Some of the main differences between the heart and sapwood is what PatB was getting at. The sapwood/xylem usually has more moisture in it than heartwood.mthe heartwood is kind of retired, it did its job and has been inaugurated in the heartwood club where it will stay. The heartwood is rich with sugars, oils and various minerals.
The sapwood often is not rot resistant and usually softer. I'm guessing that the rot resistance has to do with the heartwood being settled into its permanent state and the oils and such that are in it help prevent decay. Softwoods are non porous and hardwoods porous. Hackberry is ring porous, but it usually is hard to see much color change. I've wondered why Hackberry is good with a sapwood back and have not heard of anyone making a heartwood bow out of it. Which leads me to wonder if a heartwood hackberry bow would last longer? Hackberry can have really thick early wood rings sometimes and other times thin, I've noticed. I have processed two Hackberry trees recently and they are such opposites and they grew fifteen feet apart from each other. That kind of stuff interests me.
A fellow arborist was telling me the other day a tree that is completely rotten in the middle is by far safer to climb than a tree that has good heartwood and rotten sapwood. I've noticed this too while climbing/removing dead trees. It's been shown though the reason for this is not superior sapwood strength, but the cylinder shape that gives the tree strength. Like an empty coke can, very thin walls but it's the cylinder shape that gives its strength.
Often sapwood is more bendy, but it also has more moisture and is 'green'. I think about things like this a lot too upstate and when I'm working I am always testing and experimenting with trees. By the way Upsate I really enjoy your work, something for me to aspire to, take care.
