesser STR perhaps finally succeeding at ripping it out after several attempts (or taking an ax to the roots to speed up the process), and it would keep track of how much uprooting damage you have done thus far. The DEF of the Entangle would represent how hard the ground was, how deep the roots were, or whatever.

My thoughts went into both directions too.

Roll STR to uproot. Roll STR (or take a fixed Def) for the tree. Compare. If the uprooter wins, mark of by how much. Results add. Winning by enough uproots the tree.

 

Entangle offers the gamemechanic for what I though. In a lot ways Entangle is a "self sustaining, ranged grab". You can even break both with STR.

[lemming]

I was thinking clinging as well, though I think the idea of an entangle may be better since you're breaking the hold it has on the earth (or the roots).

 

So any STR beyond needed to lift the mass of the tree would go toward breaking thru the entangle.

 

Better stronger root system, more DEF.   Harder packed earth, more DEF.

 

And you wouldn't nessarily need full lifting strength either.  (A flier going further up the tree would get more leverage on the root system, assuming you don't break the trunk)

[Christopher]

I was thinking clinging as well, though I think the idea of an entangle may be better since you're breaking the hold it has on the earth (or the roots).

 

So any STR beyond needed to lift the mass of the tree would go toward breaking thru the entangle.

 

Better stronger root system, more DEF.   Harder packed earth, more DEF.

 

And you wouldn't nessarily need full lifting strength either.  (A flier going further up the tree would get more leverage on the root system, assuming you don't break the trunk)

The bigger the Tree, the bigger and more robust the root network. So basing the entangle strenght directly on Body/PD/mass?

In forrests root networks also tend to intertwine.

[Xavier Onassiss]

Another possibility: if you lift the tree out of the ground "roots and all" then you're just adding a number of hexes of soil/dirt/etc. to the mass of the tree you're lifting. A lot of it will fall off after the first hit (or two), but you get the idea.

 

Alternately, if you're breaking off all the roots, just give the root system as a whole the same DEF & BODY as the tree it's attached to for simplicity. (Roots are tough!) So that's another possible route, pardon the pun.

 

I don't have my books handy, or I'd finish both of these up and come up with some hard numbers. I'll just leave the rest for anyone who's interested....

[Sean Waters]

A tree with a 31 foot thick trunk would have a slice surface area of about 70 square metres.  Assuming you have to break off a metre thick bit, that is 70 cubic metres of wood to damage.  Wood has a density that varies quite a bit but let us assume that this wood has a density of between .5 and .6 metric tons per cubic metres.  That weighs 35 to 42 metric tons.  Although wood is living material we can probably treat it as unliving as it is largely homogeneous.  Treat that as a wall of wood weighing that amount and 6.2.172 gives us 16 Body to break it.  Wood has a PD of 4, probably.  So 20 Body in a single blow to break the trunk.  Twiddle as you will.

 

According to this page:  http://www.nps.gov/history/history/online_books/cook/sec5.htm

 

General Sherman has a volume, excluding limbs, of 49000 and something cubic feet, or about 1400 cubic metres, giving a minimum weight of 700 to 840 tons: adding in limbs and such, you are going to hit 900 to 1000 tons easily enough, I would guess.  That would require a strength of 80 to just lift.

 

I would suggest that the root system generally more than doubles the weight: think of a sapling you can carry around, but once it is bedded in you have no chance of lifting it out of the ground.  The root system, which can be nearly as big, if not necessarily as massive, as the tree itself is not just the weight of the roots, but also of the rock and soil it is clinging onto.  That will certainly weigh more than the tree above ground.

 

I would suggest you would probably need to be able to lift at least four times the weight of the tree (i.e. STR + 10) to pull it out of the ground, possibly more (maybe STR +15 for 8x).  that would put a minimum uproot strength for a really big tree at 90+ STR.

 

You will definitely need superhero physics to manage that, in any event, but leaving that aside, I would say really big trees would need 90 to 100 STR to shift, which is a reasonable approximation of accuracy between pulling it out of the ground and snapping the trunk.