Aluminum nails in live trees cause significant damage?

[Dean Faklis]

Recently in my email inbox, there has been some discussion on hanging posted signs on live trees with aluminum nails.  I've read that using aluminum nails does negligible damage to the tree. 

The computer screen background on this webpage is a nice array of taphole maple lumber.  The taphole causes an injury and a stain column forms above and below the hole.  The length of the stain column appears to be proportional to the size of the taphole.  Smaller holes appear to lead to a shorter stain column. 

Consider that a 5/16" diameter drill bit might cause 25 cu. in. of stained wood when hole depth is 2".  That's a hole volume of about 0.153 cu. in. giving rise to 25 cu. in. of stained wood.

An 11 ga aluminum nail has a diameter of 0.12".  Let's say that we need to pound the nail in 1" to effectively hang a sign.  That's a hole volume of about 0.011 cu. in.(per nail!), which is about 14 times smaller than the taphole considered above.  If a 5/16" diameter hole in 2" deep gives 25 cu in of stained material, then it might be reasonable to assume that a single 11 ga aluminum nail wound would give 25/14 or about 2 cu in of stained material.  If you need 4 nails to hang a sign, that's 8 cu. in. of stained wood.  Use 8 nails and the damaged area grows to 16 cu. in., which is approaching the damage of a taphole.

Now, there are a lot of assumptions here!  But it seems that using nails of any variety might cause "significant" damage to sawtimber.  Please poke holes (pun intended!) in my argument and/or point to research.