What tree species gives the most BTUs per acre per year?

[downeast]

Bit of confusion here 
% moisture content is measured by comparing the DRY weight of a piece of wood, with it's current weight. And thats done by drying it in an oven untill ALL the water is driven out.
So say you had a piece of wood weighing 1lb, you oven dry it untill it's totally dry and it weighs 1/2 lb.
That means it had 1/2 lb of water, and 1/2 lb of wood, the ratio is 100%.
It is not exactly the same as we measure percentages in other stuff, but it's how moisture in wood is measured. Don't ask me why, but I suspect it's to make the maths easier as it's measured from DRY, not from some random wet measurement.
Re the Wood regaining moisture, yes it does, real world. I've tested green blocks of wood by microwaving them untill they got no lighter. 0% moisture. Then you leave it out on the bench for a week, and it re-gained some of the weight, about 12% eventually.
You can test this youself if you want. 
Ian

Sorry Ian et. al, We're back to Groucho's duck.
If you measure a body's % of moisture it is the %. Period. That's what we Call Scientific Method. Ain't no other valid measurement.    That is what a Closed System will measure. It's controlled, repeatable, accepted. Now, if you want to make another kind of measure, fine, like 200% moisture content !!!??!? . But it's not science or real.
It's kind of like the arguments over what a cord is. Rick, face, banana cord, volume, mass, air space, round logs, tighly packed splits, lamb chops, Dodge Ram pickup bed cord. Everyone knows. 

BTW Ian: why does NZ policy mandate plantation reforestation. Single species, in neat rows on the hills. It is strange to see this lack of diversity and 'order'  for a healthy regen.

[beenthere]

de  Care to elaborate more on what it is you are hinting at?

[WDH]

Now, truth telling time: have you done this with that block of wood in a closed system ? Real world, real time.

Yes.

[Ianab]

That is what a Closed System will measure. It's controlled, repeatable, accepted. Now, if you want to make another kind of measure, fine, like 200% moisture content !!!??!? . But it's not science or real.

The science is the same, it's just what are you comparing? It's just a ratio, expressed as a percentage.
It's the amount of water compared with the amount of DRY wood. The amount of dry wood is a fixed value, the weight of green wood is a variable. Imagine trying to do the maths on drying rates if you were working from percentages of the current moisture content, which is a moving number.

It may be more correct mathematically, but in a practical sense it's a nightmare.

BTW Ian: why does NZ policy mandate plantation reforestation. Single species, in neat rows on the hills. It is strange to see this lack of diversity and 'order'  for a healthy regen.

Simple economics. 99% of the timber production in NZ is introduced plantation forest. Pine, Douglas fir or Euclayptus grown on a 20-50 year rotation. It's planted and harvested as a crop, just like corn or beans, just a little longer between planting and harvesting.  None of your timber speces are endemic to NZ, and the native species are very slow growing with a complex succession process through several stages of forest growth. Might be 50-100 years before the desireable crop trees are even established, and maybe 300+ years for them to mature. A forest giant might be 800+ year old.

So you have 2 types of forest, commercial plantation, mostly pine, which is intensly managed and harverested. And native forest, which is only a fraction of the original pre-human amount and is mostly preserved in parks and reserve land. Either untouched or slowly regenerating.

There is some limited harvesting of native timber from private land, but it's strictly controlled and the annual timber supply is very small.

Ian

[SwampDonkey]

downeast, the methods for measuring wood MC is tried and true. Been done longer than you and me have been on this planet. There is also two kinds of water in wood, bound water and free water. Free water effects weight only and bound water affects, weight, specific gravity, volume and other physical properties of wood. The threshold where volume and physical properties of wood change is the fibre saturation point, which can't really be pinned to one exact MC%, but academically they use 30 % MC as a point of reference. Hard maple, beech, yellow birch and eastern spruce and fir are very close to that figure. You need to know these things when making paper because water doesn't make you money, only wood fibre. It's like trying to make bread and thinking the amount of water doesn't matter, there is a recipe. 

Wood moisture is measured that way because physical properties continuously change from green condition until every bit of moisture is removed (oven dried). Don't confuse air dried seasoned wood for oven dried. Seasoned wood varies by climate and reaches equilibrium with the surrounding air, they call it the Equilibrium Moisture Content. Why you suppose they set your flooring lumber in your living room for a week or two? To get the wood to equalize with the climate in that room.

If you can't grasp that then relative humidity is really going to jam those wheel cogs.

[downeast]

downeast, the methods for measuring wood MC is tried and true. Been done longer than you and me have been on this planet. There is also two kinds of water in wood, bound water and free water. Free water effects weight only and bound water affects, weight, specific gravity, volume and other physical properties of wood. The threshold where volume and physical properties of wood change is the fibre saturation point, which can't really be pinned to one exact MC%, but academically they use 30 % MC as a point of reference. Hard maple, beech, yellow birch and eastern spruce and fir are very close to that figure. You need to know these things when making paper because water doesn't make you money, only wood fibre. It's like trying to make bread and thinking the amount of water doesn't matter, there is a recipe. 

Wood moisture is measured that way because physical properties continuously change from green condition until every bit of moisture is removed (oven dried). Don't confuse air dried seasoned wood for oven dried. Seasoned wood varies by climate and reaches equilibrium with the surrounding air, they call it the Equilibrium Moisture Content. Why you suppose they set your flooring lumber in your living room for a week or two? To get the wood to equalize with the climate in that room.

If you can't grasp that then relative humidity is really going to jam those wheel cogs.

There are times when too much info is overload. The grey matter is jammed......How'd ya know ?

[WDH]

This is when you turn the thread to food  .

[Magicman]

Danny, I'm gonna have to feed you real soon.....

[WDH]

Success  .

[ihookem]

I got a bunch of Black locust today. If you can get it to grow fast it might be worth planting if you can get seedlings cheap. It was very heavy wood but also holds a lot of moisture. The Ash was much lighter but drier.